Refereed Publications with NCAR Authors and Abstracts

MOPITT Refereed Publications with NCAR authors

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Publication Count by Year


Aragão, L. E. O. C., L. O. Anderson, M. G. Fonseca, T. M. Rosan, L. B. Vedovato, F. H. Wagner, C. V. J. Silva, C. H. L. S. Junior, E. Arai, A. P. Aguiar, J. Barlow, E. Berenguer, M. N. Deeter, L. G. Domingues, L. Gatti, M. Gloor, Y. Malhi, J. A. Marengo, J. B. Miller, O. L. Phillips, and S. Saatchi (2018), 21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions, Nature Communications, 9(1), 536, doi:10.1038/s41467-017-02771-y.
Deforestation carbon emissions from the Brazilian Amazon have declined steeply, but how much drought-induced forest fire emissions add to this process is still unclear. Here the authors show that gross emissions from forest fires are more than half as great as those from deforestation during drought years.
Buchholz, R. R., D. Hammerling, H. M. Worden, M. N. Deeter, L. K. Emmons, D. P. Edwards, and S. A. Monks (2018), Links Between Carbon Monoxide and Climate Indices for the Southern Hemisphere and Tropical Fire Regions, J. Geophys. Res.-Atmos., 123(17), 9786–9800, doi:10.1029/2018JD028438.
In the Southern Hemisphere and tropics, the main contribution to carbon monoxide (CO) variability is from fire emissions, which are connected to climate through the availability, type, and dryness of fuel. Here we assess the data-driven relationships between CO and climate, aiming to predict atmospheric loading during fire seasons. Observations of total column CO from the Measurements Of Pollution In The Troposphere satellite instrument are used to build a record of monthly anomalies between 2001 and 2016, focusing on seven biomass burning regions of the Southern Hemisphere and tropics. With the exception of 2015, the range of absolute variability in CO is similar between regions. We model CO anomalies in each of the regions using climate indices for the climate modes: El Nino-Southern Oscillation, Indian Ocean Dipole, Tropical South Atlantic, and Antarctic Oscillation. Stepwise forward and backward variable selection is used to choose from statistical regression models that use combinations of climate indices, at lag times between 1 and 8months relative to CO anomalies. The Bayesian information criterion selects models with the best predictive power. We find that all climate mode indices are required to model CO in each region, generally explaining over 50% of the variability and over 70% for tropical regions. First-order interaction terms of the climate modes are necessary, producing greatly improved explanation of CO variability over single terms. Predictive capability is assessed for the Maritime Southeast Asia and the predicted peak CO anomaly in 2015 is within 20% of the measurements.
Deeter, M. N., S. Martínez‐Alonso, M. O. Andreae, and H. Schlager (2018), Satellite-Based Analysis of CO Seasonal and Interannual Variability Over the Amazon Basin, Journal of Geophysical Research: Atmospheres, 0(0), doi:10.1029/2018JD028425. [online] Available from: .
The “Measurements of Pollution in the Troposphere” (MOPITT) satellite record is applied to study the geographical and temporal variability of carbon monoxide (CO) from biomass burning in the Amazon Basin. The presented analysis demonstrates the use of satellite observations for interpreting the effects of deforestation and climate on past and future emissions of CO. The study exploits the MOPITT “multispectral” retrieval product which effectively resolves tropospheric CO into two independently measured layers. New validation results based on in situ measurements during the ACRIDICON-CHUVA aircraft campaign in 2014 are used for bias correction. Contrasting CO monthly climatologies are presented for the Amazon Basin for the lower and upper troposphere (“LT” and “UT”) with an emphasis on the Amazonian dry season. Climatologically, spatial patterns of UT CO over the Amazon Basin appear to be related to both deep convection and anticyclonic flow. Strongly enhanced LT basin-mean CO concentrations are observed for the dry season months in 2005, 2007, 2010, and 2015, while the record also indicates a decreasing long-term trend. These observations are consistent with the expected effects of falling deforestation rates since 2004, punctuated by CO spikes in drought years due to large-scale wildfires.
Edwards, D. P., H. M. Worden, D. Neil, G. Francis, T. Valle, and A. F. Arellano (2018), The CHRONOS mission: capability for sub-hourly synoptic observations of carbon monoxide and methane to quantify emissions and transport of air pollution, Atmos. Meas. Tech., 11(2), 1061–1085, doi:10.5194/amt-11-1061-2018.
The CHRONOS space mission concept provides time-resolved abundance for emissions and transport studies of the highly variable and highly uncertain air pollutants carbon monoxide and methane, with sub-hourly revisit rate at fine (similar to 4 km) horizontal spatial resolution across a North American domain. CHRONOS can provide complete synoptic air pollution maps (“snapshots”) of the continental domain with less than 10 min of observations. This rapid mapping enables visualization of air pollution transport simultaneously across the entire continent and enables a sentinel-like capability for monitoring evolving, or unanticipated, air pollution sources in multiple locations at the same time with high temporal resolution. CHRONOS uses a compact imaging gas filter correlation radiometer for these observations, with heritage from more than 17 years of scientific data and algorithm advances by the science teams for the Measurements of Pollution in the Troposphere (MOPITT) instrument on NASA’s Terra spacecraft in low Earth orbit. To achieve continental-scale sub-hourly sampling, the CHRONOS mission would be conducted from geostationary orbit, with the instrument hosted on a communications or meteorological platform. CHRONOS observations would contribute to an integrated observing system for atmospheric composition using surface, suborbital and satellite data with atmospheric chemistry models, as defined by the Committee on Earth Observing Satellites. Addressing the U.S. National Academy’s 2007 decadal survey direction to characterize diurnal changes in tropospheric composition, CHRONOS observations would find direct societal applications for air quality management and forecasting to protect public health.
Jiang, Z., B. C. McDonald, H. Worden, J. R. Worden, K. Miyazaki, Z. Qu, D. K. Henze, D. B. A. Jones, A. F. Arellano, E. V. Fischer, L. Zhu, and K. F. Boersma (2018), Unexpected slowdown of US pollutant emission reduction in the past decade, PNAS, 201801191, doi:10.1073/pnas.1801191115.
Ground and satellite observations show that air pollution regulations in the United States (US) have resulted in substantial reductions in emissions and corresponding improvements in air quality over the last several decades. However, large uncertainties remain in evaluating how recent regulations affect different emission sectors and pollutant trends. Here we show a significant slowdown in decreasing US emissions of nitrogen oxides (NOx) and carbon monoxide (CO) for 2011–2015 using satellite and surface measurements. This observed slowdown in emission reductions is significantly different from the trend expected using US Environmental Protection Agency (EPA) bottom-up inventories and impedes compliance with local and federal agency air-quality goals. We find that the difference between observations and EPA’s NOx emission estimates could be explained by: (i) growing relative contributions of industrial, area, and off-road sources, (ii) decreasing relative contributions of on-road gasoline, and (iii) slower than expected decreases in on-road diesel emissions.
Miyazaki, K., T. Sekiya, D. Fu, K. W. Bowman, S. S. Kulawik, K. Sudo, T. Walker, Y. Kanaya, M. Takigawa, K. Ogochi, H. Eskes, K. F. Boersma, A. M. Thompson, B. Gaubert, J. Barre, and L. K. Emmons (2018), Balance of emission and dynamical controls on ozone during KORUS-AQ from multi-constituent satellite data assimilation, Journal of Geophysical Research: Atmospheres, 0(ja), doi:10.1029/2018JD028912. [online] Available from: .
Global multi-constituent concentration and emission fields obtained from the assimilation of the satellite retrievals of ozone, CO, NO2, HNO3, and SO2 from OMI, GOME-2, MOPITT, MLS, and AIRS/OMI are used to understand the processes controlling air pollution during the Korea U.S.-Air Quality (KORUS-AQ) campaign. Estimated emissions in South Korea were 0.42 TgN for NOx and 1.1 TgCO for CO, which were 40% and 83% higher, respectively, than the a priori bottom-up inventories, and increased mean ozone concentration by up to 7.5±1.6 ppbv. The observed boundary layer ozone exceeded 90 ppbv over Seoul under stagnant phases, whereas it was approximately 60 ppbv during dynamical conditions given equivalent emissions. Chemical reanalysis showed that mean ozone concentration was persistently higher over Seoul (75.10±7.6 ppbv) than the broader KORUS-AQ domain (70.5±9.2 ppbv) at 700 hPa. Large bias reductions (>75%) in the free tropospheric OH show that multiple-species assimilation is critical for balanced tropospheric chemistry analysis and emissions. The assimilation performance was dependent on the particular phase. While the evaluation of data assimilation fields shows an improved agreement with aircraft measurements in ozone (to less than 5 ppbv biases), CO, NO2, SO2, PAN, and OH profiles, lower tropospheric ozone analysis error was largest at stagnant conditions, whereas the model errors were mostly removed by data assimilation under dynamic weather conditions. Assimilation of new AIRS/OMI ozone profiles allowed for additional error reductions, especially under dynamic weather conditions. Our results show the important balance of dynamics and emissions both on pollution and the chemical assimilation system performance.
Mizzi, Arthur P., Edwards D. P., and Anderson J. L. (2018), Assimilating compact phase space retrievals (CPSRs): comparison with independent observations (MOZAIC in situ and IASI retrievals) and extension to assimilation of truncated retrieval profiles., Geoscientific Model Development, 11(9), p3727-3745.
Assimilation of atmospheric composition retrievals presents computational challenges due to their high data volume and often sparse information density. Assimilation of compact phase space retrievals (CPSRs) meets those challenges and offers a promising alternative to assimilation of raw retrievals at reduced computational cost (Mizzi et al., 2016). This paper compares analysis and forecast results from assimilation of Terra/Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO) CPSRs with independent observations. We use MetOp-A/Infrared Atmospheric Sounding Interferometer (IASI) CO retrievals and Measurement of OZone, water vapor, carbon monoxide, and nitrogen oxides by in-service AIrbus airCraft (MOZAIC) in situ CO profiles for our independent observation comparisons. Generally, the results confirm that assimilation of MOPITT CPSRs improves the Weather Research and Forecasting model with chemistry coupled to the ensemble Kalman filter data assimilation from the Data Assimilation Research Testbed (WRF-Chem/DART) analysis fit and forecast skill at a reduced computational cost compared to assimilation of raw retrievals. Comparison with the independent observations shows that assimilation of MOPITT CO generally improved the analysis fit and forecast skill in the lower troposphere but degraded it in the upper troposphere. We attribute that degradation to assimilation of MOPITT CO retrievals with a possible bias of ~ 14% above 300 hPa. To discard the biased retrievals, in this paper, we also extend CPSRs to assimilation of truncated retrieval profiles (as opposed to assimilation of full retrieval profiles). Those results show that not assimilating the biased retrievals (i) resolves the upper tropospheric analysis fit degradation issue and (ii) reduces the impact of assimilating the remaining unbiased retrievals because the total information content and vertical sensitivities are changed.
Nechita-Banda, N., M. Krol, G. R. van der Werf, J. W. Kaiser, S. Pandey, V. Huijnen, C. Clerbaux, P. Coheur, M. N. Deeter, and T. Rockmann (2018), Monitoring emissions from the 2015 Indonesian fires using CO satellite data, Philos. Trans. R. Soc. B-Biol. Sci., 373(1760), 20170307, doi:10.1098/rstb.2017.0307.
Southeast Asia, in particular Indonesia, has periodically struggled with intense fire events. These events convert substantial amounts of carbon stored as peat to atmospheric carbon dioxide (CO2) and significantly affect atmospheric composition on a regional to global scale. During the recent 2015 El Nino event, peat fires led to strong enhancements of carbon monoxide (CO), an air pollutant and well-known tracer for biomass burning. These enhancements were clearly observed from space by the Infrared Atmospheric Sounding Interferometer (IASI) and the Measurements of Pollution in the Troposphere (MOPITT) instruments. We use these satellite observations to estimate CO fire emissions within an inverse modelling framework. We find that the derived CO emissions for each sub-region of Indonesia and Papua are substantially different from emission inventories, highlighting uncertainties in bottom-up estimates. CO fire emissions based on either MOPITT or IASI have a similar spatial pattern and evolution in time, and a 10% uncertainty based on a set of sensitivity tests we performed. Thus, CO satellite data have a high potential to complement existing operational fire emission estimates based on satellite observations of fire counts, fire radiative power and burned area, in better constraining fire occurrence and the associated conversion of peat carbon to atmospheric CO2. A total carbon release to the atmosphere of 0.35-0.60 Pg C can be estimated based on our results. This article is part of a discussion meeting issue “The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications”.
Zheng, B., F. Chevallier, P. Ciais, Y. Yin, M. N. Deeter, H. M. Worden, Y. Wang, Qiang Zhang, and K. He (2018), Rapid decline in carbon monoxide emissions and export from East Asia between years 2005 and 2016, Environ. Res. Lett., 13(4), 044007, doi:10.1088/1748-9326/aab2b3.
Measurements of Pollution in the Troposphere (MOPITT) satellite and ground-based carbon monoxide (CO) measurements both suggest a widespread downward trend in CO concentrations over East Asia during the period 2005–2016. This negative trend is inconsistent with global bottom-up inventories of CO emissions, which show a small increase or stable emissions in this region. We try to reconcile the observed CO trend with emission inventories using an atmospheric inversion of the MOPITT CO data that estimates emissions from primary sources, secondary production, and chemical sinks of CO. The atmospheric inversion indicates a −2% yr −1 decrease in emissions from primary sources in East Asia from 2005–2016. The decreasing emissions are mainly caused by source reductions in China. The regional MEIC inventory for China is the only bottom up estimate consistent with the inversion-diagnosed decrease of CO emissions. According to the MEIC data, decreasing CO emissions from four main sectors (iron and steel industries, residential sources, gasoline-powered vehicles, and construction materials industries) in China explain 76% of the inversion-based trend of East Asian CO emissions. This result suggests that global inventories underestimate the recent decrease of CO emission factors in China which occurred despite increasing consumption of carbon-based fuels, and is driven by rapid technological changes with improved combustion efficiency and emission control measures.


Buchholz, R. R., M. N. Deeter, H. M. Worden, J. Gille, D. P. Edwards, J. W. Hannigan, N. B. Jones, C. Paton-Walsh, D. W. T. Griffith, D. Smale, J. Robinson, K. Strong, S. Conway, R. Sussmann, F. Hase, T. Blumenstock, E. Mahieu, and B. Langerock (2017), Validation of MOPITT carbon monoxide using ground-based Fourier transform infrared spectrometer data from NDACC, Atmos. Meas. Tech., 10(5), 1927–1956, doi:10.5194/amt-10-1927-2017.
The Measurements of Pollution in the Troposphere (MOPITT) satellite instrument provides the longest continuous dataset of carbon monoxide (CO) from space. We perform the first validation of MOPITT version 6 retrievals using total column CO measurements from ground-based remote-sensing Fourier transform infrared spectrometers (FTSs). Validation uses data recorded at 14 stations, that span a wide range of latitudes (80 degrees N to 78 degrees S), in the Network for the Detection of Atmospheric Composition Change (NDACC). MOPITT measurements are spatially co-located with each station, and different vertical sensitivities between instruments are accounted for by using MOPITT averaging kernels (AKs). All three MOPITT retrieval types are analyzed: thermal infrared (TIR-only), joint thermal and near infrared (TIR-NIR), and near infrared (NIR-only). Generally, MOPITT measurements overestimate CO relative to FTS measurements, but the bias is typically less than 10 %. Mean bias is 2.4% for TIR-only, 5.1% for TIR-NIR, and 6.5% for NIR-only. The TIR-NIR and NIR-only products consistently produce a larger bias and lower correlation than the TIR-only. Validation performance of MOPITT for TIR-only and TIR-NIR retrievals over land or water scenes is equivalent. The four MOPITT detector element pixels are validated separately to account for their different uncertainty characteristics. Pixel 1 produces the highest standard deviation and lowest correlation for all three MOPITT products. However, for TIR-only and TIR-NIR, the error-weighted average that includes all four pixels often provides the best correlation, indicating compensating pixel biases and well-captured error characteristics. We find that MOPITT bias does not depend on latitude but rather is influenced by the proximity to rapidly changing atmospheric CO. MOPITT bias drift has been bound geographically to within +/- 0.5% yr 1 or lower at almost all locations.
Deeter, M. N., D. P. Edwards, G. L. Francis, J. C. Gille, S. Martinez-Alonso, H. M. Worden, and C. Sweeney (2017), A Climate-scale Satellite Record for Carbon Monoxide: The MOPITT Version 7 Product, Atmos. Meas. Tech. Discuss., 2017, 1–34, doi:10.5194/amt-2017-71.
The MOPITT (“Measurements of Pollution in the Troposphere”) satellite instrument has been making observations of atmospheric carbon monoxide since 2000. Recent enhancements to the MOPITT retrieval algorithm have resulted in the release of the Version 7 (V7) product. Improvements include (1) representation of growing atmospheric concentrations of N2O, (2) use of meteorological fields from the MERRA-2 reanalysis for the entire MOPITT mission (instead of MERRA), (3) use of the MODIS Collection 6 cloud mask product (instead of Collection 5), (4) a new strategy for radiance bias correction, and (5) an improved method for calibrating MOPITT’s NIR radiances. Statistical comparisons of V7 validation results with corresponding V6 results are presented, using aircraft in-situ measurements as the reference. Clear improvements are demonstrated for V7 products with respect to overall retrieval biases, bias variability, and bias drift uncertainty.
Dekker, I. N., S. Houweling, I. Aben, T. Röckmann, M. Krol, S. Martínez-Alonso, M. N. Deeter, and H. M. Worden (2017), Quantification of CO emissions from the city of madrid using MOPITT satellite retrievals and WRF simulations, Atmospheric Chemistry and Physics, 17(23), 14675–14694, doi:10.5194/acp-17-14675-2017.
<p>The growth of mega-cities leads to air quality problems directly affecting the citizens. Satellite measurements are becoming of higher quality and quantity, which leads to more accurate satellite retrievals of enhanced air pollutant concentrations over large cities. In this paper, we compare and discuss both an existing and a new method for estimating urban-scale trends in CO emissions using multiyear retrievals from the MOPITT satellite instrument. The first method is mainly based on satellite data, and has the advantage of fewer assumptions, but also comes with uncertainties and limitations as shown in this paper. To improve the reliability of urban-To-regional scale emission trend estimation, we simulate MOPITT retrievals using the Weather Research and Forecast model with chemistry core (WRFChem). The difference between model and retrieval is used to optimize CO emissions in WRF-Chem, focusing on the city of Madrid, Spain. This method has the advantage over the existing method in that it allows both a trend analysis of CO concentrations and a quantification of CO emissions. Our analysis confirms that MOPITT is capable of detecting CO enhancements over Madrid, although significant differences remain between the yearly averaged model output and satellite measurements (R2 D0.75) over the city. After optimization, we find Madrid CO emissions to be lower by 48% for 2002 and by 17% for 2006 compared with the EdgarV4.2 emission inventory. The MOPITT-derived emission adjustments lead to better agreement with the European emission inventory TNO-MAC-III for both years. This suggests that the downward trend in CO emissions over Madrid is overestimated in EdgarV4.2 and more realistically represented in TNO-MACC-III. However, our satellite and model based emission estimates have large uncertainties, around 20% for 2002 and 50% for 2006.</p>
Gaubert, B., H. M. Worden, A. F. J. Arellano, L. K. Emmons, S. Tilmes, J. Barre, S. M. Alonso, F. Vitt, J. L. Anderson, F. Alkemade, S. Houweling, and D. P. Edwards (2017), Chemical Feedback From Decreasing Carbon Monoxide Emissions, Geophys. Res. Lett., 44(19), 9985–9995, doi:10.1002/2017GL074987.
Understanding changes in the burden and growth rate of atmospheric methane (CH4) has been the focus of several recent studies but still lacks scientific consensus. Here we investigate the role of decreasing anthropogenic carbon monoxide (CO) emissions since 2002 on hydroxyl radical (OH) sinks and tropospheric CH4 loss. We quantify this impact by contrasting two model simulations for 2002-2013: (1) a Measurement of the Pollution in the Troposphere (MOPITT) CO reanalysis and (2) a Control-Run without CO assimilation. These simulations are performed with the Community Atmosphere Model with Chemistry of the Community Earth System Model fully coupled chemistry climate model with prescribed CH4 surface concentrations. The assimilation of MOPITT observations constrains the global CO burden, which significantly decreased over this period by similar to 20%. We find that this decrease results to (a) increase in CO chemical production, (b) higher CH4 oxidation by OH, and (c) similar to 8% shorter CH4 lifetime. We elucidate this coupling by a surrogate mechanism for CO-OH-CH4 that is quantified from the full chemistry simulations.
Jiang, Z., J. R. Worden, H. Worden, M. Deeter, D. B. A. Jones, A. F. Arellano, and D. K. Henze (2017), A 15-year record of CO emissions constrained by MOPITT CO observations, Atmos. Chem. Phys., 17(7), 4565–4583, doi:10.5194/acp-17-4565-2017.
Long-term measurements from satellites and surface stations have demonstrated a decreasing trend of tropospheric carbon monoxide (CO) in the Northern Hemisphere over the past decade. Likely explanations for this decrease include changes in anthropogenic, fires, and/or biogenic emissions or changes in the primary chemical sink hydroxyl radical (OH). Using remotely sensed CO measurements from the Measurement of Pollution in the Troposphere (MOPITT) satellite instrument, in situ methyl chloroform (MCF) measurements from the World Data Centre for Greenhouse Gases (WDCGG) and the adjoint of the GEOS-Chem model, we estimate the change in global CO emissions from 2001 to 2015. We show that the loss rate of MCF varied by 0.2 % in the past 15 years, indicating that changes in global OH distributions do not explain the recent decrease in CO. Our two-step inversion approach for estimating CO emissions is intended to mitigate the effect of bias errors in the MOPITT data as well as model errors in transport and chemistry, which are the primary factors contributing to the uncertainties when quantifying CO emissions using these remotely sensed data. Our results confirm that the decreasing trend of tropospheric CO in the Northern Hemisphere is due to decreasing CO emissions from anthropogenic and biomass burning sources. In particular, we find decreasing CO emissions from the United States and China in the past 15 years, and unchanged anthropogenic CO emissions from Europe since 2008. We find decreasing trends of biomass burning CO emissions from boreal North America, boreal Asia and South America, but little change over Africa. In contrast to prior results, we find that a positive trend in CO emissions is likely for India and southeast Asia.
Kulawik, S. S., C. O’Dell, V. H. Payne, L. Kuai, H. M. Worden, S. C. Biraud, C. Sweeney, B. Stephens, L. T. Iraci, E. L. Yates, and T. Tanaka (2017), Lower-tropospheric CO2 from near-infrared ACOS-GOSAT observations, Atmos. Chem. Phys., 17(8), 5407–5438, doi:10.5194/acp-17-5407-2017.
We present two new products from near-infrared Greenhouse Gases Observing Satellite (GOSAT) observations: lowermost tropospheric (LMT, from 0 to 2.5 km) and upper tropospheric-stratospheric (U, above 2.5 km) carbon dioxide partial column mixing ratios. We compare these new products to aircraft profiles and remote surface flask measurements and find that the seasonal and year-to-year variations in the new partial column mixing ratios significantly improve upon the Atmospheric CO2 Observations from Space (ACOS) and GOSAT (ACOS-GOSAT) initial guess and/or a priori, with distinct patterns in the LMT and U seasonal cycles that match validation data. For land monthly averages, we find errors of 1.9, 0.7, and 0.8 ppm for retrieved GOSAT LMT, U, and X CO2; for ocean monthly averages, we find errors of 0.7, 0.5, and 0.5 ppm for retrieved GOSAT LMT, U, and X CO2. In the southern hemispheric biomass burning season, the new partial columns show similar patterns to MODIS fire maps and MOPITT multispectral CO for both vertical levels, despite a flat ACOS-GOSAT prior, and a CO-CO2 emission factor comparable to published values. The difference of LMT and U, useful for evaluation of model transport error, has also been validated with a monthly average error of 0.8 (1.4) ppm for ocean (land). LMT is more locally influenced than U, meaning that local fluxes can now be better separated from CO2 transported from far away.
Mok, J., S. S. Park, H. Lim, J. Kim, D. Edwards, J. Lee, J. Yoon, Y. G. Lee, and J.-H. Koo (2017a), Correlation analysis between regional carbon monoxide and black carbon from satellite measurements, Atmospheric Research, doi:10.1016/j.atmosres.2017.04.004. [online] Available from: .
In this study, we present and compare regional correlations between CO total column density (TCDCO) from the data set of Measurement of Pollution in the Troposphere (MOPITT), and high-absorbing BC dominant aerosol optical depth (AODBC) from the retrieval algorithm using Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) (MODIS-OMI algorithm, MOA). TCDCO shows positive relationship to both fine-mode AOD (AODFM) and AODBC in general, but TCDCO better correlates with AODBC than AODFM. This enhanced correlation between TCDCO and AODBC appears more clearly during spring and summer. Correlation between TCDCO and AODBC is exceptionally poor in Northern Africa where the BC-dominated aerosols are frequently mixed with mineral dust particles from the Sahara. Another issue is also found in Southern Africa; the correlation between AODBC and TCDCO in this region is not much higher than that between the AODFM and TCDCO in spite of large occurrence of biomass burning and wildfire. This can be explained by the cloud perturbation near the source regions and dispersion effect due to the typical wind pattern. Correlations between AODBC and TCDCO increase further when fire detected areas are only considered, but does not change much over the urban area. This difference clarifies the large contribution of burning events to the positive relationship between BC and CO. All findings in this study demonstrate a possible use of satellite CO product in evaluating the BC-dominated aerosol product from satellite remote sensing over the globe.
Mok, J., S. S. Park, H. Lim, J. Kim, D. P. Edwards, J. Lee, J. Yoon, Y. G. Lee, and J.-H. Koo (2017b), Correlation analysis between regional carbon monoxide and black carbon from satellite measurements, Atmos. Res., 196, 29–39, doi:10.1016/j.atmosres.2017.04.004.
In this study, we present and compare regional correlations between CO total column density (TCDco) from the data set of Measurement of Pollution in the Troposphere (MOPITT), and high-absorbing BC dominant aerosol optical depth (AOD(Bc)) from the retrieval algorithm using Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) (MODIS-OMI algorithm, MOA). TCDco shows positive relationship to both fine -mode AOD (AOD(Fm)) and AODBc in general, but TCDco better correlates with AODBc than AODFm. This enhanced correlation between TCDco and AODBc appears more clearly during spring and summer. Correlation between TCDco and AODBc is exceptionally poor in Northern Africa where the BC dominated aerosols are frequently mixed with mineral dust particles from the Sahara. Another issue is also found in Southern Africa; the correlation between AODBc and TCDco in this region is not much higher than that between the AODFm and TCDco in spite of large occurrence of biomass burning and wildfire. This can be explained by the cloud perturbation near the source regions and dispersion effect due to the typical wind pattern. Correlations between AODBc and TCDco increase further when fire detected areas are only considered, but does not change much over the urban area. This difference clarifies the large contribution of burning events to the positive relationship between BC and CO. All findings in this study demonstrate a possible use of satellite CO product in evaluating the BC-dominated aerosol product from satellite remote sensing over the globe.
Worden, J. R., A. A. Bloom, S. Pandey, Z. Jiang, H. M. Worden, T. W. Walker, S. Houweling, and T. Rockmann (2017), Reduced biomass burning emissions reconcile conflicting estimates of the post-2006 atmospheric methane budget, Nat. Commun., 8, 2227, doi:10.1038/s41467-017-02246-0.
Several viable but conflicting explanations have been proposed to explain the recent similar to 8 p.p.b. per year increase in atmospheric methane after 2006, equivalent to net emissions increase of similar to 25 Tg CH4 per year. A concurrent increase in atmospheric ethane implicates a fossil source; a concurrent decrease in the heavy isotope content of methane points toward a biogenic source, while other studies propose a decrease in the chemical sink (OH). Here we show that biomass burning emissions of methane decreased by 3.7 (+/- 1.4) Tg CH4 per year from the 2001-2007 to the 2008-2014 time periods using satellite measurements of CO and CH4, nearly twice the decrease expected from prior estimates. After updating both the total and isotopic budgets for atmospheric methane with these revised biomass burning emissions (and assuming no change to the chemical sink), we find that fossil fuels contribute between 12-19 Tg CH4 per year to the recent atmospheric methane increase, thus reconciling the isotopic-and ethane-based results.


Deeter, M. N., S. Martínez-Alonso, L. V. Gatti, M. Gloor, J. B. Miller, L. G. Domingues, and C. S. C. Correia (2016), Validation and analysis of MOPITT CO observations of the Amazon Basin, Atmos. Meas. Tech., 9(8), 3999–4012, doi:10.5194/amt-9-3999-2016.
We analyze satellite retrievals of carbon monoxide from the MOPITT (Measurements of Pollution in the Troposphere) instrument over the Amazon Basin, focusing on the MOPITT Version 6 “multispectral” retrieval product (exploiting both thermal-infrared and near-infrared channels). Validation results based on in situ vertical profiles measured between 2010 and 2013 are presented for four sites in the Amazon Basin. Results indicate a significant negative bias in retrieved lower-tropospheric CO concentrations. The possible influence of smoke aerosol as a source of retrieval bias is investigated using collocated Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) measurements at two sites but does not appear to be significant. Finally, we exploit the MOPITT record to analyze both the mean annual cycle and the interannual variability of CO over the Amazon Basin since 2002.
Field, R. D., G. R. van der Werf, T. Fanin, E. J. Fetzer, R. Fuller, H. Jethva, R. Levy, N. J. Livesey, M. Luo, O. Torres, and H. M. Worden (2016), Indonesian fire activity and smoke pollution in 2015 show persistent nonlinear sensitivity to El Nino-induced drought, Proc. Natl. Acad. Sci. U. S. A., 113(33), 9204–9209, doi:10.1073/pnas.1524888113.
The 2015 fire season and related smoke pollution in Indonesia was more severe than the major 2006 episode, making it the most severe season observed by the NASA Earth Observing System satellites that go back to the early 2000s, namely active fire detections from the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS), MODIS aerosol optical depth, Terra Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO), Aqua Atmospheric Infrared Sounder (AIRS) CO, Aura Ozone Monitoring Instrument (OMI) aerosol index, and Aura Microwave Limb Sounder (MLS) CO. The MLS CO in the upper troposphere showed a plume of pollution stretching from East Africa to the western Pacific Ocean that persisted for 2 mo. Longer-term records of airport visibility in Sumatra and Kalimantan show that 2015 ranked after 1997 and alongside 1991 and 1994 as among the worst episodes on record. Analysis of yearly dry season rainfall from the Tropical Rainfall Measurement Mission (TRMM) and rain gauges shows that, due to the continued use of fire to clear and prepare land on degraded peat, the Indonesian fire environment continues to have nonlinear sensitivity to dry conditions during prolonged periods with less than 4 mm/d of precipitation, and this sensitivity appears to have increased over Kalimantan. Without significant reforms in land use and the adoption of early warning triggers tied to precipitation forecasts, these intense fire episodes will reoccur during future droughts, usually associated with El Nino events.
Fu, D., K. W. Bowman, H. M. Worden, V. Natraj, J. R. Worden, S. Yu, P. Veefkind, I. Aben, J. Landgraf, L. Strow, and Y. Han (2016), High-resolution tropospheric carbon monoxide profiles retrieved from CrIS and TROPOMI, Atmos. Meas. Tech., 9(6), 2567–2579, doi:10.5194/amt-9-2567-2016.
The Measurements of Pollution in the Troposphere (MOPITT) instrument is the only satellite-borne sensor in operation that uses both thermal (TIR) and near-infrared (NIR) channels to estimate CO profiles. With more than 15 years (2000 to present) of validated multispectral observations, MOPITT provides the unique capability to separate CO in the lowermost troposphere (LMT, surface to 3 km (similar to 700 hPa)) from the free-tropospheric abundance. To extend this record, a new, hyper-spectral approach is presented here that will provide CO data products exceeding the capabilities of MOPITT by combining the short-wavelength infrared (SWIR, equivalent to the MOPITT NIR) channels from the TROPOspheric Monitoring Instrument (TROPOMI) to be launched aboard the European Sentinel 5 Precursor (S5p) satellite in 2016 and the TIR channels from the Cross-track Infrared Sounder (CrIS) aboard the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite. We apply the MUlti-SpEctra, MUlti-SpEcies, Multi-SEnsors (MUSES) retrieval algorithm to quantify the potential of this joint CO product. CO profiles are retrieved from a single-footprint, full-spectral-resolution CrIS transect over Africa on 27-28 August 2013 coincident with significant biomass burning. Comparisons of collocated CrIS and MOPITT CO observations for the LMT show a mean difference of 2.8 +/- 24.9 ppb, which is well within the estimated measurement uncertainty of both sensors. The estimated degrees of freedom (DOF) for CO signals from synergistic CrIS-TROPOMI retrievals are approximately 0.9 in the LMT and 1.3 above the LMT, which indicates that the LMT CO can be distinguished from the free troposphere, similar to MOPITT multispectral observations (0.8 in the LMT, and 1.1 above the LMT). In addition to increased sensitivity, the combined retrievals reduce measurement uncertainty, with similar to 15% error reduction in the LMT. With a daily global coverage and a combined spatial footprint of 14 km, the joint CrIS-TROPOMI measurements have the potential to extend and improve upon the MOPITT multispectral CO data records for the coming decade.
Gaubert, B., A. F. Arellano, J. Barré, H. M. Worden, L. K. Emmons, S. Tilmes, R. R. Buchholz, F. Vitt, K. Raeder, N. Collins, J. L. Anderson, C. Wiedinmyer, S. Martinez Alonso, D. P. Edwards, M. O. Andreae, J. W. Hannigan, C. Petri, K. Strong, and N. Jones (2016), Toward a chemical reanalysis in a coupled chemistry-climate model: An evaluation of MOPITT CO assimilation and its impact on tropospheric composition, J. Geophys. Res. Atmos., 121(12), 2016JD024863, doi:10.1002/2016JD024863.
We examine in detail a 1 year global reanalysis of carbon monoxide (CO) that is based on joint assimilation of conventional meteorological observations and Measurement of Pollution in The Troposphere (MOPITT) multispectral CO retrievals in the Community Earth System Model (CESM). Our focus is to assess the impact to the chemical system when CO distribution is constrained in a coupled full chemistry-climate model like CESM. To do this, we first evaluate the joint reanalysis (MOPITT Reanalysis) against four sets of independent observations and compare its performance against a reanalysis with no MOPITT assimilation (Control Run). We then investigate the CO burden and chemical response with the aid of tagged sectoral CO tracers. We estimate the total tropospheric CO burden in 2002 (from ensemble mean and spread) to be 371 ± 12% Tg for MOPITT Reanalysis and 291 ± 9% Tg for Control Run. Our multispecies analysis of this difference suggests that (a) direct emissions of CO and hydrocarbons are too low in the inventory used in this study and (b) chemical oxidation, transport, and deposition processes are not accurately and consistently represented in the model. Increases in CO led to net reduction of OH and subsequent longer lifetime of CH4 (Control Run: 8.7 years versus MOPITT Reanalysis: 9.3 years). Yet at the same time, this increase led to 5–10% enhancement of Northern Hemisphere O3 and overall photochemical activity via HOx recycling. Such nonlinear effects further complicate the attribution to uncertainties in direct emissions alone. This has implications to chemistry-climate modeling and inversion studies of longer-lived species.
Hoshyaripour, G., G. Brasseur, M. F. Andrade, M. Gavidia-Calderón, I. Bouarar, and R. Y. Ynoue (2016), Prediction of ground-level ozone concentration in São Paulo, Brazil: Deterministic versus statistic models, Atmospheric Environment, 145, 365–375, doi:10.1016/j.atmosenv.2016.09.061.
Two state-of-the-art models (deterministic: Weather Research and Forecast model with Chemistry (WRF-Chem) and statistic: Artificial Neural Networks: (ANN)) are implemented to predict the ground-level ozone concentration in São Paulo (SP), Brazil. Two domains are set up for WRF-Chem simulations: a coarse domain (with 50 km horizontal resolution) including whole South America (D1) and a nested domain (with horizontal resolution of 10 km) including South Eastern Brazil (D2). To evaluate the spatial distribution of the chemical species, model results are compared to the Measurements of Pollution in The Troposphere (MOPITT) data, showing that the model satisfactorily predicts the CO concentrations in both D1 and D2. The model also reproduces the measurements made at three air quality monitoring stations in SP with the correlation coefficients of 0.74, 0.70, and 0.77 for O3 and 0.51, 0.48, and 0.57 for NOx. The input selection for ANN model is carried out using Forward Selection (FS) method. FS-ANN is then trained and validated using the data from two air quality monitoring stations, showing correlation coefficients of 0.84 and 0.75 for daily mean and 0.64 and 0.67 for daily peak ozone during the test stage. Then, both WRF-Chem and FS-ANN are deployed to forecast the daily mean and peak concentrations of ozone in two stations during 5–20 August 2012. Results show that WRF-Chem preforms better in predicting mean and peak ozone concentrations as well as in conducting mechanistic and sensitivity analysis. FS-ANN is only advantageous in predicting mean daily ozone concentrations considering its significantly lower computational costs and ease of development and implementation, compared to that of WRF-Chem.
Strode, S. A., H. M. Worden, M. Damon, A. R. Douglass, B. N. Duncan, L. K. Emmons, J.-F. Lamarque, M. Manyin, L. D. Oman, J. M. Rodriguez, S. E. Strahan, and S. Tilmes (2016), Interpreting space-based trends in carbon monoxide with multiple models, Atmos. Chem. Phys., 16(11), 7285–7294, doi:10.5194/acp-16-7285-2016.
We use a series of chemical transport model and chemistry climate model simulations to investigate the observed negative trends in MOPITT CO over several regions of the world, and to examine the consistency of time-dependent emission inventories with observations. We find that simulations driven by the MACCity inventory, used for the Chemistry Climate Modeling Initiative (CCMI), reproduce the negative trends in the CO column observed by MOPITT for 2000-2010 over the eastern United States and Europe. However, the simulations have positive trends over eastern China, in contrast to the negative trends observed by MOPITT. The model bias in CO, after applying MOPITT averaging kernels, contributes to the model-observation discrepancy in the trend over eastern China. This demonstrates that biases in a model’s average concentrations can influence the interpretation of the temporal trend compared to satellite observations. The total ozone column plays a role in determining the simulated tropospheric CO trends. A large positive anomaly in the simulated total ozone column in 2010 leads to a negative anomaly in OH and hence a positive anomaly in CO, contributing to the positive trend in simulated CO. These results demonstrate that accurately simulating variability in the ozone column is important for simulating and interpreting trends in CO.
Te, Y., P. Jeseck, B. Franco, E. Mahieu, N. Jones, C. Paton-Walsh, D. T. Griffith, R. R. Buchholz, J. Hadji-Lazaro, D. Hurtmans, and C. Janssen (2016), Seasonal variability of surface and column carbon monoxide over the megacity Paris, high-altitude Jungfraujoch and Southern Hemispheric Wollongong stations, Atmos. Chem. Phys., 16(17), 10911–10925, doi:10.5194/acp-16-10911-2016.
This paper studies the seasonal variation of surface and column CO at three different sites (Paris, Jungfraujoch and Wollongong), with an emphasis on establishing a link between the CO vertical distribution and the nature of CO emission sources. We find the first evidence of a time lag between surface and free tropospheric CO seasonal variations in the Northern Hemisphere. The CO seasonal variability obtained from the total columns and free tropospheric partial columns shows a maximum around March-April and a minimum around September-October in the Northern Hemisphere (Paris and Jungfraujoch). In the Southern Hemisphere (Wollongong) this seasonal variability is shifted by about 6 months. Satellite observations by the IASI-MetOp (Infrared Atmospheric Sounding Interferometer) and MOPITT (Measurements Of Pollution In The Troposphere) instruments confirm this seasonality. Ground-based FTIR (Fourier transform infrared) measurements provide useful complementary information due to good sensitivity in the boundary layer. In situ surface measurements of CO volume mixing ratios at the Paris and Jungfraujoch sites reveal a time lag of the near-surface seasonal variability of about 2 months with respect to the total column variability at the same sites. The chemical transport model GEOS-Chem (Goddard Earth Observing System chemical transport model) is employed to interpret our observations. GEOS-Chem sensitivity runs identify the emission sources influencing the seasonal variation of CO. At both Paris and Jungfraujoch, the surface seasonality is mainly driven by anthropogenic emissions, while the total column seasonality is also controlled by air masses transported from distant sources. At Wollongong, where the CO seasonality is mainly affected by biomass burning, no time shift is observed between surface measurements and total column data.


Barre, J., B. Gaubert, A. F. J. Arellano, H. M. Worden, D. P. Edwards, M. N. Deeter, J. L. Anderson, K. Raeder, N. Collins, S. Tilmes, G. Francois, C. Clerbaux, L. K. Emmons, G. G. Pfister, P.-F. Coheur, and D. Hurtmans (2015), Assessing the impacts of assimilating IASI and MOPITT CO retrievals using CESM-CAM-chem and DART, J. Geophys. Res.-Atmos., 120(19), doi:10.1002/2015JD023467.
We show the results and evaluation with independent measurements from assimilating both MOPITT (Measurements Of Pollution In The Troposphere) and IASI (Infrared Atmospheric Sounding Interferometer) retrieved profiles into the Community Earth System Model (CESM). We used the Data Assimilation Research Testbed ensemble Kalman filter technique, with the full atmospheric chemistry CESM component Community Atmospheric Model with Chemistry. We first discuss the methodology and evaluation of the current data assimilation system with coupled meteorology and chemistry data assimilation. The different capabilities of MOPITT and IASI retrievals are highlighted, with particular attention to instrument vertical sensitivity and coverage and how these impact the analyses. MOPITT and IASI CO retrievals mostly constrain the CO fields close to the main anthropogenic, biogenic, and biomass burning CO sources. In the case of IASI CO assimilation, we also observe constraints on CO far from the sources. During the simulation time period (June and July 2008), CO assimilation of both instruments strongly improves the atmospheric CO state as compared to independent observations, with the higher spatial coverage of IASI providing better results on the global scale. However, the enhanced sensitivity of multispectral MOPITT observations to near surface CO over the main source regions provides synergistic effects at regional scales.
Barré, J., D. Edwards, H. Worden, A. Da Silva, and W. Lahoz (2015), On the feasibility of monitoring carbon monoxide in the lower troposphere from a constellation of Northern Hemisphere geostationary satellites. (Part 1), Atmospheric Environment, 113, 63–77, doi:10.1016/j.atmosenv.2015.04.069.
By the end of the current decade, there are plans to deploy several geostationary Earth orbit (GEO) satellite missions for atmospheric composition over North America, East Asia and Europe with additional missions proposed. Together, these present the possibility of a constellation of geostationary platforms to achieve continuous time-resolved high-density observations over continental domains for mapping pollutant sources and variability at diurnal and local scales. In this paper, we use a novel approach to sample a very high global resolution model (GEOS-5 at 7 km horizontal resolution) to produce a dataset of synthetic carbon monoxide pollution observations representative of those potentially obtainable from a GEO satellite constellation with predicted measurement sensitivities based on current remote sensing capabilities. Part 1 of this study focuses on the production of simulated synthetic measurements for air quality OSSEs (Observing System Simulation Experiments). We simulate carbon monoxide nadir retrievals using a technique that provides realistic measurements with very low computational cost. We discuss the sampling methodology: the projection of footprints and areas of regard for geostationary geometries over each of the North America, East Asia and Europe regions; the regression method to simulate measurement sensitivity; and the measurement error simulation. A detailed analysis of the simulated observation sensitivity is performed, and limitations of the method are discussed. We also describe impacts from clouds, showing that the efficiency of an instrument making atmospheric composition measurements on a geostationary platform is dependent on the dominant weather regime over a given region and the pixel size resolution. These results demonstrate the viability of the “instrument simulator” step for an OSSE to assess the performance of a constellation of geostationary satellites for air quality measurements. We describe the OSSE results in a follow up paper (Part 2 of this study).
Bloom, A. A., J. Worden, Z. Jiang, H. Worden, T. Kurosu, C. Frankenberg, and D. Schimel (2015), Remote-sensing constraints on South America fire traits by Bayesian fusion of atmospheric and surface data, Geophys. Res. Lett., 42(4), 2014GL062584, doi:10.1002/2014GL062584.
Satellite observations reveal substantial burning during the 2007 and 2010 tropical South America fire season, with both years exhibiting similar total burned area. However, 2010 CO fire emissions, based on satellite CO concentration measurements, were substantially lower (−28%), despite the once-in-a-century drought in 2010. We use Bayesian inference with satellite measurements of CH4 and CO concentrations and burned area to quantify shifts in combustion characteristics in 2010 relative to 2007. We find an 88% probability in reduced combusted biomass density associated with the 2010 fires and an 82% probability of lower fire carbon losses in 2010 relative to 2007. Higher combustion efficiency was a smaller contributing factor to the reduced 2010 CO emissions. The reduction in combusted biomass density is consistent with a reduction (4–6%) in Global Ozone Monitoring Experiment 2 solar-induced fluorescence (a proxy for gross primary production) during the preceding months and a potential reduction in biomass (≤8.3%) due to repeat fires.
Deeter, M. N., D. P. Edwards, J. C. Gille, and H. M. Worden (2015), Information content of MOPITT CO profile retrievals: Temporal and geographical variability, J. Geophys. Res.-Atmos., 120(24), 12723–12738, doi:10.1002/2015JD024024.
Satellite measurements of tropospheric carbon monoxide (CO) enable a wide array of applications including studies of air quality and pollution transport. The MOPITT (Measurements of Pollution in the Troposphere) instrument on the Earth Observing System Terra platform has been measuring CO concentrations globally since March 2000. As indicated by the Degrees of Freedom for Signal (DFS), the standard metric for trace-gas retrieval information content, MOPITT retrieval performance varies over a wide range. We show that both instrumental and geophysical effects yield significant geographical and temporal variability in MOPITT DFS values. Instrumental radiance uncertainties, which describe random errors (or “noise”) in the calibrated radiances, vary over long time scales (e.g., months to years) and vary between the four detector elements of MOPITT’s linear detector array. MOPITT retrieval performance depends on several factors including thermal contrast, fine-scale variability of surface properties, and CO loading. The relative importance of these various effects is highly variable, as demonstrated by analyses of monthly mean DFS values for the United States and the Amazon Basin. An understanding of the geographical and temporal variability of MOPITT retrieval performance is potentially valuable to data users seeking to limit the influence of the a priori through data filtering. To illustrate, it is demonstrated that calculated regional-average CO mixing ratios may be improved by excluding observations from a subset of pixels in MOPITT’s linear detector array.
Jena, C., S. D. Ghude, G. G. Pfister, D. M. Chate, R. Kumar, G. Beig, D. E. Surendran, S. Fadnavis, and D. M. Lal (2015), Influence of springtime biomass burning in South Asia on regional ozone (O3): A model based case study, Atmospheric Environment, 100, 37–47, doi:10.1016/j.atmosenv.2014.10.027.
In this study, for the first time, the influence of springtime (MAM) biomass burning in South Asia on regional ozone (O3) distribution has been evaluated using a regional chemical transport model (WRF-Chem) and the Fire Inventory from NCAR (FINNv1). Model results are compared with satellite retrievals of tropospheric column amounts of carbon monoxide (CO) from MOPITT and nitrogen dioxide (NO2) from OMI. With daily varying emissions, the model captures reasonably well the satellite-derived temporal variations in CO and NO2 (index of agreement (R) for CO is 0.83 and for NO2 is 0.76), indicating the effectiveness of the model in estimating the overall fire impact on a regional scale. Simulated tropospheric NO2 concentration shows better agreement with the magnitude of observed NO2 when FINNv1 NOx emissions are reduced by a factor of 2.2 over the model domain. A clear increase in CO and NO2 levels over Burma (35–60%), Central India (15–30%), the Indo-Gangetic (15–25%) region and the Bay of Bengal (15–40%) are simulated with fire emissions. The model results are also used to quantify the net O3 production from fires. Calculated O3 productions are up to 4 ppb h−1 over inland and up to 0.1 ppb h−1 over marine regions respectively. Our model-based analysis yields average enhancement ratios ΔO3/ΔCO of 0.12 ppbv/ppbv and a total O3 production of about 3.5 Tg from South Asia during the spring season. The findings demonstrate that the springtime fire emissions in South Asia have a noticeable impact on the O3 in this region.
Jiang, Z., D. B. A. Jones, J. Worden, H. M. Worden, D. K. Henze, and Y. X. Wang (2015a), Regional data assimilation of multi-spectral MOPITT observations of CO over North America, Atmos. Chem. Phys., 15(12), 6801–6814, doi:10.5194/acp-15-6801-2015.
Chemical transport models (CTMs) driven with high-resolution meteorological fields can better resolve small-scale processes, such as frontal lifting or deep convection, and thus improve the simulation and emission estimates of tropospheric trace gases. In this work, we explore the use of the GEOS-Chem four-dimensional variational (4D-Var) data assimilation system with the nested high-resolution version of the model (0.5A degrees x 0.67A degrees) to quantify North American CO emissions during the period of June 2004-May 2005. With optimized lateral boundary conditions, regional inversion analyses can reduce the sensitivity of the CO source estimates to errors in long-range transport and in the distributions of the hydroxyl radical (OH), the main sink for CO. To further limit the potential impact of discrepancies in chemical aging of air in the free troposphere, associated with errors in OH, we use surface-level multispectral MOPITT (Measurement of Pollution in The Troposphere) CO retrievals, which have greater sensitivity to CO near the surface and reduced sensitivity in the free troposphere, compared to previous versions of the retrievals. We estimate that the annual total anthropogenic CO emission from the contiguous US 48 states was 97 Tg CO, a 14 % increase from the 85 Tg CO in the a priori. This increase is mainly due to enhanced emissions around the Great Lakes region and along the west coast, relative to the a priori. Sensitivity analyses using different OH fields and lateral boundary conditions suggest a possible error, associated with local North American OH distribution, in these emission estimates of 20 % during summer 2004, when the CO lifetime is short. This 20 % OH-related error is 50 % smaller than the OH-related error previously estimated for North American CO emissions using a global inversion analysis. We believe that reducing this OH-related error further will require integrating additional observations to provide a strong constraint on the CO distribution across the domain. Despite these limitations, our results show the potential advantages of combining high-resolution regional inversion analyses with global analyses to better quantify regional CO source estimates.
Jiang, Z., D. B. A. Jones, H. M. Worden, and D. K. Henze (2015b), Sensitivity of top-down CO source estimates to the modeled vertical structure in atmospheric CO, Atmos. Chem. Phys., 15(3), 1521–1537, doi:10.5194/acp-15-1521-2015.
We assessed the sensitivity of regional CO source estimates to the modeled vertical CO distribution by assimilating multi-spectral MOPITT (Measurements of Pollution In The Troposphere) V5J CO retrievals with the GEOS-Chem model. We compared the source estimates obtained by assimilating the CO profiles and the surface layer retrievals from June 2004 to May 2005. Because the surface layer retrievals are less sensitive to CO in the free troposphere, it is expected that they should provide constraints in the CO source estimates that are less sensitive to the vertical structure of CO in the free troposphere. The inferred source estimates all suggest a reduction in CO emissions in the tropics and subtropics, and an increase in the extratropics over the a priori estimates. The tropical decreases were particularly pronounced for regions where the biogenic source of CO was dominant, suggesting an overestimate of the a priori isoprene source of CO in the model. We found that the differences between the regional source estimates inferred from the profile and surface layer retrievals for 2004–2005 were small, generally less than 10% for the main continental regions, except for estimates for southern Asia, North America, and Europe. Because of discrepancies in convective transport in the model, the CO source estimates for India and southeastern Asia inferred from the CO profiles were significantly higher than those estimated from the surface layer retrievals during June–August 2004. On the other hand, the profile inversion underestimated the CO emissions from North America and Europe compared to the assimilation of the surface layer retrievals. We showed that vertical transport of air from the North American and European boundary layers is slower than from other continental regions, and thus air in the free troposphere from North America and Europe in the model is more chemically aged, which could explain the discrepancy between the source estimates inferred from the profile and surface layer retrievals. We also examined the impact of the OH distribution on the source estimates and found that the discrepancies between the source estimates obtained with two OH fields were larger when using the profile data, which is consistent with greater sensitivity to the more chemically aged air in the free troposphere. Our findings indicate that regional CO source estimates are sensitive to the vertical CO structure. They suggest that diagnostics to assess the age of air from the continental source regions should help interpret the results from CO source inversions. Our results also suggest that assimilating a broader range of composition measurements to provide better constraint on tropospheric OH and the biogenic sources of CO is essential for reliable quantification of the regional CO budget.
Marey, H. S., Z. Hashisho, L. Fu, and J. Gille (2015), Spatial and temporal variation in CO over Alberta using measurements from satellites, aircraft, and ground stations, Atmos. Chem. Phys., 15(7), 3893–3908, doi:10.5194/acp-15-3893-2015.
Alberta is Canada’s largest oil producer, and its oil sands deposits comprise 30% of the world’s oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO) levels over Alberta. The multispectral product that uses both near-infrared (NIR) and the thermal-infrared (TIR) radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT) is examined for the 12-year period from 2002 to 2013. The Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations in forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System) aircraft CO profiles (April 2009-December 2011) are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons: summer and spring. Distinct seasonal patterns of CO at the urban sites (Edmonton and Calgary) point to the strong influence of traffic. Meteorological parameters play an important role in the CO spatial distribution at various pressure levels. Northern Alberta shows a stronger upward lifting motion which leads to larger CO total column values, while the poor dispersion in central and southern Alberta exacerbates the surface CO pollution. Interannual variations in satellite data depict a slightly decreasing trend for both regions, while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO vertical averages and MOZAIC/IAGOS aircraft profiles were in good agreement within the standard deviations at all pressure levels. There is consistency between the time evolution of high-CO episodes monitored by satellite and ground measurements and the fire frequency peak time, which implies that biomass burning has affected the tropospheric CO distribution in northern Alberta. These findings have further demonstrated the potential use of the MOPITT V5 multispectral (NIR + TIR) product for assessing a complicated surface process.
Surendran, D. E., S. D. Ghude, G. Beig, L. K. Emmons, C. Jena, R. Kumar, G. G. Pfister, and D. M. Chate (2015), Air quality simulation over South Asia using Hemispheric Transport of Air Pollution version-2 (HTAP-v2) emission inventory and Model for Ozone and Related chemical Tracers (MOZART-4), Atmos. Environ., 122, 357–372, doi:10.1016/j.atmosenv.2015.08.023.
This study presents the distribution of tropospheric ozone and related species for South Asia using the Model for Ozone and Related chemical Tracers (MOZART-4) and Hemispheric Transport of Air Pollution version-2 (HTAP-v2) emission inventory. The model present-day simulated ozone (O-3), carbon monoxide (CO) and nitrogen dioxide (NO2) are evaluated against surface-based, balloon-borne and satellite-based (MOPITT and OMI) observations. The model systematically overestimates surface O-3 mixing ratios (range of mean bias about: 1-30 ppbv) at different ground-based measurement sites in India. Comparison between simulated and observed vertical profiles of ozone shows a positive bias from the surface up to 600 hPa and a negative bias above 600 hPa. The simulated seasonal variation in surface CO mixing ratio is consistent with the surface observations, but has a negative bias of about 50-200 ppb which can be attributed to a large part to the coarse model resolution. In contrast to the surface evaluation, the model shows a positive bias of about 15-20 x 10(17) molecules/cm(2) over South Asia when compared to satellite derived CO columns from the MOPITT instrument. The model also overestimates OMI retrieved tropospheric column NO2 abundance by about 100-250 x 10(13) molecules/cm(2). A response to 20% reduction in all anthropogenic emissions over South Asia shows a decrease in the anuual mean O-3 mixing ratios by about 3-12 ppb, CO by about 10-80 ppb and NOx by about 3-6 ppb at the surface level. During summer monsoon, O-3 mixing ratios at 200 hPa show a decrease of about 6-12 ppb over South Asia and about 1-4 ppb over the remote northern hemispheric western Pacific region. (C) 2015 Elsevier Ltd. All rights reserved.
Wang, K., K. Yahya, Y. Zhang, C. Hogrefe, G. Pouliot, C. Knote, A. Hodzic, R. San Jose, J. L. Perez, P. Jiménez-Guerrero, R. Baro, P. Makar, and R. Bennartz (2015), A multi-model assessment for the 2006 and 2010 simulations under the Air Quality Model Evaluation International Initiative (AQMEII) Phase 2 over North America: Part II. Evaluation of column variable predictions using satellite data, Atmospheric Environment, doi:10.1016/j.atmosenv.2014.07.044. [online] Available from: .
Within the context of the Air Quality Model Evaluation International Initiative Phase 2 (AQMEII2) project, this part II paper performs a multi-model assessment of major column abundances of gases, radiation, aerosol, and cloud variables for 2006 and 2010 simulations with three online-coupled air quality models over the North America using available satellite data. It also provides the first comparative assessment of the capabilities of the current generation of online-coupled models in simulating column variables. Despite the use of different model configurations and meteorological initial and boundary conditions, most simulations show comparable model performance for many variables. The evaluation results show an excellent agreement between all simulations and satellite-derived radiation variables including downward surface solar radiation, longwave radiation, and top-of-atmospheric outgoing longwave radiation, as well as precipitable water vapor with domain-average normalized mean biases (NMBs) of typically less than 5% and correlation coefficient (R) typically more than 0.9. Most simulations perform well for column-integrated abundance of CO with domain-average NMBs of −9.4% to −2.2% in 2006 and −12.1% to 4.6% in 2010 and from reasonably well to fair for column NO2, HCHO, and SO2, with domain-average NMBs of −37.7% to 2.1%, −27.3% to 59.2%, and 16.1% to 114.2% in 2006, respectively, and, 12.9% to 102.1%, −25.0% to 87.6%, −65.2% to 7.4% in 2010, respectively. R values are high for CO and NO2 typically between 0.85 and 0.9 (i.e., R2 of 0.7–0.8). Tropospheric ozone residuals are overpredicted by all simulations due to overestimates of ozone profiles from boundary conditions. Model performance for cloud-related variables is mixed and generally worse compared to gases and radiation variables. Cloud fraction (CF) is well reproduced by most simulations. Other aerosol/cloud related variables such as aerosol optical depth (AOD), cloud optical thickness, cloud liquid water path, cloud condensation nuclei, and cloud droplet number concentration (CDNC) are moderately to largely underpredicted by most simulations, due to underpredictions of aerosol loadings and also indicating high uncertainties associated with the current model treatments of aerosol–cloud interactions and the need for further model development. Negative correlations are found for AOD for most simulations due to large negative biases over the western part of the domain. Inter-model discrepancies also exist for a few variables such as column abundances of HCHO and SO2 and CDNC due likely to different chemical mechanisms, biogenic emissions, and treatments of aerosol indirect effects. Most simulations can also capture the inter-annual trend observed by satellites between 2006 and 2010 for several variables such as column abundance of NO2, AOD, CF, and CDNC. Results shown in this work provide the important benchmark for future online-couple air quality model development.
Zeng, G., J. E. Williams, J. A. Fisher, L. K. Emmons, N. B. Jones, O. Morgenstern, J. Robinson, D. Smale, C. Paton-Walsh, and D. W. T. Griffith (2015), Multi-model simulation of CO and HCHO in the Southern Hemisphere: comparison with observations and impact of biogenic emissions, Atmospheric Chemistry and Physics, 15(13), 7217–7245, doi:
We investigate the impact of biogenic emissions on carbon monoxide (CO) and formaldehyde (HCHO) in the Southern Hemisphere (SH), with simulations using two different biogenic emission inventories for isoprene and monoterpenes. Results from four atmospheric chemistry models are compared to continuous long-term ground-based CO and HCHO column measurements at the SH Network for the Detection of Atmospheric Composition Change (NDACC) sites, the satellite measurement of tropospheric CO columns from the Measurement of Pollution in the Troposphere (MOPITT), and in situ surface CO measurements from across the SH, representing a subset of the National Oceanic and Atmospheric Administration’s Global Monitoring Division (NOAA GMD) network. Simulated mean model CO using the Model of Emissions of Gases and Aerosols from Nature (v2.1) computed in the frame work of the Land Community Model (CLM-MEGANv2.1) inventory is in better agreement with both column and surface observations than simulations adopting the emission inventory generated from the LPJ-GUESS dynamical vegetation model framework, which markedly underestimate measured column and surface CO at most sites. Differences in biogenic emissions cause large differences in CO in the source regions which propagate to the remote SH. Significant inter-model differences exist in modelled column and surface CO, and secondary production of CO dominates these inter-model differences, due mainly to differences in the models’ oxidation schemes for volatile organic compounds, predominantly isoprene oxidation. While biogenic emissions are a significant factor in modelling SH CO, inter-model differences pose an additional challenge to constrain these emissions. Corresponding comparisons of HCHO columns at two SH mid-latitude sites reveal that all models significantly underestimate the observed values by approximately a factor of 2. There is a much smaller impact on HCHO of the significantly different biogenic emissions in remote regions, compared to the source regions. Decreased biogenic emissions cause decreased CO export to remote regions, which leads to increased OH; this in turn results in increased HCHO production through methane oxidation. In agreement with earlier studies, we corroborate that significant HCHO sources are likely missing in the models in the remote SH.


Amnuaylojaroen, T., M. C. Barth, L. K. Emmons, G. R. Carmichael, J. Kreasuwun, S. Prasitwattanaseree, and S. Chantara (2014), Effect of different emission inventories on modeled ozone and carbon monoxide in Southeast Asia, Atmospheric Chemistry and Physics, 14(23), 12983–13012, doi:10.5194/acp-14-12983-2014.
In order to improve our understanding of air quality in Southeast Asia, the anthropogenic emissions inventory must be well represented. In this work, we apply different anthropogenic emission inventories in the Weather Research and Forecasting Model with Chemistry (WRF-Chem) version 3.3 using Model for Ozone and Related Chemical Tracers (MOZART) gas-phase chemistry and Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) aerosols to examine the differences in predicted carbon monoxide (CO) and ozone (O3) surface mixing ratios for Southeast Asia in March and December 2008. The anthropogenic emission inventories include the Reanalysis of the TROpospheric chemical composition (RETRO), the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B), the MACCity emissions (adapted from the Monitoring Atmospheric Composition and Climate and megacity Zoom for the Environment projects), the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS) emissions, and a combination of MACCity and SEAC4RS emissions. Biomass-burning emissions are from the Fire Inventory from the National Center for Atmospheric Research (NCAR) (FINNv1) model. WRF-Chem reasonably predicts the 2 m temperature, 10 m wind, and precipitation. In general, surface CO is underpredicted by WRF-Chem while surface O3 is overpredicted. The NO2 tropospheric column predicted by WRF-Chem has the same magnitude as observations, but tends to underpredict the NO2 column over the equatorial ocean and near Indonesia. Simulations using different anthropogenic emissions produce only a slight variability of O3 and CO mixing ratios, while biomass-burning emissions add more variability. The different anthropogenic emissions differ by up to 30 % in CO emissions, but O3 and CO mixing ratios averaged over the land areas of the model domain differ by ∼ 4.5 % and ∼ 8 %, respectively, among the simulations. Biomass-burning emissions create a substantial increase for both O3 and CO by ∼ 29 % and ∼ 16 %, respectively, when comparing the March biomass-burning period to the December period with low biomass-burning emissions. The simulations show that none of the anthropogenic emission inventories are better than the others for predicting O3 surface mixing ratios. However, the simulations with different anthropogenic emission inventories do differ in their predictions of CO surface mixing ratios producing variations of ∼ 30 % for March and 10–20 % for December at Thai surface monitoring sites.
Anderson, D. C., C. P. Loughner, G. Diskin, A. Weinheimer, T. P. Canty, R. J. Salawitch, H. M. Worden, A. Fried, T. Mikoviny, A. Wisthaler, and R. R. Dickerson (2014), Measured and modeled CO and NOy in DISCOVER-AQ: An evaluation of emissions and chemistry over the eastern US, Atmospheric Environment, 96, 78–87, doi:10.1016/j.atmosenv.2014.07.004.
Data collected during the 2011 DISCOVER-AQ field campaign in the Baltimore Washington region were used to evaluate CO and NOx emissions in the National Emissions Inventory (NEI). The average emissions ratio for the region was seen to be 11.2 ± 1.2 mol CO/mol NOx, 21% higher than that predicted by the NEI. Comparisons between in situ and remote observations and CMAQ model output show agreement in CO emissions of 15 ± 11% while NOx emissions are overestimated by 51–70% in Maryland. Satellite observations of CO by MOPITT show agreement with the Community Multiscale Air Quality (CMAQ) model within 3% over most of the eastern United States. CMAQ NOy mixing ratios were a factor of two higher than observations and result from a combination of errors in emissions and PAN and alkyl nitrate chemistry, as shown by comparison of three CMAQ model runs. Point source NOx emissions are monitored and agree with modeled emissions within 1% on a monthly basis. Because of this accuracy and the NEI assertion that approximately 3/4 of emissions in the Baltimore Washington region are from mobile sources, the MOVES model’s treatment of emissions from aging vehicles should be investigated; the NEI overestimate of NOx emissions could indicate that engines produce less NOx and catalytic converters degrade more slowly than assumed by MOVES2010. The recently released 2011 NEI has an even lower CO/NOx emissions ratio than the projection used in this study; it overestimates NOx emissions by an even larger margin. The implications of these findings for US air quality policy are that NOx concentrations near areas of heavy traffic are overestimated and ozone production rates in these locations are slower than models indicate. Results also indicate that ambient ozone concentrations will respond more efficiently to NOx emissions controls but additional sources may need to be targeted for reductions.
Deeter, M. N., S. Martínez-Alonso, D. P. Edwards, L. K. Emmons, J. C. Gille, H. M. Worden, C. Sweeney, J. V. Pittman, B. C. Daube, and S. C. Wofsy (2014), The MOPITT Version 6 product: algorithm enhancements and validation, Atmos. Meas. Tech., 7(11), 3623–3632, doi:10.5194/amt-7-3623-2014.
The Measurements of Pollution in the Troposphere (MOPITT) Version 6 (V6) product for carbon monoxide (CO) incorporates several enhancements which will benefit many users of MOPITT data. V6 algorithm improvements are described in detail, and V6 validation results are presented. First, a geolocation bias related to the orientation of the MOPITT instrument relative to the TERRA platform was characterized and eliminated. Second, the variable a priori for CO concentrations for V6 is based on simulations performed with the chemical transport model Community Atmosphere Model with Chemistry (CAM-chem) for the years 2000–2009 instead of the model-derived climatology for 1997–2004 used for V5. Third, meteorological fields required for V6 retrieval processing are extracted from the MERRA (Modern-Era Retrospective Analysis For Research And Applications) reanalysis. Finally, a significant latitude-dependent retrieval bias in the upper troposphere in Version 5 products has been substantially reduced.
Duncan, B. N., A. I. Prados, L. N. Lamsal, Y. Liu, D. G. Streets, P. Gupta, E. Hilsenrath, R. A. Kahn, J. E. Nielsen, A. J. Beyersdorf, S. P. Burton, A. M. Fiore, J. Fishman, D. K. Henze, C. A. Hostetler, N. A. Krotkov, P. Lee, M. Lin, S. Pawson, G. Pfister, K. E. Pickering, R. B. Pierce, Y. Yoshida, and L. D. Ziemba (2014), Satellite data of atmospheric pollution for U.S. air quality applications: Examples of applications, summary of data end-user resources, answers to FAQs, and common mistakes to avoid, Atmospheric Environment, 94, 647–662, doi:10.1016/j.atmosenv.2014.05.061.
Satellite data of atmospheric pollutants are becoming more widely used in the decision-making and environmental management activities of public, private sector and non-profit organizations. They are employed for estimating emissions, tracking pollutant plumes, supporting air quality forecasting activities, providing evidence for “exceptional event” declarations, monitoring regional long-term trends, and evaluating air quality model output. However, many air quality managers are not taking full advantage of the data for these applications nor has the full potential of satellite data for air quality applications been realized. A key barrier is the inherent difficulties associated with accessing, processing, and properly interpreting observational data. A degree of technical skill is required on the part of the data end-user, which is often problematic for air quality agencies with limited resources. Therefore, we 1) review the primary uses of satellite data for air quality applications, 2) provide some background information on satellite capabilities for measuring pollutants, 3) discuss the many resources available to the end-user for accessing, processing, and visualizing the data, and 4) provide answers to common questions in plain language.
El Amraoui, L., J.-L. Attie, P. Ricaud, W. A. Lahoz, A. Piacentini, V.-H. Peuch, J. X. Warner, R. Abida, J. Barre, and R. Zbinden (2014), Tropospheric CO vertical profiles deduced from total columns using data assimilation: methodology and validation, Atmos. Meas. Tech., 7(9), 3035–3057, doi:10.5194/amt-7-3035-2014.
This paper presents a validation of a method to derive the vertical profile of carbon monoxide (CO) from its total column using data assimilation. We choose version 3 of MOPITT CO total columns to validate the proposed method. MOPITT products have the advantage of providing both the vertical profiles and the total columns of CO. Furthermore, this version has been extensively validated by comparison with many independent data sets, and has been used in many scientific studies. The first step of the paper consists in the specification of the observation errors based on the chi-square (chi(2)) test. The observations have been binned according to three types: over land during daytime, over land during night-time, and over sea. Their respective errors using the chi(2) metric have been found to be 8, 11 and 7 %. In the second step, the CO total columns, with their specified errors, are used within the assimilation system to estimate the vertical profiles. These are compared to the retrieved profiles of MOPITT V3 at global and regional scales. Generally, the two data sets show similar patterns and good agreement at both scales. Nevertheless, total column analyses slightly overestimate CO concentrations compared to MOPITT observations. The mean bias between both data sets is +15 and +12% at 700 and 250 hPa, respectively. In the third step, the assimilation of total column has been compared to the assimilation of MOPITT vertical profiles. The differences between both analyses are very small. In terms longitude-latitude maps, the mean bias between the two data sets is +6 and +8% at the pressure levels 700 and 200 hPa, respectively. In terms of zonal means, the CO distribution is similar for both analyses, with a mean bias which does not exceed 12 %. Finally, the two analyses have been validated using independent observations from the aircraft-based MOZAIC program in terms of vertical profiles over eight airports. Over most airports, both analyses agree well with aircraft profiles. For more than 50% of recorded measurements, the difference between the analyses and MOZAIC does not exceed 5 ppbv (parts per billion by volume).
Gonzi, S., P. I. Palmer, R. Paugam, M. Wooster, and M. N. Deeter (2014), Quantifying pyroconvective injection heights using observations of fire  energy: sensitivity of space-borne observations of carbon monoxide, Atmos. Chem. Phys. Discuss., 14(16), 22547–22585, doi:10.5194/acpd-14-22547-2014.
We use observations of fire size and fire radiative power (FRP) from the NASA Moderate-Resolution Imaging Spectroradiometers (MODIS), together with a parameterized plume rise model, to estimate biomass burning injection heights during 2006.  We use these injection heights in the GEOS-Chem atmospheric chemistry transport  model to  vertically distribute biomass burning emissions of carbon monoxide (CO) and to study the resulting atmospheric distribution. For 2006, we use over half a million FRP and fire size observations as input to the plume rise model.  We find that convective heat fluxes and actual fire sizes typically lie in the range of 1–100 kW m−2 and 0.001–100 ha, respectively, although in rare circumstances the convective heat flux can exceed 500 kW m−2.  The resulting injection heights have a skewed probability distribution  with approximately 80% of injections remaining within the local boundary layer (BL), with occasional injection height exceeding 8 km. We do not find a strong correlation between the FRP-inferred surface convective heat flux and the  resulting injection height, with environmental conditions often acting as a barrier to rapid vertical mixing even where the convective heat flux and  actual fire size are large. We also do not find a robust relationship between the underlying burnt vegetation type and the injection height. We find that CO columns calculated using the MODIS-inferred injection height (MODIS-inj) are typically  −9–+6% different to the control calculation in which emissions are emitted into the BL, with differences typically largest over the point of emission. After applying MOPITT v5 scene-dependent averaging kernels we find that we are much less sensitive to our choice of injection height profile.  The differences between the MOPITT and the model CO columns (max bias ≈ 50%), due largely to uncertainties in emission inventories, are much larger than those introduced by the injection heights. We show that including a realistic diurnal variation in FRP (peaking in the afternoon) or accounting for subgrid-scale emission errors does not alter our main conclusions. Finally, we use a Bayesian maximum a posteriori approach constrained by MOPITT CO profiles to estimate the CO emissions but because of the inherent bias between model and MOPITT  we find little impact on the resulting emission estimates. Studying the role of pyroconvection in distributing gases and particles in the atmosphere using global MOPITT CO observations (or any current space-borne measurement of the atmosphere) is still associated with large errors,  with the exception of a small subset of large fires and favourable environmental conditions, which will consequently lead to a bias in any analysis on a global scale.
de Laat, A. T. J., I. Aben, M. Deeter, P. Nédélec, H. Eskes, J.-L. Attié, P. Ricaud, R. Abida, L. El Amraoui, and J. Landgraf (2014), Validation of nine years of MOPITT V5 NIR using MOZAIC/IAGOS measurements: biases and long-term stability, Atmos. Meas. Tech., 7(11), 3783–3799, doi:10.5194/amt-7-3783-2014.
Validation results from a comparison between Measurement Of Pollution In The Troposphere (MOPITT) V5 Near InfraRed (NIR) carbon monoxide (CO) total column measurements and Measurement of Ozone and Water Vapour on Airbus in-service Aircraft (MOZAIC)/In-Service Aircraft for a Global Observing System (IAGOS) aircraft measurements are presented. A good agreement is found between MOPITT and MOZAIC/IAGOS measurements, consistent with results from earlier studies using different validation data and despite large variability in MOPITT CO total columns along the spatial footprint of the MOZAIC/IAGOS measurements. Validation results improve when taking the large spatial footprint of the MOZAIC/IAGOS data into account. No statistically significant drift was detected in the validation results over the period 2002–2010 at global, continental and local (airport) scales. Furthermore, for those situations where MOZAIC/IAGOS measurements differed from the MOPITT a priori, the MOPITT measurements clearly outperformed the MOPITT a priori data, indicating that MOPITT NIR retrievals add value to the MOPITT a priori. Results from a high spatial resolution simulation of the chemistry-transport model MOCAGE (MOdèle de Chimie Atmosphérique à Grande Echelle) showed that the most likely explanation for the large MOPITT variability along the MOZAIC-IAGOS profile flight path is related to spatio-temporal CO variability, which should be kept in mind when using MOZAIC/IAGOS profile measurements for validating satellite nadir observations.
Martínez-Alonso, S., M. N. Deeter, H. M. Worden, J. C. Gille, L. K. Emmons, L. L. Pan, M. Park, G. L. Manney, P. F. Bernath, C. D. Boone, K. A. Walker, F. Kolonjari, S. C. Wofsy, J. Pittman, and B. C. Daube (2014), Comparison of Upper Tropospheric Carbon Monoxide from MOPITT, ACE-FTS, and HIPPO-QCLS, J. Geophys. Res. Atmos., 2014JD022397, doi:10.1002/2014JD022397.
Products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument are regularly validated using in situ airborne measurements. However, few of these measurements reach into the upper troposphere, thus hindering MOPITT validation in that region. Here we evaluate upper tropospheric (~500 hPa to the tropopause) MOPITT CO profiles by comparing them to satellite Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) retrievals and to measurements from the High-performance Instrumented Airborne Platform for Environmental Research Pole to Pole Observations (HIPPO) Quantum Cascade Laser Spectrometer (QCLS). Direct comparison of co-located v5 MOPITT thermal-infrared-only retrievals, v3.0 ACE-FTS retrievals, and HIPPO-QCLS measurements show a slight positive MOPITT CO bias within its 10% accuracy requirement with respect to the other two datasets. Direct comparison of co-located ACE-FTS and HIPPO-QCLS measurements results in a small number of samples, due to the large disparity in sampling pattern and density of these datasets. Thus, two additional indirect techniques for comparison of non-coincident datasets have been applied: tracer-tracer (CO-O3) correlation analysis and analysis of profiles in tropopause coordinates. These techniques suggest a negative bias of ACE-FTS with respect to HIPPO-QCLS; this could be caused by differences in resolution (horizontal, vertical) or by deficiencies in the ACE-FTS CO retrievals below ~20 km of altitude, among others. We also investigate the temporal stability of MOPITT and ACE-FTS data, which provide unique global CO records and are thus important in climate analysis. Our results indicate that the relative bias between the two datasets has remained generally stable during the 2004–2010 period.
Worden, H. M., M. N. Deeter, D. P. Edwards, J. Gille, J. Drummond, L. K. Emmons, G. Francis, and S. Martínez-Alonso (2014), 13 years of MOPITT operations: lessons from MOPITT retrieval algorithm development, Ann. Geophys., 56(0), doi:10.4401/ag-6330. [online] Available from:
The Measurements of Pollution in the Troposphere (MOPITT) instrument on the NASA Terra platform has now acquired over thirteen years of global tropospheric carbon monoxide (CO) observations, forming the longest satellite record for an important pollutant. MOPITT products are routinely exploited for characterizing CO sources and for analyzing air quality. For retrieving CO concentrations in the lower troposphere, MOPITT is equipped with both thermal-infrared and near-infrared channels.
Zoogman, P., D. J. Jacob, K. Chance, H. M. Worden, D. P. Edwards, and L. Zhang (2014), Improved monitoring of surface ozone by joint assimilation of geostationary satellite observations of ozone and CO, Atmospheric Environment, 84, 254–261, doi:10.1016/j.atmosenv.2013.11.048.
Future geostationary satellite observations of tropospheric ozone aim to improve monitoring of surface ozone air quality. However, ozone retrievals from space have limited sensitivity in the lower troposphere (boundary layer). Data assimilation in a chemical transport model can propagate the information from the satellite observations to provide useful constraints on surface ozone. This may be aided by correlated satellite observations of carbon monoxide (CO), for which boundary layer sensitivity is easier to achieve. We examine the potential of concurrent geostationary observations of ozone and CO to improve constraints on surface ozone air quality through exploitation of ozone–CO model error correlations in a joint data assimilation framework. The hypothesis is that model transport errors diagnosed for CO provide information on corresponding errors in ozone. A paired-model analysis of ozone–CO error correlations in the boundary layer over North America in summer indicates positive error correlations in continental outflow but negative regional-scale error correlations over land, the latter reflecting opposite sensitivities of ozone and CO to boundary layer depth. Aircraft observations from the ICARTT campaign are consistent with this pattern but also indicate strong positive error correlations in fine-scale pollution plumes. We develop a joint ozone–CO data assimilation system and apply it to a regional-scale Observing System Simulation Experiment (OSSE) of the planned NASA GEO-CAPE geostationary mission over North America. We find substantial benefit from joint ozone–CO data assimilation in informing US ozone air quality if the instrument sensitivity for CO in the boundary layer is greater than that for ozone. A high-quality geostationary measurement of CO could potentially relax the requirements for boundary layer sensitivity of the ozone measurement. This is contingent on accurate characterization of ozone–CO error correlations. A finer-resolution data assimilation system resolving the urban scale would need to account for the change in sign of the ozone–CO error correlations between urban pollution plumes and the regional atmosphere.


Barré, J., L. El Amraoui, P. Ricaud, W. A. Lahoz, J.-L. Attié, V.-H. Peuch, B. Josse, and V. Marécal (2013), Diagnosing the transition layer at extratropical latitudes using MLS O3 and MOPITT CO analyses, Atmos. Chem. Phys., 13(14), 7225–7240, doi:10.5194/acp-13-7225-2013.
The behavior of the extratropical transition layer (ExTL) is investigated using a chemistry transport model (CTM) and analyses derived from assimilation of MLS (Microwave Limb Sounder) O-3 and MOPITT (Measurements Of Pollution In The Troposphere) CO data. We firstly focus on a stratosphere-troposphere exchange (STE) case study that occurred on 15 August 2007 over the British Isles (50 degrees N, 10 degrees W). We evaluate the effect of data assimilation on the O-3-CO correlations. It is shown that data assimilation disrupts the relationship in the transition region. When MLS O-3 is assimilated, CO and O-3 values are not consistent between each other, leading to unphysical correlations at the STE location. When MLS O-3 and MOPITT CO assimilated fields are taken into account in the diagnostics the relationship happens to be more physical. We then use O-3-CO correlations to quantify the effect of data assimilation on the height and depth of the ExTL. When the free-model run O-3 and CO fields are used in the diagnostics, the ExTL distribution is found 1.1 km above the thermal tropopause and is 2.6 km wide (2 sigma). MOPITT CO analyses only slightly sharpen (by -0.02 km) and lower (by -0.2 km) the ExTL distribution. MLS O-3 analyses provide an expansion (by +0.9 km) of the ExTL distribution, suggesting a more intense O-3 mixing. However, the MLS O-3 analyses ExTL distribution shows a maximum close to the thermal tropopause and a mean location closer to the thermal tropopause (+0.45 km). When MLS O-3 and MOPITT CO analyses are used together, the ExTL shows a mean location that is the closest to the thermal tropopause (+0.16 km). We also extend the study at the global scale on 15 August 2007 and for the month of August 2007. MOPITT CO analyses still show a narrower chemical transition between stratosphere and troposphere than the free-model run. MLS O-3 analyses move the ExTL toward the troposphere and broaden it. When MLS O-3 analyses and MOPITT CO analyses are used together, the ExTL matches the thermal tropopause poleward of 50 degrees.
Deeter, M. N., S. Martínez-Alonso, D. P. Edwards, L. K. Emmons, J. C. Gille, H. M. Worden, J. V. Pittman, B. C. Daube, and S. C. Wofsy (2013), Validation of MOPITT Version 5 thermal-infrared, near-infrared, and multispectral carbon monoxide profile retrievals for 2000–2011, Journal of Geophysical Research: Atmospheres, n/a–n/a, doi:10.1002/jgrd.50272.
Validation results are reported for the MOPITT (Measurements of Pollution in the Troposphere) “Version 5” (V5) product for tropospheric carbon monoxide (CO) and are compared to results for the “Version 4” product. The V5 retrieval algorithm introduces (1) a method for reducing retrieval bias drift associated with long-term instrumental degradation, (2) a more exact representation of the effects of random errors in the radiances and, for the first time, (3) the use of MOPITT’s near-infrared (NIR) radiances to complement the thermal-infrared (TIR) radiances. Exploiting TIR and NIR radiances together facilitates retrievals of CO in the lowermost troposphere. V5 retrieval products based (1) solely on TIR measurements, (2) solely on NIR measurements and (3) on both TIR and NIR measurements are separately validated and analyzed. Actual retrieved CO profiles and total columns are compared with equivalent retrievals based on in situ measurements from (1) routine NOAA aircraft sampling mainly over North America and (2) the “HIAPER Pole to Pole Observations” (HIPPO) field campaign. Particular attention is focused on the long-term stability and geographical uniformity of the retrieval errors. Results for the retrieved total column clearly indicate reduced temporal bias drift in the V5 products compared to the V4 product, and do not exhibit a positive bias in the Southern Hemisphere, which is evident in the V4 product.
He, H., J. W. Stehr, J. C. Hains, D. J. Krask, B. G. Doddridge, K. Y. Vinnikov, T. P. Canty, K. M. Hosley, R. J. Salawitch, H. M. Worden, and R. R. Dickerson (2013), Trends in emissions and concentrations of air pollutants in the lower troposphere in the Baltimore/Washington airshed from 1997 to 2011, Atmos. Chem. Phys., 13(15), 7859–7874, doi:10.5194/acp-13-7859-2013.
Trends in the composition of the lower atmosphere (0–1500 m altitude) and surface air quality over the Baltimore/Washington area and surrounding states were investigated for the period from 1997 to 2011. We examined emissions of ozone precursors from monitors and inventories as well as ambient ground-level and aircraft measurements to characterize trends in air pollution. The US EPA Continuous Emissions Monitoring System (CEMS) program reported substantial decreases in emission of summertime nitrogen oxides (NOx) from power plants, up to ∼80% in the mid-Atlantic States. These large reductions in emission of NOx are reflected in a sharp decrease of ground-level concentrations of NOx starting around 2003. The decreasing trend of tropospheric column CO observed by aircraft is ∼0.8 Dobson unit (DU) per year, corresponding to ∼35 ppbv yr−1 in the lower troposphere (the surface to 1500 m above ground level). Satellite observations of long-term, near-surface CO show a ∼40% decrease over western Maryland between 2000 and 2011; the same magnitude is indicated by aircraft measurements above these regions upwind of the Baltimore/Washington airshed. With decreasing emissions of ozone precursors, the ground-level ozone in the Baltimore/Washington area shows a 0.6 ppbv yr−1 decrease in the past 15 yr. Since photochemical production of ozone is substantially influenced by ambient temperature, we introduce the climate penalty factor (CPF) into the trend analysis of long-term aircraft measurements. After compensating for inter-annual variations in temperature, historical aircraft measurements indicate that the daily net production of tropospheric ozone over the Baltimore/Washington area decreased from ∼20 ppbv day−1 in the late 1990s to ∼7 ppbv day−1 in the early 2010s during ozone season. A decrease in the long-term column ozone is observed as ∼0.2 DU yr−1 in the lowest 1500 m, corresponding to an improvement of ∼1.3 ppbv yr−1. Our aircraft measurements were conducted on days when severe ozone pollution was forecasted, and these results represent the decreasing trend in high ozone events over the past 15 yr. Back trajectory cluster analysis demonstrates that emissions of air pollutants from Ohio and Pennsylvania through Maryland influence the column abundances of downwind ozone in the lower atmosphere. The trends in air pollutants reveal the success of regulations implemented over the past decades and the importance of region-wide emission controls in the eastern United States.
Huang, M., K. W. Bowman, G. R. Carmichael, R. Bradley Pierce, H. M. Worden, M. Luo, O. R. Cooper, I. B. Pollack, T. B. Ryerson, and S. S. Brown (2013), Impact of Southern California anthropogenic emissions on ozone pollution in the mountain states: Model analysis and observational evidence from space, Journal of Geophysical Research: Atmospheres, 118(22), 12,784–12,803, doi:10.1002/2013JD020205.
The impact of Southern California (SoCal) anthropogenic emissions on ozone (O3) in the mountain states in May 2010 is studied using the Sulfur Transport and Deposition Model. We identified two to six major transport events from SoCal to different subregions in the mountain states, with transport times of 0–2 days indicated by trajectories, time-lag correlations, and forward/adjoint sensitivities. Based on forward sensitivity analysis, the contributions from SoCal anthropogenic emissions to the monthly mean daily maximum 8 h average (MDA8) surface O3 in the mountain states decrease with distance from SoCal, and they range from <1 ppbv (in Wyoming) to 15 ppbv (in western Arizona). These contributions show medium (>0.6) to strong (>0.8) positive correlations with the modeled total surface MDA8 O3. For the most strongly affected states of Arizona and New Mexico, these contributions have median values of 3, 2, 5, and 15 ppbv when the total surface MDA8 O3 exceeded thresholds of 60, 65, 70, and 75 ppbv, respectively. Surface MDA8 O3 values in SoCal show strong nonlinear responses to varied magnitudes of perturbation (e.g., ±50% and 100%) in SoCal anthropogenic emissions and weak nonlinear responses in the mountain states. Case studies show that different scales of transport (e.g., trans-Pacific, stratospheric intrusions, and interstate) can be dynamically and chemically coupled and simultaneously affect O3 in the mountain states when the meteorological conditions are favorable. During some of these strong transport periods, the contributions of SoCal anthropogenic emissions to hourly O3 in the mountain states can exceed 20 ppbv, close to the magnitude during a summer event reported by Langford et al. (2010). Satellite observations from the Tropospheric Emission Spectrometer and the Measurements of Pollution in the Troposphere multispectral retrievals qualitatively demonstrate large and interstate scales of transport, respectively. Suggestions are made for future satellite missions to measure O3 with improved spatial coverage, temporal frequency, and near-surface sensitivity to provide better observational constraints on interstate pollution transport studies.
Jiang, Z., D. B. A. Jones, H. M. Worden, M. N. Deeter, D. K. Henze, J. Worden, K. W. Bowman, C. a. M. Brenninkmeijer, and T. J. Schuck (2013), Impact of model errors in convective transport on CO source estimates inferred from MOPITT CO retrievals, Journal of Geophysical Research: Atmospheres, 118(4), 2073–2083, doi:10.1002/jgrd.50216.
Estimates of surface fluxes of carbon monoxide (CO) inferred from remote sensing observations or free tropospheric trace gas measurements using global chemical transport models can have significant uncertainties because of discrepancies in the vertical transport in the models, which make it challenging to unequivocally relate the observations back to the surface fluxes in the models. The new Measurement of Pollution in the Troposphere (MOPITT) version 5 retrievals provide greater sensitivity to lower tropospheric CO over land relative to the previous versions and are, therefore, useful for evaluating vertical transport in models. We have assimilated the new MOPITT CO retrievals, using the Goddard Earth Observing System (GEOS)-Chem model, to study the influence of vertical transport errors on inferred CO sources. We compared the source estimates obtained by assimilating the CO profiles, the column amounts, and the surface level retrievals for June–August 2006. The three different inversions produced large differences in the source estimates in regions of convection and strong CO emissions. The inversion using the CO profiles suggested an 85% increase in emissions in India/Southeast Asia, which exacerbated the model bias in the lower and middle troposphere, whereas using the surface level retrievals produced a 37% decrease in Indian/Southeast Asian emissions, which exacerbated the underestimate of CO in the upper troposphere. Globally, the inversion with the surface retrievals suggested a 22% reduction in emissions from the a priori estimate of 161 Tg CO/month (from combustion and the oxidation of biogenic volatile organic compounds), averaged in June–August 2006. The analysis results were validated with independent surface CO measurements from NOAA Global Monitoring Division (GMD) network and upper troposphere CO measurements from the Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrumented Container (CARIBIC). We found that the inversion with the surface retrievals agreed best with surface CO data but produced the largest discrepancy with the CARIBIC aircraft data in the upper troposphere, suggesting the influence of vertical transport errors in the model. Our results show that the comparison of the a posteriori CO distributions obtained from the inversions using the surface and profile retrievals provides a means of characterizing the potential impact of the vertical transport biases on the source estimates and the CO distribution.
Kumar, R., M. Naja, G. G. Pfister, M. C. Barth, and G. P. Brasseur (2013), Source attribution of carbon monoxide in India and surrounding regions during wintertime, Journal of Geophysical Research: Atmospheres, 118(4), 1981–1995, doi:10.1002/jgrd.50134.
This study presents a CO source contribution analysis for the atmosphere of South Asia during January–February 2008. The approach includes into the Weather Research and Forecasting Model with Chemistry 11 CO tracers, which track CO from different source types and regions. The comparison of model results with Measurement of Pollution in the Troposphere CO retrievals shows that the model reproduces the spatial, vertical, and temporal distributions of Measurement of Pollution in the Troposphere retrievals fairly well, but generally overestimates CO retrievals in the lower troposphere. CO mixing ratios averaged over the model domain at the surface, in the planetary boundary layer, and the free troposphere are estimated as 321 ± 291, 280 ± 208, and 125 ± 27 ppbv, respectively. Model results show that wintertime CO in the boundary layer and free troposphere over India is mostly due to anthropogenic emissions and to CO inflow. In the boundary layer, the contribution from anthropogenic sources dominates (40–90%), while in the free troposphere the main contribution is due to CO inflow from the lateral boundaries (50–90%). Over the Arabian Sea and the Bay of Bengal, 43–51% of surface CO mixing ratios come from the Indian subcontinent and 49–57% from regions outside of South Asia. The anthropogenic sources in the Indo-Gangetic Plain region are found to contribute, on average, 42% and 76% to anthropogenic surface CO over the Arabian Sea and the Bay of Bengal, respectively. The anthropogenic emissions from western and southern India contribute 49% to anthropogenic surface CO over the Arabian Sea. Anthropogenic emissions contribute only up to 40% over Burma where biomass burning plays a more important role. Regional transport contributes significantly to total anthropogenic CO over southern India (41%), Burma (49%), and even exceeds the contribution from local sources in western India (58%).
Naik, V., A. Voulgarakis, A. M. Fiore, L. W. Horowitz, J.-F. Lamarque, M. Lin, M. J. Prather, P. J. Young, D. Bergmann, P. J. Cameron-Smith, I. Cionni, W. J. Collins, S. B. Dalsøren, R. Doherty, V. Eyring, G. Faluvegi, G. A. Folberth, B. Josse, Y. H. Lee, I. A. MacKenzie, T. Nagashima, T. P. C. van Noije, D. A. Plummer, M. Righi, S. T. Rumbold, R. Skeie, D. T. Shindell, D. S. Stevenson, S. Strode, K. Sudo, S. Szopa, and G. Zeng (2013), Preindustrial to present-day changes in tropospheric hydroxyl radical and methane lifetime from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), Atmos. Chem. Phys., 13(10), 5277–5298, doi:10.5194/acp-13-5277-2013.
We have analysed time-slice simulations from 17 global models, participating in the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP), to explore changes in present-day (2000) hydroxyl radical (OH) concentration and methane (CH4) lifetime relative to preindustrial times (1850) and to 1980. A comparison of modeled and observation-derived methane and methyl chloroform lifetimes suggests that the present-day global multimodel mean OH concentration is overestimated by 5 to 10% but is within the range of uncertainties. The models consistently simulate higher OH concentrations in the Northern Hemisphere (NH) compared with the Southern Hemisphere (SH) for the present-day (2000; inter-hemispheric ratios of 1.13 to 1.42), in contrast to observation-based approaches which generally indicate higher OH in the SH although uncertainties are large. Evaluation of simulated carbon monoxide (CO) concentrations, the primary sink for OH, against ground-based and satellite observations suggests low biases in the NH that may contribute to the high north–south OH asymmetry in the models. The models vary widely in their regional distribution of present-day OH concentrations (up to 34 %). Despite large regional changes, the multi-model global mean (mass-weighted) OH concentration changes little over the past 150 yr, due to concurrent increases in factors that enhance OH (humidity, tropospheric ozone, nitrogen oxide (NOx) emissions, and UV radiation due to decreases in stratospheric ozone), compensated by increases in OH sinks (methane abundance, carbon monoxide and non-methane volatile organic carbon (NMVOC) emissions). The large inter-model diversity in the sign and magnitude of preindustrial to present-day OH changes (ranging from a decrease of 12.7% to an increase of 14.6 %) indicate that uncertainty remains in our understanding of the long-term trends in OH and methane lifetime. We show that this diversity is largely explained by the different ratio of the change in global mean tropospheric CO and NOx burdens (1CO/1NOx, approximately represents changes in OH sinks versus changes in OH sources) in the models, pointing to a need for better constraints on natural precursor emissions and on the chemical mechanisms in the current generation of chemistry-climate models. For the 1980 to 2000 period, we find that climate warming and a slight increase in mean OH (3.5±2.2 %) leads to a 4.3±1.9% decrease in the methane lifetime. Analysing sensitivity simulations performed by 10 models, we find that preindustrial to presentday climate change decreased the methane lifetime by about four months, representing a negative feedback on the climate system. Further, we analysed attribution experiments performed by a subset of models relative to 2000 conditions with only one precursor at a time set to 1860 levels. We find that global mean OH increased by 46.4±12.2% in response to preindustrial to present-day anthropogenic NOx emission increases, and decreased by 17.3±2.3 %, 7.6±1.5 %, and 3.1±3.0% due to methane burden, and anthropogenic CO, and NMVOC emissions increases, respectively.
Park, K., L. K. Emmons, Z. Wang, and J. E. Mak (2013), Large interannual variations in nonmethane volatile organic compound emissions based on measurements of carbon monoxide, Geophysical Research Letters, 40(1), 221–226, doi:10.1029/2012GL052303.
We present source estimates of atmospheric carbon monoxide from nonmethane volatile organic compound (NMVOC) oxidation during a period of 8 years (1997–2004) using a Bayesian inversion analysis. The optimized global NMVOC-derived CO source strength indicates a change of a factor of 2 between the 1997–1998 strong El Niño and subsequent La Niña conditions. For comparison, the average 8 year interannual variability (IAV) is 18%. The variation of NMVOC-derived CO is closely correlated with the Oceanic Niño Index (ONI) and surface temperature. A time-lagged correlation analysis between ONI and NMVOC-derived CO inventory indicated El Niño/Southern Oscillation leads the Northern Hemisphere (NH) NMVOC-derived CO production by about 3 months earlier than the Southern Hemisphere’s (SH). The SH NMVOC-derived CO was positively correlated with the lagged-ONI (r = 0.57), while the temperature change barely influenced SH NMVOC-derived CO (r = 0.01). In the NH, temperature was more robustly correlated with NMVOC-derived CO (r = 0.58) than the lagged-ONI (r = 0.35). In particular, the extra-tropical temperature showed a strong correlation (r = 0.90) with the NH NMVOC-derived CO and suggested its primary role in controlling the interannual variability of the NH NMVOC-derived CO.
Pommier, M., C. A. McLinden, and M. Deeter (2013), Relative changes in CO emissions over megacities based on observations from space, Geophysical Research Letters, 40(14), 3766–3771, doi:10.1002/grl.50704.
Urban areas are large sources of several air pollutants, with carbon monoxide (CO) among the largest. Yet measurement from space of their CO emissions remains elusive due to its long lifetime. Here we introduce a new method of estimating relative changes in CO emissions over megacities. A new multichannel Measurements of Pollution in the Troposphere (MOPITT) CO data product, offering improved sensitivity to the boundary layer, is used to estimate this relative change over eight megacities: Moscow, Paris, Mexico, Tehran, Baghdad, Los Angeles, Sao Paulo, and Delhi. By combining MOPITT observations with wind information from a meteorological reanalysis, changes in the CO upwind-downwind difference are used as a proxy for changes in emissions. Most locations show a clear reduction in CO emission between 2000–2003 and 2004–2008, reaching −43% over Tehran and −47% over Baghdad. There is a contrasted agreement between these results and the MACCity and Emission Database for Global Atmospheric Research v4.2 inventories.
Shindell, D. T., O. Pechony, A. Voulgarakis, G. Faluvegi, L. Nazarenko, J.-F. Lamarque, K. Bowman, G. Milly, B. Kovari, R. Ruedy, and G. A. Schmidt (2013), Interactive ozone and methane chemistry in GISS-E2 historical and future climate simulations, Atmos. Chem. Phys., 13(5), 2653–2689, doi:10.5194/acp-13-2653-2013.
Changes in climate and emissions will affect future air quality. In this work, simulations of regional air quality during current (2001–2005) and future (2026–2030) winter and summer are conducted with the newly released CMAQ version 5.0 to examine the impacts of simulated future climate and anthropogenic emission projections on air quality over the U.S. Current meteorological and chemical predictions are evaluated against observations to assess the model’s capability in reproducing the seasonal differences. WRF and CMAQ capture the overall observational spatial patterns and seasonal differences. Biases in model predictions are attributed to uncertainties in emissions, boundary conditions, and limitations in model physical and chemical treatments as well as the use of a coarse grid resolution. Increased temperatures (up to 3.18 °C) and decreased ventilation (up to 157 m in planetary boundary layer height) are found in both future winter and summer, with more prominent changes in winter. Increases in future temperatures result in increased isoprene and terpene emissions in winter and summer, driving the increase in maximum 8-h average O3 (up to 5.0 ppb) over the eastern U.S. in winter while decreases in NOx emissions drive the decrease in O3 over most of the U.S. in summer. Future PM2.5 concentrations in winter and summer and many of its components decrease due to decreases in primary anthropogenic emissions and the concentrations of secondary anthropogenic pollutants as well as increased precipitation in winter. Future winter and summer dry and wet deposition fluxes are spatially variable and increase with decreasing surface resistance and precipitation, respectively. They decrease with a decrease in ambient particulate concentrations. Anthropogenic emissions play a more important role in summer than in winter for future O3 and PM2.5 levels, with a dominance of the effects of significant emission reductions over those of climate change on future PM2.5 levels.
Silva, S. J., A. F. Arellano, and H. M. Worden (2013), Toward anthropogenic combustion emission constraints from space-based analysis of urban CO2/CO sensitivity, Geophysical Research Letters, 40(18), 4971–4976, doi:10.1002/grl.50954.
We explore the value of multispectral CO retrievals from NASA/Terra Measurement of Pollution In The Troposphere (MOPITT v5), along with Atmospheric CO2 Observations from Space (ACOSv2.9) CO2 retrievals from the Japan Aerospace Exploration Agency Greenhouse Gases Observing Satellite (GOSAT), for characterizing emissions from anthropogenic combustion. We use these satellite retrievals to analyze observed CO2/CO enhancement ratios (ΔCO2/ΔCO) over megacities. Since CO is coemitted with CO2 in anthropogenic combustion, the observed ΔCO2/ΔCO characterizes the general trend in combustion activity. Our analyses show patterns in ΔCO2/ΔCO that correspond well with the developed/developing status of megacities, and ΔCO2/ΔCO that agree well with available literature and emission inventories to approximately 20%. Comparisons with ΔCO2/ΔCO derived from Total Carbon Column Observing Network measurements show similar agreement, where some of the differences in observed ΔCO2/ΔCO are due to representativeness and limited GOSAT data. Our results imply potential constraints in anthropogenic combustion from GOSAT/MOPITT, particularly in augmenting our carbon monitoring systems.
Streets, D. G., T. Canty, G. R. Carmichael, B. de Foy, R. R. Dickerson, B. N. Duncan, D. P. Edwards, J. A. Haynes, D. K. Henze, M. R. Houyoux, D. J. Jacob, N. A. Krotkov, L. N. Lamsal, Y. Liu, Z. Lu, R. V. Martin, G. G. Pfister, R. W. Pinder, R. J. Salawitch, and K. J. Wecht (2013), Emissions estimation from satellite retrievals: A review of current capability, Atmospheric Environment, 77, 1011–1042, doi:10.1016/j.atmosenv.2013.05.051.
Abstract Since the mid-1990s a new generation of Earth-observing satellites has been able to detect tropospheric air pollution at increasingly high spatial and temporal resolution. Most primary emitted species can be measured by one or more of the instruments. This review article addresses the question of how well we can relate the satellite measurements to quantification of primary emissions and what advances are needed to improve the usability of the measurements by U.S. air quality managers. Built on a comprehensive literature review and comprising input by both satellite experts and emission inventory specialists, the review identifies several targets that seem promising: large point sources of NOx and SO2, species that are difficult to measure by other means (NH3 and CH4, for example), area sources that cannot easily be quantified by traditional bottom-up methods (such as unconventional oil and gas extraction, shipping, biomass burning, and biogenic sources), and the temporal variation of emissions (seasonal, diurnal, episodic). Techniques that enhance the usefulness of current retrievals (data assimilation, oversampling, multi-species retrievals, improved vertical profiles, etc.) are discussed. Finally, we point out the value of having new geostationary satellites like GEO-CAPE and TEMPO over North America that could provide measurements at high spatial (few km) and temporal (hourly) resolution.
Worden, H. M., D. P. Edwards, M. N. Deeter, D. Fu, S. S. Kulawik, J. R. Worden, and A. Arellano (2013a), Averaging kernel prediction from atmospheric and surface state parameters based on multiple regression for nadir-viewing satellite measurements of carbon monoxide and ozone, Atmos. Meas. Tech., 6(7), 1633–1646, doi:10.5194/amt-6-1633-2013.
A current obstacle to the observation system simulation experiments (OSSEs) used to quantify the potential performance of future atmospheric composition remote sensing systems is a computationally efficient method to define the scene-dependent vertical sensitivity of measurements as expressed by the retrieval averaging kernels (AKs). We present a method for the efficient prediction of AKs for multispectral retrievals of carbon monoxide (CO) and ozone (O-3) based on actual retrievals from MOPITT (Measurements Of Pollution In The Troposphere) on the Earth Observing System (EOS)-Terra satellite and TES (Tropospheric Emission Spectrometer) and OMI (Ozone Monitoring Instrument) on EOS-Aura, respectively. This employs a multiple regression approach for deriving scene-dependent AKs using predictors based on state parameters such as the thermal contrast between the surface and lower atmospheric layers, trace gas volume mixing ratios (VMRs), solar zenith angle, water vapor amount, etc. We first compute the singular value decomposition (SVD) for individual cloud-free AKs and retain the first three ranked singular vectors in order to fit the most significant orthogonal components of the AK in the subsequent multiple regression on a training set of retrieval cases. The resulting fit coefficients are applied to the predictors from a different test set of test retrievals cased to reconstruct predicted AKs, which can then be evaluated against the true retrieval AKs from the test set. By comparing the VMR profile adjustment resulting from the use of the predicted vs. true AKs, we quantify the CO and O-3 VMR profile errors associated with the use of the predicted AKs compared to the true AKs that might be obtained from a computationally expensive full retrieval calculation as part of an OSSE. Similarly, we estimate the errors in CO and O-3 VMRs from using a single regional average AK to represent all retrievals, which has been a common approximation in chemical OSSEs performed to date. For both CO and O-3 in the lower troposphere, we find a significant reduction in error when using the predicted AKs as compared to a single average AK. This study examined data from the continental United States (CONUS) for 2006, but the approach could be applied to other regions and times.
Worden, H. M., M. N. Deeter, C. Frankenberg, M. George, F. Nichitiu, J. Worden, I. Aben, K. W. Bowman, C. Clerbaux, P. F. Coheur, A. T. J. de Laat, R. Detweiler, J. R. Drummond, D. P. Edwards, J. C. Gille, D. Hurtmans, M. Luo, S. Martínez-Alonso, S. Massie, G. Pfister, and J. X. Warner (2013b), Decadal record of satellite carbon monoxide observations, Atmos. Chem. Phys., 13(2), 837–850, doi:10.5194/acp-13-837-2013.
Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend ~ −1 % yr−1 in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.
Worden, J., K. Wecht, C. Frankenberg, M. Alvarado, K. Bowman, E. Kort, S. Kulawik, M. Lee, V. Payne, and H. Worden (2013c), CH4 and CO distributions over tropical fires during October 2006 as observed by the Aura TES satellite instrument and modeled by GEOS-Chem, Atmos. Chem. Phys., 13(7), 3679–3692, doi:10.5194/acp-13-3679-2013.
Tropical fires represent a highly uncertain source of atmospheric methane (CH4) because of the variability of fire emissions and the dependency of the fire CH4 emission factors (g kg−1 dry matter burned) on fuel type and combustion phase. In this paper we use new observations of CH4 and CO in the free troposphere from the Aura Tropospheric Emission Sounder (TES) satellite instrument to place constraints on the role of tropical fire emissions versus microbial production (e.g. in wetlands and livestock) during the (October) 2006 El Niño, a time of significant fire emissions from Indonesia. We first compare the global CH4 distributions from TES using the GEOS-Chem model. We find a mean bias between the observations and model of 26.3 ppb CH4 that is independent of latitude between 50° S and 80° N, consistent with previous validation studies of TES CH4 retrievals using aircraft measurements. The slope of the distribution of CH4 versus CO as observed by TES and modeled by GEOS-Chem is consistent (within the TES observation error) for air parcels over the Indonesian peat fires, South America, and Africa. The CH4 and CO distributions are correlated between R = 0.42 and R = 0.46, with these correlations primarily limited by the TES random error. Over Indonesia, the observed slope of 0.13 (ppb ppb−1) ±0.01, as compared to a modeled slope of 0.153 (ppb ppb−1) ±0.005 and an emission ratio used within the GEOS-Chem model of approximately 0.11 (ppb ppb−1), indicates that most of the observed methane enhancement originated from the fire. Slopes of 0.47 (ppb ppb−1) ±0.04 and 0.44 (ppb ppb−1) ±0.03 over South America and Africa show that the methane in the observed air parcels primarily came from microbial-generated emissions. Sensitivity studies using GEOS-Chem show that part of the observed correlation for the Indonesian observations and most of the observed correlations over South America and Africa are a result of transport and mixing of the fire and nearby microbial-generated emissions into the observed air parcels. Differences between observed and modeled CH4 distributions over South America and southern Africa indicate that the magnitude of the methane emissions for this time period are inconsistent with observations even if the relative distribution of fire versus biotic emissions are consistent. This study shows the potential for estimation of CH4 emissions over tropical regions using joint satellite observations of CH4 and CO.
Worden, J., Z. Jiang, D. B. A. Jones, M. Alvarado, K. Bowman, C. Frankenberg, E. A. Kort, S. S. Kulawik, M. Lee, J. Liu, V. Payne, K. Wecht, and H. Worden (2013d), El Niño, the 2006 Indonesian peat fires, and the distribution of atmospheric methane, Geophysical Research Letters, 40(18), 4938–4943, doi:10.1002/grl.50937.
Dry conditions from a moderate El Niño during the fall of 2006 resulted in enhanced burning in Indonesia with fire emissions of CO approximately 4–6 times larger than the prior year. Here we use new tropospheric methane and CO data from the Aura Tropospheric Emission Spectrometer and new CO profile measurements from the Terra Measurements of Pollution in the Troposphere (MOPITT) satellite instruments with the Goddard Earth Observing System (GEOS)-Chem model to estimate methane emissions of 4.25 ± 0.75 Tg for October–November 2006 from these fires. Errors in convective parameterization in GEOS-Chem, evaluated by comparing MOPITT and GEOS-Chem CO profiles, are the primary uncertainty of the emissions estimate. The El Niño related Indonesian fires increased the tropical distribution of atmospheric methane relative to 2005, indicating that tropical biomass burning can compensate for expected decreases in tropical wetland methane emissions from reduced rainfall during El Niño as found in previous studies.
Yoon, J., A. Pozzer, P. Hoor, D. Y. Chang, S. Beirle, T. Wagner, S. Schloegl, J. Lelieveld, and H. M. Worden (2013), Technical Note: Temporal change in averaging kernels as a source of uncertainty in trend estimates of carbon monoxide retrieved from MOPITT, Atmos. Chem. Phys., 13(22), 11307–11316, doi:10.5194/acp-13-11307-2013.
It is now possible to monitor the global and long-term trends of trace gases that are important to atmospheric chemistry, climate, and air quality with satellite data records that span more than a decade. However, many of the remote sensing techniques used by satellite instruments produce measurements that have variable sensitivity to the vertical profiles of atmospheric gases. In the case of constrained retrievals like optimal estimation, this leads to a varying amount of a priori information in the retrieval and is represented by an averaging kernel. In this study, we investigate to what extent such trends can be biased by temporal changes of averaging kernels used in the retrieval algorithm. In particular, the surface carbon monoxide data retrieved from the Measurements Of Pollution In The Troposphere (MOPITT) instrument from 2001 to 2010 were analysed. As a practical example based on the MOPITT data, we show that if the true atmospheric mixing ratio is continuously 50% higher or lower than the a priori state, the temporal change of the averaging kernel at the surface level gives rise to an artificial trend in retrieved surface carbon monoxide, ranging from −10.71 to +13.21 ppbv yr−1 (−5.68 to +8.84% yr−1) depending on location. Therefore, in the case of surface (or near-surface level) CO derived from MOPITT, the AKs trends multiplied by the difference between true and a priori states must be quantified in order to estimate trend biases.


Boynard, A., G. G. Pfister, and D. P. Edwards (2012), Boundary layer versus free tropospheric CO budget and variability over the United States during summertime, Journal of Geophysical Research: Atmospheres, 117(D4), n/a–n/a, doi:10.1029/2011JD016416.
The regional Weather Research and Forecasting Model with Chemistry (WRF-Chem) version 3.2 is used to analyze the carbon monoxide (CO) budget and spatiotemporal variability over the United States in summer 2008. CO tracers for different emission sources are used to separate the modeled CO fields into the contributions from individual sources (pollution inflow to the model domain, chemical production within the model domain, and local emissions by type). The implementation of tagged CO tracers into WRF-Chem constitutes an innovative aspect of this work. We evaluate WRF-Chem CO concentrations using aircraft, satellite, and surface observations. The model reproduces fairly well the observed CO concentrations for the entire altitude range but tends to underestimate fire emissions and overestimate anthropogenic sources and CO from pollution inflow. Evaluation results also show that the model gives a good representation of background CO mixing ratios with mean biases better than ∼15 ppbv in the free troposphere (FT) and less than 20 ppbv toward the surface. The analysis of the CO budget over the contiguous United States shows that at the surface, CO from inflow is the dominant source, with a mean relative contribution of 63 ± 19%. Anthropogenic and photochemically produced CO contribute to surface CO to a lesser extent (18 ± 14% and 14 ± 8%, respectively). The average contribution from fire emissions to surface CO during the period examined is small (2 ± 5%) but can have a large impact in certain regions and times. Similar trends are found in the planetary boundary layer (PBL). In the FT, the average CO relative contributions are estimated as 84 ± 12% for CO from inflow, 5 ± 4% for anthropogenic CO, 9 ± 7% for photochemically produced CO, and 1 ± 5% for CO from fires. Using WRF-Chem simulations, we also examine the representation of surface and PBL CO concentration variability that would be captured by current near infrared (NIR) and thermal infrared (TIR) satellite observations. We find that CO total columns are impacted by variability in the lowermost troposphere (LMT) at the ∼10% level, indicating limited sensitivity for air quality applications. The same is generally true for the FT CO column obtained from TIR measurements, although this does provide a good measure for capturing the pollution inflow variability and is therefore valuable in providing initial and boundary conditions to constrain regional models. We further analyze the situations under which the LMT concentrations obtained from recently demonstrated multispectral (NIR + TIR) observations capture the surface CO variability.
Deeter, M. N., H. M. Worden, D. P. Edwards, J. C. Gille, and A. E. Andrews (2012), Evaluation of MOPITT retrievals of lower-tropospheric carbon monoxide over the United States, Journal of Geophysical Research: Atmospheres, 117(D13), n/a–n/a, doi:10.1029/2012JD017553.
The new Version 5 MOPITT (Measurements of Pollution in the Troposphere) product for carbon monoxide (CO) is the first satellite product to exploit simultaneous near-infrared and thermal-infrared observations to enhance retrieval sensitivity in the lower troposphere. This feature is important to air quality analyses and studies of CO sources. However, because of the influence of both thermal contrast and geophysical noise, the retrieval characteristics for this new multispectral product are highly variable. New V5 products for surface-level CO concentrations have been evaluated over the contiguous United States using both in situ vertical profiles and NOAA ground-based “Tall Tower” measurements. Validation results based on the in situ profiles indicate that retrieval biases are on the order of a few percent. However, direct comparisons with the Tall Tower measurements demonstrate that smoothing error, which depends on both the retrieval averaging kernels and CO variability in the lower troposphere, exhibits significant geographical and seasonal variability.
Drori, R., U. Dayan, D. P. Edwards, L. K. Emmons, and C. Erlick (2012), Attributing and quantifying carbon monoxide sources affecting the Eastern Mediterranean: a combined satellite, modelling, and synoptic analysis study, Atmos. Chem. Phys., 12(2), 1067–1082, doi:10.5194/acp-12-1067-2012.
Pollutants from global sources are known to affect the Eastern Mediterranean Shore (EMS). However, there has been no previous study explicitly locating the European sources, characterizing their transport pathways, and quantifying their contribution to local concentrations in the EMS. In the current study, spatially tagged carbon monoxide was used as a tracer for pollutant transport from Europe to the EMS over five consecutive years (2003-2007) using the global chemical transport model MOZART-4. The model results were compared against NOAA/GMD ground station data and remotely sensed data from the Terra/MOPITT satellite and found to agree well on monthly basis but do not agree on daily basis. On synoptic scale, there is agreement between MOZART and GMD during July to August. A budget analysis reveals the role of CO from hydrocarbon oxidation on CO concentration during summer. European anthropogenic emissions were found to significantly influence EM surface concentrations, while European biomass burning (BB) emissions were found to have only a small impact on EM surface concentrations. Over the five simulated years, only two European biomass burning episodes contributed more than 10 ppb to surface CO concentrations in the EM. CO enhancement in the EM during the summer was attributed to synoptic conditions prone to favorable transport from Turkey and Eastern Europe towards the EM rather than increased emissions. We attribute the apparently misleading association between CO emitted from European BB and CO enhancements over the EM to typical summer synoptic conditions caused by the lingering of an anticyclone positioned over the Western and Central Mediterranean Basin that lead to forest fires in the area. Combined with a barometric trough over the eastern part of the Mediterranean Basin, this generates a prevailing transport of air masses from Eastern Europe to the EMS. Synoptic scale variations are shown to change the transport pathways from Europe towards the EMS having an overall small affect. CO concentration over the EMS can be describe as having 3 components: the seasonal cycle, the cycle of CO produced from hydrocarbon oxidation and a synoptic variation.
Fortems-Cheiney, A., F. Chevallier, I. Pison, P. Bousquet, M. Saunois, S. Szopa, C. Cressot, T. P. Kurosu, K. Chance, and A. Fried (2012), The formaldehyde budget as seen by a global-scale multi-constraint and multi-species inversion system, Atmos. Chem. Phys., 12(15), 6699–6721, doi:10.5194/acp-12-6699-2012.
For the first time, carbon monoxide (CO) and formaldehyde (HCHO) satellite retrievals are used together with methane (CH4) and methyl choloroform (CH3CCl3 or MCF) surface measurements in an advanced inversion system. The CO and HCHO are respectively from the MOPITT and OMI instruments. The multi-species and multi-satellite dataset inversion is done for the 2005-2010 period. The robustness of our results is evaluated by comparing our posterior-modeled concentrations with several sets of independent measurements of atmospheric mixing ratios. The inversion leads to significant changes from the prior to the posterior, in terms of magnitude and seasonality of the CO and CH4 surface fluxes and of the HCHO production by non-methane volatile organic compounds (NMVOC). The latter is significantly decreased, indicating an overestimation of the biogenic NMVOC emissions, such as isoprene, in the GEIA inventory. CO and CH4 surface emissions are increased by the inversion, from 1037 to 1394 TgCO and from 489 to 529 TgCH(4) on average for the 2005-2010 period. CH4 emissions present significant interannual variability and a joint CO-CH4 fluxes analysis reveals that tropical biomass burning probably played a role in the recent increase of atmospheric methane.
Herron-Thorpe, F. L., G. H. Mount, L. K. Emmons, B. K. Lamb, S. H. Chung, and J. K. Vaughan (2012), Regional air-quality forecasting for the Pacific Northwest using MOPITT/TERRA assimilated carbon monoxide MOZART-4 forecasts as a near real-time boundary condition, Atmos. Chem. Phys., 12(12), 5603–5615, doi:10.5194/acp-12-5603-2012.
Results from a regional air quality forecast model, AIRPACT-3, were compared to AIRS carbon monoxide column densities for the spring of 2010 over the Pacific Northwest. AIRPACT-3 column densities showed high correlation (R > 0.9) but were significantly biased (similar to 25%) with consistent under-predictions for spring months when there is significant transport from Asia. The AIRPACT-3 CO bias relative to AIRS was eliminated by incorporating dynamic boundary conditions derived from NCAR’s MOZART forecasts with assimilated MOPITT carbon monoxide. Changes in ozone-related boundary conditions derived from MOZART forecasts are also discussed and found to affect background levels by +/- 10 ppb but not found to significantly affect peak ozone surface concentrations.
Hooghiemstra, P. B., M. C. Krol, P. Bergamaschi, A. T. J. de Laat, G. R. van der Werf, P. C. Novelli, M. N. Deeter, I. Aben, and T. Röckmann (2012a), Comparing optimized CO emission estimates using MOPITT or NOAA surface network observations, Journal of Geophysical Research: Atmospheres, 117(D6), n/a–n/a, doi:10.1029/2011JD017043.
This paper compares two global inversions to estimate carbon monoxide (CO) emissions for 2004. Either surface flask observations from the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) or CO total columns from the Measurement of Pollution in the Troposphere (MOPITT) instrument are assimilated in a 4D-Var framework. Inferred emission estimates from the two inversions are consistent over the Northern Hemisphere (NH). For example, both inversions increase anthropogenic CO emissions over Europe (from 46 to 94 Tg CO/yr) and Asia (from 222 to 420 Tg CO/yr). In the Southern Hemisphere (SH), three important findings are reported. First, due to their different vertical sensitivity, the stations-only inversion increases SH biomass burning emissions by 108 Tg CO/yr more than the MOPITT-only inversion. Conversely, the MOPITT-only inversion results in SH natural emissions (mainly CO from oxidation of NMVOCs) that are 185 Tg CO/yr higher compared to the stations-only inversion. Second, MOPITT-only derived biomass burning emissions are reduced with respect to the prior which is in contrast to previous (inverse) modeling studies. Finally, MOPITT derived total emissions are significantly higher for South America and Africa compared to the stations-only inversion. This is likely due to a positive bias in the MOPITT V4 product. This bias is also apparent from validation with surface stations and ground-truth FTIR columns. Our results show that a combined inversion is promising in the NH. However, implementation of a satellite bias correction scheme is essential to combine both observational data sets in the SH.
Hooghiemstra, P. B., M. C. Krol, T. T. van Leeuwen, G. R. van der Werf, P. C. Novelli, M. N. Deeter, I. Aben, and T. Röckmann (2012b), Interannual variability of carbon monoxide emission estimates over South America from 2006 to 2010, Journal of Geophysical Research: Atmospheres, 117(D15), n/a–n/a, doi:10.1029/2012JD017758.
We present the first inverse modeling study to estimate CO emissions constrained by both surface and satellite observations. Our 4D-Var system assimilates National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA/ESRL) Global Monitoring Division (GMD) surface and Measurements Of Pollution In The Troposphere (MOPITT) satellite observations jointly by fitting a bias correction scheme. This approach leads to the identification of a positive bias of maximum 5 ppb in MOPITT column-averaged CO mixing ratios in the remote Southern Hemisphere (SH). The 4D-Var system is used to estimate CO emissions over South America in the period 2006–2010 and to analyze the interannual variability (IAV) of these emissions. We infer robust, high spatial resolution CO emission estimates that show slightly smaller IAV due to fires compared to the Global Fire Emissions Database (GFED3) prior emissions. South American dry season (August and September) biomass burning emission estimates amount to 60, 92, 42, 16 and 93 Tg CO/yr for 2006 to 2010, respectively. Moreover, CO emissions probably associated with pre-harvest burning of sugar cane plantations in São Paulo state are underestimated in current inventories by 50–100%. We conclude that climatic conditions (such as the widespread drought in 2010) seem the most likely cause for the IAV in biomass burning CO emissions. However, socio-economic factors (such as the growing global demand for soy, beef and sugar cane ethanol) and associated deforestation fires, are also likely as drivers for the IAV of CO emissions, but are difficult to link directly to CO emissions.
Kumar, R., M. Naja, G. G. Pfister, M. C. Barth, C. Wiedinmyer, and G. P. Brasseur (2012), Simulations over South Asia using the Weather Research and Forecasting  model with Chemistry (WRF-Chem): chemistry evaluation and initial  results, Geosci. Model Dev., 5(3), 619–648, doi:10.5194/gmd-5-619-2012.
This study presents annual simulations of tropospheric ozone and related species made for the first time using the WRF-Chem model over South Asia for the year 2008. The model-simulated ozone, CO, and NOx are evaluated against ground-based, balloon-borne and satellite-borne (TES, OMI and MOPITT) observations. The comparison of model results with surface ozone observations from seven sites and CO and NOx observations from three sites indicate the model’s ability in reproducing seasonal variations of ozone and CO, but show some differences in NOx. The modeled vertical ozone distribution agrees well with the ozone soundings data from two Indian sites. The vertical distributions of TES ozone and MOPITT CO are generally well reproduced, but the model underestimates TES ozone, OMI tropospheric column NO2 and MOPITT total column CO retrievals during all the months, except MOPITT retrievals during August-January and OMI retrievals during winter. Largest differences between modeled and satellite-retrieved quantities are found during spring when intense biomass burning activity occurs in this region. The evaluation results indicate large uncertainties in anthropogenic and biomass burning emission estimates, especially for NOx. The model results indicate clear regional differences in the seasonality of surface ozone over South Asia, with estimated net ozone production during daytime (1130-1530 h) over inland regions of 0-5 ppbv h(-1) during all seasons and of 0-2 ppbv h(-1) over marine regions during outflow periods. The model results indicate that ozone production in this region is mostly NOx-limited. This study shows that WRF-Chem model captures many important features of the observations and gives confidence to using the model for understanding the spatio-temporal variability of ozone over South Asia. However, improvements of South Asian emission inventories and simulations at finer model resolution, especially over the complex Himalayan terrain in northern India, are also essential for accurately simulating ozone in this region.
Martinez-Alonso, S., M. N. Deeter, H. M. Worden, C. Clerbaux, D. Mao, and J. C. Gille (2012), First satellite identification of volcanic carbon monoxide, Geophys. Res. Lett., 39, doi:10.1029/2012GL053275.
Volcanic degassing produces abundant H2O and CO2, as well as SO2, HCl, H2S, S-2, H-2, HF, CO, and SiF4. Volcanic SO2, HCl, and H2S have been detected from satellites in the past; the remaining species are analyzed in situ or using airborne instruments, with all the consequent limitations in safety and sampling, and at elevated costs. We report identification of high CO concentrations consistent with a volcanic origin (the 2010 Eyjafjallajokull and 2011 Grimsvotn eruptions in Iceland) in data from the Measurements of Pollution in the Troposphere instrument (MOPITT) onboard EOS/Terra. The high CO values coincide spatially and temporally with ash plumes emanating from the eruptive centers, with elevated SO2 and aerosol optical thickness, as well as with high CO values in data from the Infrared Atmospheric Sounding Interferometer (IASI), onboard MetOp-A. CO has a positive indirect radiative forcing; climate models currently do not account for volcanic CO emissions. Given global volcanic CO2 emissions between 130 and 440 Tg/year and volcanic CO: CO2 ratios from the literature, we estimate that average global volcanic CO emissions may be on the order of similar to 5.5 Tg/year, equivalent to the CO emissions caused by combined fossil fuel and biofuel combustion in Australia. Citation: Martinez-Alonso, S., M. N. Deeter, H. M. Worden, C. Clerbaux, D. Mao, and J. C. Gille (2012), First satellite identification of volcanic carbon monoxide, Geophys. Res. Lett., 39, L21809, doi:10.1029/2012GL053275.
Parrington, M., P. I. Palmer, D. K. Henze, D. W. Tarasick, E. J. Hyer, R. C. Owen, D. Helmig, C. Clerbaux, K. W. Bowman, M. N. Deeter, E. M. Barratt, P.-F. Coheur, D. Hurtmans, Z. Jiang, M. George, and J. R. Worden (2012), The influence of boreal biomass burning emissions on the distribution of tropospheric ozone over North America and the North Atlantic during 2010, Atmos. Chem. Phys., 12(4), 2077–2098, doi:10.5194/acp-12-2077-2012.
We have analysed the sensitivity of the tropospheric ozone distribution over North America and the North Atlantic to boreal biomass burning emissions during the summer of 2010 using the GEOS-Chem 3-D global tropospheric chemical transport model and observations from in situ and satellite instruments. We show that the model ozone distribution is consistent with observations from the Pico Mountain Observatory in the Azores, ozonesondes across Canada, and the Tropospheric Emission Spectrometer (TES) and Infrared Atmospheric Sounding Instrument (IASI) satellite instruments. Mean biases between the model and observed ozone mixing ratio in the free troposphere were less than 10 ppbv. We used the adjoint of GEOS-Chemto show the model ozone distribution in the free troposphere over Maritime Canada is largely sensitive to NOx emissions from biomass burning sources in Central Canada, lightning sources in the central US, and anthropogenic sources in the eastern US and southeastern Canada. We also used the adjoint of GEOS-Chem to evaluate the Fire Locating And Monitoring of Burning Emissions (FLAMBE) inventory through assimilation of CO observations from the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument. The CO inversion showed that, on average, the FLAMBE emissions needed to be reduced to 89% of their original values, with scaling factors ranging from 12% to 102 %, to fit the MOPITT observations in the boreal regions. Applying the CO scaling factors to all species emitted from boreal biomass burning sources led to a decrease of the model tropospheric distributions of CO, PAN, and NOx by as much as -20 ppbv, -50 pptv, and -20 pptv respectively. The modification of the biomass burning emission estimates reduced the model ozone distribution by approximately -3 ppbv (-8%) and on average improved the agreement of the model ozone distribution compared to the observations throughout the free troposphere, reducing the mean model bias from 5.5 to 4.0 ppbv for the Pico Mountain Observatory, 3.0 to 0.9 ppbv for ozonesondes, 2.0 to 0.9 ppbv for TES, and 2.8 to 1.4 ppbv for IASI.
Worden, H. M., Y. Cheng, G. Pfister, G. R. Carmichael, Q. Zhang, D. G. Streets, M. Deeter, D. P. Edwards, J. C. Gille, and J. R. Worden (2012), Satellite-based estimates of reduced CO and CO2 emissions due to traffic  restrictions during the 2008 Beijing Olympics, Geophys. Res. Lett., 39, L14802, doi:10.1029/2012GL052395.
During the 2008 Olympics, the Chinese government made a significant effort to improve air quality in Beijing, including restrictions on traffic. Here we estimate the reductions in carbon monoxide (CO) and carbon dioxide (CO2) emissions resulting from the control measures on Beijing transportation. Using MOPITT (Measurements Of Pollution In The Troposphere) multispectral satellite observations of near-surface CO along with WRF-Chem (Weather Research and Forecasting model with Chemistry) simulations for Beijing during August, 2007 and 2008, we estimate changes in CO due to meteorology and transportation sector emissions. Applying a reported CO/CO2 emission ratio for fossil fuels, we find the corresponding reduction in CO2, 60 +/- 36 Gg[CO2]/day. As compared to emission scenarios being considered for the IPCC AR5 (Intergovernmental Panel on Climate Change, 5th Assessment Report), this result suggests that urban traffic controls on the Beijing Olympics scale could play a significant role in meeting target reductions for global CO2 emissions. Citation: Worden, H.M., Y. Cheng, G. Pfister, G.R. Carmichael, Q. Zhang, D.G. Streets, M. Deeter, D.P. Edwards, J.C. Gille, and J.R. Worden (2012), Satellite-based estimates of reduced CO and CO2 emissions due to traffic restrictions during the 2008 Beijing Olympics, Geophys. Res. Lett., 39, L14802, doi:10.1029/2012GL052395.


Deeter, M. N., H. M. Worden, J. C. Gille, D. P. Edwards, D. Mao, and J. R. Drummond (2011), MOPITT multispectral CO retrievals: Origins and effects of geophysical radiance errors, Journal of Geophysical Research: Atmospheres, 116(D15), n/a–n/a, doi:10.1029/2011JD015703.
An obstacle to the simultaneous use of near-infrared (NIR) and thermal infrared (TIR) observations from the Measurements of Pollution in the Troposphere (MOPITT) instrument has been a lack of understanding of NIR radiance errors. Retrieval uncertainties produced by optimal estimation-based retrieval algorithms used for satellite instruments like MOPITT are only meaningful if radiance error statistics are accurately quantified in the measurement error covariance matrix. MOPITT’s gas correlation radiometers are subject to a unique form of “geophysical noise” due to the combined effects of (1) translational motion of the instrumental field of view during a single observation and (2) fine-scale spatial variability of surface radiative properties. We describe and demonstrate a new method for quantifying this source of error for each observation. Both TIR and NIR radiance errors due to this effect are highly variable, especially over land, but are qualitatively consistent with the variability of Moderate Resolution Imaging Spectroradiometer radiances in similar spectral bands. In addition, retrieval algorithm modifications are described which adjust the trade-off between smoothing error and retrieval noise within the optimal estimation framework. These modifications are necessary to fully exploit the information in MOPITT’s NIR channels. A case study based on MOPITT observations over Minnesota demonstrates significant improvement in retrieval performance as the result of the retrieval algorithm modifications.
Fortems-Cheiney, A., F. Chevallier, I. Pison, P. Bousquet, S. Szopa, M. N. Deeter, and C. Clerbaux (2011), Ten years of CO emissions as seen from Measurements of Pollution in the Troposphere (MOPITT), Journal of Geophysical Research (Atmospheres), 116(d15), 5304, doi:10.1029/2010JD014416.
The Measurements of Pollution in the Troposphere (MOPITT) retrievals are used as top-down constraints in an inversion for global CO emissions, for the past 10 years (from March 2000 to December 2009), at 8 day and 3.75° × 2.75° (longitude, latitude) resolution. The method updates a standard prior inventory and yields large increments in terms of annual regional budgets and seasonality. Our validation strategy consists in comparing our posterior-modeled concentrations with several sets of independent measurements: surface measurements, aircraft, and satellite. The posterior emissions, with a global 10 year average of 1430 TgCO/yr, are 37% higher than the prior ones, built from the EDGAR 3.2 and the GFEDv2 inventories (1038 TgCO/yr on average). In addition, they present some significant seasonal variations in the Northern Hemisphere that are not present in our prior nor in others’ major inventories. Our results also exhibit some large interannual variability due to biomass burning emissions, climate, and socioeconomic factors; CO emissions range from 1504 TgCO (in 2007) to 1318 TgCO (in 2009).
Illingworth, S. M., J. J. Remedios, H. Boesch, S.-P. Ho, D. P. Edwards, P. I. Palmer, and S. Gonzi (2011), A comparison of OEM CO retrievals from the IASI and MOPITT instruments, Atmospheric Measurement Techniques, 4, 775–793, doi:10.5194/amt-4-775-2011.
Observations of atmospheric carbon monoxide (CO) can only be made on continental and global scales by remote sensing instruments situated in space. One such instrument is the Infrared Atmospheric Sounding Interferometer (IASI), producing spectrally resolved, top-of-atmosphere radiance measurements from which CO vertical layers and total columns can be retrieved. This paper presents a technique for intercomparisons of satellite data with low vertical resolution. The example in the paper also generates the first intercomparison between an IASI CO data set, in this case that produced by the University of Leicester IASI Retrieval Scheme (ULIRS), and the V3 and V4 operationally retrieved CO products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument. The comparison is performed for a localised region of Africa, primarily for an ocean day-time configuration, in order to develop the technique for instrument intercomparison in a region with well defined a priori. By comparing both the standard data and a special version of MOPITT data retrieved using the ULIRS a priori for CO, it is shown that standard intercomparisons of CO are strongly affected by the differing a priori data of the retrievals, and by the differing sensitivities of the two instruments. In particular, the differing a priori profiles for MOPITT V3 and V4 data result in systematic retrieved profile changes as expected. An application of averaging kernels is used to derive a difference quantity which is much less affected by smoothing error, and hence more sensitive to systematic error. These conclusions are confirmed by simulations with model profiles for the same region. This technique is used to show that for the data that has been processed the systematic bias between MOPITT V4 and ULIRS IASI data, at MOPITT vertical resolution, is less than 7 % for the comparison data set, and on average appears to be less than 4 %. The results of this study indicate that intercomparisons of satellite data sets with low vertical resolution should ideally be performed with: retrievals using a common a priori appropriate to the geographic region studied; the application of averaging kernels to compute difference quantities with reduced a priori influence; and a comparison with simulated differences using model profiles for the target gas in the region.
Ott, L., S. Pawson, and J. Bacmeister (2011), An analysis of the impact of convective parameter sensitivity on simulated global atmospheric CO distributions, Journal of Geophysical Research: Atmospheres, 116(D21), n/a–n/a, doi:10.1029/2011JD016077.
In an effort to better understand how uncertainty in simulated convection propagates into simulations of global trace gas distributions, we have constructed an eight-member ensemble of simulations using NASA’s Goddard Earth Observing System Version 5 (GEOS-5) general circulation model (GCM). The ensemble was created by perturbing parameters in the model’s moist physics schemes found to strongly influence the magnitude of convective mass flux. Globally, ensemble spreads in column CO are typically small (less than 4% of the mean column value) and, in many areas, are not significantly different from internal model variability. The largest ensemble spreads are found near source regions and outflow pathways. At the majority of remote surface monitoring sites, the annual mean ensemble spread is less than 5%, indicating that these locations, which are often the basis of inversion studies, are relatively insensitive to uncertainty in the representation of convection. We also examine in greater detail two simulations in which the magnitude of convective mass flux is significantly altered. Changes to convective parameters strongly influence grid-scale vertical and turbulent transport processes in addition to convective mass flux. Despite large differences in the magnitude of convective mass fluxes, this compensating behavior by other model processes results in comparable atmospheric residence times in the two simulations and largely similar global CO distributions. The results indicate that convective mass flux is strongly related to other vertical transport processes in a GCM and cannot be viewed as entirely separate. Future studies of the role of convective transport need to consider the relationship between convective and total mass flux.
Pfister, G. G., J. Avise, C. Wiedinmyer, D. P. Edwards, L. K. Emmons, G. D. Diskin, J. Podolske, and A. Wisthaler (2011), CO source contribution analysis for California during ARCTAS-CARB, Atmos. Chem. Phys., 11(15), 7515–7532, doi:10.5194/acp-11-7515-2011.
Air pollution is of concern in many parts of California and is impacted by both local emissions and also by pollution inflow from the North Pacific Ocean. In this study, we use the regional chemical transport model WRF-Chem V3.2 together with the global Model for OZone and Related Chemical Tracers to examine the CO budget over California. We include model CO tracers for different emission sources in the models, which allow estimation of the relative importance of local sources versus pollution inflow on the distribution of CO at the surface and in the free troposphere. The focus of our study is on the 15 June-15 July 2008 time period, which coincides with the aircraft deployment of the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission over California. Model simulations are evaluated using these aircraft observations as well as satellite retrievals and surface observations of CO. Evaluation results show that the model overall predicts the observed CO fields well, but points towards an underestimate of CO from the fires in Northern California, which had a strong influence during the study period, and towards a slight overestimate of CO from pollution inflow and local anthropogenic sources. The analysis of the CO budget over California reveals that inflow of CO explains on average 99 +/- 11 ppbV of surface CO during the study period, compared to 61 +/- 95 ppbV for local anthropogenic direct emissions of CO and 84 +/- 194 ppbV for fires. In the free troposphere, the average CO contributions are estimated as 96 +/- 7 ppbV for CO inflow, 8 +/- 9 ppbV for CO from local anthropogenic sources and 18 +/- 13 ppbV for CO from fires. Accounting for the low bias in the CO fire emission inventory, the fire impact during the study period might have been up to a factor 4 higher than the given estimates.
Tilmes, S., L. K. Emmons, K. S. Law, G. Ancellet, H. Schlager, J.-D. Paris, H. E. Fuelberg, D. G. Streets, C. Wiedinmyer, G. S. Diskin, Y. Kondo, J. Holloway, J. P. Schwarz, J. R. Spackman, T. Campos, P. Nédélec, and M. V. Panchenko (2011), Source contributions to Northern Hemisphere CO and black carbon during spring and summer 2008 from POLARCAT and START08/preHIPPO observations and MOZART-4, Atmospheric Chemistry and Physics Discussions, 11(2), 5935–5983, doi:10.5194/acpd-11-5935-2011.
Anthropogenic pollution and wildfires are main producers of carbon monoxide (CO) and black carbon (BC) in the Northern Hemisphere. High concentrations of these compounds are transported into the Arctic troposphere, influencing the ecosystem in high northern latitudes and the global climate. The global chemical transport model MOZART-4 is used to quantify the seasonal evolution of the contribution of CO and BC from different source regions in spring and summer 2008 by tagging their emissions. Aircraft observations from the POLARCAT experiments, in particular NASA ARCTAS, NOAA ARCPAC, POLARCAT-France, DLR GRACE and YAK-AEROSIB, as well as the NSF START08/preHIPPO experiments during Spring-Summer 2008 are combined to quantify the representation of simulated tracer characteristics in anthropogenic and fire plumes. In general, the model reproduces CO and BC well. Based on aircraft measurements and FLEXPART back-trajectories, the altitude contribution of emissions coming from different source regions is well captured in the model. Uncertainties of the MOZART-4 model are identified by comparing the data with model results on the flight tracks and using MOPITT satellite observations. Anthropogenic emissions are underestimated by about 10% in high northern latitudes in spring, and shortcomings exist in simulating fire plumes. The remote impact of East-Siberian fire emissions is underestimated for spring, whereas the impact of Southeast Asian fire emissions to mid-latitude CO values is overestimated by the model. In summer, mid-latitude CO values agree well between model and observations, whereas summer high latitude East-Siberian fire emissions in the model are overestimated by 20% in comparison to observations in the region. On the other hand, CO concentrations are underestimated by about 30% over Alaska and Canada at altitudes above 4 km. BC values are overestimated by the model at altitudes above 4 km in summer. Based on MOZART-4, with tagged CO and BC tracers, anthropogenic emissions of Asia, Europe and the US have the largest contribution to the CO and BC in mid- and high latitudes in spring and summer. Southeast Asian, Chinese and Indian fires have a large impact on CO pollution in spring in low latitudes with a maximum between 20° and 30°, whereas Siberian fires contribute largely to the pollution in high latitudes, up to 10% in spring and up to 30% in summer. The largest contributions to BC values in high latitudes are from anthropogenic emissions (about 70%). CO and BC have larger mass loadings in April than in July, as a result of photochemistry and dynamics.
Zhang, Y. (2011), Mean global and regional distributions of MOPITT carbon monoxide during 2000–2009 and during ENSO, Atmospheric Environment, 45(6), 1347–1358, doi:10.1016/j.atmosenv.2010.11.044.
The MOPITT (Measurements Of Pollution In The Troposphere) CO measurements over a 10-year period (2000–2009) reveal consistently positive trends on the order of 0.13–0.19 × 1016 mol cm−2 per month in CO total column concentrations over the entire globe and the hemispheres. Two maxima in globally averaged CO concentrations are identified: one in April and one in October, with two minima in July and December. These maxima and minima are attributable to the respective maxima and minima in CO concentrations over the Northern and Southern Hemispheres. Over the Tropics, maximum and minimum CO concentrations are noted in October and June, respectively, due primarily to biomass burning.  During El Niño DJF (December–January–February) and JJA (June–July–August), predominantly positive anomalies in CO total column are noted over the entire globe except for the high latitudes of both hemispheres and the central part of the South America where negative anomalies are identified. La Niña DJF and JJA are largely opposite to El Niño DJF and JJA in CO total column anomalies. Negative (positive) anomalies in CO total column tend to be associated with wet (dry) anomalies in precipitation over the major polluted areas during ENSO. It is suggested that changes in the atmospheric circulations during ENSO either enhance or weaken precipitation systems with the associated precipitation modulating CO total column. The correspondence between anomalies in CO total column and anomalies in Terra MODIS fire pixels during ENSO is rather poor over many parts of the world.


Arellano, A. F., P. G. Hess, D. P. Edwards, and D. Baumgardner (2010), Constraints on black carbon aerosol distribution from Measurement of Pollution in the Troposphere (MOPITT) CO, Geophysical Research Letters, 37(17), 17801, doi:10.1029/2010GL044416.
We present an approach to constrain simulated atmospheric black carbon (BC) using carbon monoxide (CO) observations. The approach uses: (1) the Community Atmosphere Model with Chemistry to simulate the evolution of BC and CO within an ensemble of model simulations; (2) satellite CO retrievals from the MOPITT/Terra instrument to assimilate observed CO into these simulations; (3) the derived sensitivity of BC to CO within these simulations to correct the simulated BC distributions. We demonstrate the performance of this approach through model experiments with and without the BC corrections during the period coinciding with the Intercontinental Chemical Transport Experiment (INTEX-B). Our results show significant improvements (∼50%) in median BC profiles using constraints from MOPITT, based on comparisons with INTEX-B measurements. We find that assimilating MOPITT CO provides considerable impact on simulated BC concentrations, especially over source regions. This approach offers an opportunity to augment our current ability to predict BC distributions.
Claeyman, M., J.-L. Attié, L. El Amraoui, D. Cariolle, V.-H. Peuch, H. Teyssèdre, B. Josse, P. Ricaud, S. Massart, A. Piacentini, J.-P. Cammas, N. J. Livesey, H. C. Pumphrey, and D. P. Edwards (2010), A linear CO chemistry parameterization in a chemistry-transport model: evaluation and application to data assimilation, Atmos. Chem. Phys., 10(13), 6097–6115, doi:10.5194/acp-10-6097-2010.
This paper presents an evaluation of a new linear parameterization valid for the troposphere and the stratosphere, based on a first order approximation of the carbon monoxide (CO) continuity equation. This linear scheme (hereinafter noted LINCO) has been implemented in the 3-D Chemical Transport Model (CTM) MOCAGE (MOdele de Chimie Atmospherique Grande Echelle). First, a one and a half years of LINCO simulation has been compared to output obtained from a detailed chemical scheme output. The mean differences between both schemes are about +/- 25 ppbv (part per billion by volume) or 15% in the troposphere and +/- 10 ppbv or 100% in the stratosphere. Second, LINCO has been compared to diverse observations from satellite instruments covering the troposphere (Measurements Of Pollution In The Troposphere: MOPITT) and the stratosphere (Microwave Limb Sounder: MLS) and also from aircraft (Measurements of ozone and water vapour by Airbus in-service aircraft: MOZAIC programme) mostly flying in the upper troposphere and lower stratosphere (UTLS). In the troposphere, the LINCO seasonal variations as well as the vertical and horizontal distributions are quite close to MOPITT CO observations. However, a bias of similar to -40 ppbv is observed at 700 hPa between LINCO and MOPITT. In the stratosphere, MLS and LINCO present similar large-scale patterns, except over the poles where the CO concentration is underestimated by the model. In the UTLS, LINCO presents small biases less than 2% compared to independent MOZAIC profiles. Third, we assimilated MOPITT CO using a variational 3D-FGAT (First Guess at Appropriate Time) method in conjunction with MOCAGE for a long run of one and a half years. The data assimilation greatly improves the vertical CO distribution in the troposphere from 700 to 350 hPa compared to independent MOZAIC profiles. At 146 hPa, the assimilated CO distribution is also improved compared to MLS observations by reducing the bias up to a factor of 2 in the tropics. This study confirms that the linear scheme is able to simulate reasonably well the CO distribution in the troposphere and in the lower stratosphere. Therefore, the low computing cost of the linear scheme opens new perspectives to make free runs and CO data assimilation runs at high resolution and over periods of several years.
Deeter, M. N., D. P. Edwards, J. C. Gille, L. K. Emmons, G. Francis, S.-P. Ho, D. Mao, D. Masters, H. Worden, J. R. Drummond, and P. C. Novelli (2010), The MOPITT version 4 CO product: Algorithm enhancements, validation, and  long-term stability, J. Geophys. Res.-Atmos., 115(D7), doi:10.1029/2009JD013005. [online] Available from: .
Vertical profiles of carbon monoxide (CO) concentration and corresponding total column values derived from measurements made by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument are now being processed operationally with the “version 4” (V4) retrieval algorithm. This algorithm exploits the results of analyses of in situ data, chemical transport modeling, and radiative transfer modeling in the MOPITT postlaunch era. Improvements in the V4 product are evident in both clean and polluted conditions. The new products are validated using CO in situ measurements acquired from aircraft from 2000 to 2007. As determined by both retrieval simulations and observations, retrieval bias drift is typically about 1 ppbv/yr for levels in the middle troposphere and about 2 ppbv/yr in the upper troposphere. Retrieval simulations indicate that observed bias drift may be the result of gradual on-orbit changes in the instrument’s modulation cell parameters.
Emmons, L. K., S. Walters, P. G. Hess, J.-F. Lamarque, G. G. Pfister, D. Fillmore, C. Granier, A. Guenther, D. Kinnison, T. Laepple, J. Orlando, X. Tie, G. Tyndall, C. Wiedinmyer, S. L. Baughcum, and S. Kloster (2010), Description and evaluation of the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4), Geoscientific Model Development, 3(1), 43–67, doi:10.5194/gmd-3-43-2010.
The Model for Ozone and Related chemical Tracers, version 4 (MOZART-4) is an offline global chemical transport model particularly suited for studies of the troposphere. The updates of the model from its previous version MOZART-2 are described, including an expansion of the chemical mechanism to include more detailed hydrocarbon chemistry and bulk aerosols. Online calculations of a number of processes, such as dry deposition, emissions of isoprene and monoterpenes and photolysis frequencies, are now included. Results from an eight-year simulation (2000–2007) are presented and evaluated. The MOZART-4 source code and standard input files are available for download from the NCAR Community Data Portal (
Jacob, D. J., J. H. Crawford, H. Maring, A. D. Clarke, J. E. Dibb, L. K. Emmons, R. A. Ferrare, C. A. Hostetler, P. B. Russell, H. B. Singh, A. M. Thompson, G. E. Shaw, E. McCauley, J. R. Pederson, and J. A. Fisher (2010), The Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission: design, execution, and first results, Atmos. Chem. Phys., 10(11), 5191–5212, doi:10.5194/acp-10-5191-2010.
The NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission was conducted in two 3-week deployments based in Alaska (April 2008) and western Canada (June–July 2008). Its goal was to better understand the factors driving current changes in Arctic atmospheric composition and climate, including (1) influx of mid-latitude pollution, (2) boreal forest fires, (3) aerosol radiative forcing, and (4) chemical processes. The June–July deployment was preceded by one week of flights over California (ARCTAS-CARB) focused on (1) improving state emission inventories for greenhouse gases and aerosols, (2) providing observations to test and improve models of ozone and aerosol pollution. ARCTAS involved three aircraft: a DC-8 with a detailed chemical payload, a P-3 with an extensive aerosol and radiometric payload, and a B-200 with aerosol remote sensing instrumentation. The aircraft data augmented satellite observations of Arctic atmospheric composition, in particular from the NASA A-Train. The spring phase (ARCTAS-A) revealed pervasive Asian pollution throughout the Arctic as well as significant European pollution below 2 km. Unusually large Siberian fires in April 2008 caused high concentrations of carbonaceous aerosols and also affected ozone. Satellite observations of BrO column hotspots were found not to be related to Arctic boundary layer events but instead to tropopause depressions, suggesting the presence of elevated inorganic bromine (5–10 pptv) in the lower stratosphere. Fresh fire plumes from Canada and California sampled during the summer phase (ARCTAS-B) indicated low NOx emission factors from the fires, rapid conversion of NOx to PAN, no significant secondary aerosol production, and no significant ozone enhancements except when mixed with urban pollution.
Kar, J., M. N. Deeter, J. Fishman, Z. Liu, A. Omar, J. K. Creilson, C. R. Trepte, M. A. Vaughan, and D. M. Winker (2010), Wintertime pollution over the Eastern Indo-Gangetic Plains as observed from MOPITT, CALIPSO and tropospheric ozone residual data, Atmos. Chem. Phys., 10(24), 12273–12283, doi:10.5194/acp-10-12273-2010.
A large wintertime increase in pollutants has been observed over the eastern parts of the Indo Gangetic Plains. We use improved version 4 carbon monoxide (CO) retrievals from the Measurements of Pollution in the Troposphere (MOPITT) along with latest version 3 aerosol data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar instrument and the tropospheric ozone residual products to characterize this pollution pool. The feature is seen primarily in the lower troposphere from about November to February with strong concomitant increases in CO and aerosol optical depth (AOD). The signature of the feature is also observed in tropospheric ozone column data. The height resolved aerosol data from CALIPSO confirm the trapping of the pollution pool at the lowest altitudes. The observations indicate that MOPITT can capture this low altitude phenomenon even in winter conditions as indicated by the averaging kernels.
Kopacz, M., D. J. Jacob, J. A. Fisher, J. A. Logan, L. Zhang, I. A. Megretskaia, R. M. Yantosca, K. Singh, D. K. Henze, J. P. Burrows, M. Buchwitz, I. Khlystova, W. W. McMillan, J. C. Gille, D. P. Edwards, A. Eldering, V. Thouret, and P. Nedelec (2010), Global estimates of CO sources with high resolution by adjoint inversion of multiple satellite datasets (MOPITT, AIRS, SCIAMACHY, TES), Atmos. Chem. Phys., 10(3), 855–876, doi:10.5194/acp-10-855-2010.
We combine CO column measurements from the MOPITT, AIRS, SCIAMACHY, and TES satellite instruments in a full-year (May 2004-April 2005) global inversion of CO sources at 4°×5° spatial resolution and monthly temporal resolution. The inversion uses the GEOS-Chem chemical transport model (CTM) and its adjoint applied to MOPITT, AIRS, and SCIAMACHY. Observations from TES, surface sites (NOAA/GMD), and aircraft (MOZAIC) are used for evaluation of the a posteriori solution. Using GEOS-Chem as a common intercomparison platform shows global consistency between the different satellite datasets and with the in situ data. Differences can be largely explained by different averaging kernels and a priori information. The global CO emission from combustion as constrained in the inversion is 1350 Tg a-1. This is much higher than current bottom-up emission inventories. A large fraction of the correction results from a seasonal underestimate of CO sources at northern mid-latitudes in winter and suggests a larger-than-expected CO source from vehicle cold starts and residential heating. Implementing this seasonal variation of emissions solves the long-standing problem of models underestimating CO in the northern extratropics in winter-spring. A posteriori emissions also indicate a general underestimation of biomass burning in the GFED2 inventory. However, the tropical biomass burning constraints are not quantitatively consistent across the different datasets.
Mieville, A., C. Granier, C. Liousse, B. Guillaume, F. Mouillot, J.-F. Lamarque, J.-M. Grégoire, and G. Pétron (2010), Emissions of gases and particles from biomass burning during the 20th century using satellite data and an historical reconstruction, Atmospheric Environment, 44(11), 1469–1477, doi:10.1016/j.atmosenv.2010.01.011.
A new dataset of emissions of trace gases and particles resulting from biomass burning has been developed for the historical and the recent period (1900–2005). The purpose of this work is to provide a consistent gridded emissions dataset of atmospheric chemical species from 1900 to 2005 for chemistry-climate simulations. The inventory is built in two steps. First, fire emissions are estimated for the recent period (1997–2005) using satellite products (GBA2000 burnt areas and ATSR fire hotspots); the temporal and spatial distribution of the CO2 emissions for the 1997–2005 period is estimated through a calibration of ATSR fire hotspots. The historical inventory, covering the 1900–2000 period on a decadal basis, is derived from the historical reconstruction of burned areas from Mouillot and Field (2005). The historical emissions estimates are forced, for each main ecosystem, to agree with the recent inventory estimates, ensuring consistency between past and recent emissions. The methodology used for estimating the fire emissions is discussed, together with the time evolution of biomass burning emissions during the 20th century, first at the global scale and then for specific regions. The results are compared with the distributions provided by other inventories and results of inverse modeling studies.
Pfister, G. G., L. K. Emmons, D. P. Edwards, A. Arellano, G Sachse, and T. Campos (2010), Variability of springtime transpacific pollution transport during 2000–2006: the INTEX-B mission in the context of previous years, Atmos. Chem. Phys., 10(3), 1345–1359, doi:10.5194/acp-10-1345-2010.
We analyze the transport of pollution across the Pacific during the NASA INTEX-B (Intercontinental Chemical Transport Experiment Part B) campaign in spring 2006 and examine how this year compares to the time period for 2000 through 2006. In addition to aircraft measurements of carbon monoxide (CO) collected during INTEX-B, we include in this study multi-year satellite retrievals of CO from the Measurements of Pollution in the Troposphere (MOPITT) instrument and simulations from the chemistry transport model MOZART-4. Model tracers are used to examine the contributions of different source regions and source types to pollution levels over the Pacific. Additional modeling studies are performed to separate the impacts of inter-annual variability in meteorology and dynamics from changes in source strength. Interannual variability in the tropospheric CO burden over the Pacific and the US as estimated from the MOPITT data range up to 7% and a somewhat smaller estimate (5%) is derived from the model. When keeping the emissions in the model constant between years, the year-to-year changes are reduced (2%), but show that in addition to changes in emissions, variable meteorological conditions also impact transpacific pollution transport. We estimate that about 1/3 of the variability in the tropospheric CO loading over the contiguous US is explained by changes in emissions and about 2/3 by changes in meteorology and transport. Biomass burning sources are found to be a larger driver for inter-annual variability in the CO loading compared to fossil and biofuel sources or photochemical CO production even though their absolute contributions are smaller. Source contribution analysis shows that the aircraft sampling during INTEX-B was fairly representative of the larger scale region, but with a slight bias towards higher influence from Asian contributions.
Worden, H. M., M. N. Deeter, D. P. Edwards, J. C. Gille, J. R. Drummond, and P. Nédélec (2010), Observations of near-surface carbon monoxide from space using MOPITT multispectral retrievals, Journal of Geophysical Research (Atmospheres), 115(d14), 18314, doi:10.1029/2010JD014242.
Using both thermal infrared (TIR) and near infrared (NIR) channels of MOPITT (Measurements of Pollution in the Troposphere) on EOS-Terra, we demonstrate the first coincident multispectral retrievals of carbon monoxide (CO) from space. Exploiting both TIR and NIR channels has been possible due to recent progress in characterizing NIR channel radiance errors. This has allowed us to trade off sensitivity to near surface CO for larger random errors in the combined retrieval. By examining retrieval diagnostics such as DFS (degrees of freedom for signal) and averaging kernels for the multispectral retrieval (TIR + NIR) as compared to the TIR-only retrieval, we find that adding the NIR channel to the retrieval significantly increases sensitivity to CO, especially near the surface, but with high spatial variability due to surface albedo variations. The cases with the largest increases in DFS are over regions with low thermal contrast between the surface and lower atmosphere. In the tropics (23.4°S-23.4°N), the fraction of daytime land cases with at least 0.4 DFS in the surface layer (surface to 800 hPa) is 20% for TIR-only retrievals compared to 59% for multispectral retrievals. Vertical resolution for the surface layer is also improved, in some cases from around 6 km for TIR-only to roughly 1 km for TIR + NIR. Since we apply a single a priori CO profile (unlike MOPITT V4) and error covariance in all the retrievals reported here, these increases are due solely to the addition of the NIR channel. Enhanced sensitivity to near surface CO is especially evident in a case study for central/east Asia where source regions for urban areas with high population density are clearly identifiable. Although these retrievals are still a research product and require further validation and scientific evaluation, they demonstrate the increased sensitivity to CO in the lowermost troposphere that can be obtained from multispectral MOPITT data.
Zhang, Y., S. C. Olsen, and M. K. Dubey (2010), WRF/Chem simulated springtime impact of rising Asian emissions on air quality over the U.S., Atmospheric Environment, 44(24), 2799–2812, doi:10.1016/j.atmosenv.2010.05.003.
This paper examines the impact of tripled anthropogenic emissions from China and India over the base level (gaseous species and carbonaceous aerosols for 2000) on air quality over the U.S. using the WRF/Chem (Weather Research and Forecasting – Chemistry) model at 1° resolution. WRF/Chem is a state-of-the-science, fully coupled chemistry and meteorology system suitable for simulating the transport and dispersion of pollutants and their impacts. The analyses in this work were focused on MAM (March, April and May). The simulations indicate an extensive area of elevated pollutant concentrations spanning from the Arabian Sea to the Northern Pacific and to the Northern Atlantic. MAM mean contributions from the tripled Asian emissions over the U.S. are found to be: 6–12 ppbv for CO, 1.0–2.5 ppbv for O3, and 0.6–1.6 μg m−3 for PM2.5 on a daily basis.


Bowman, K. W., D. B. A. Jones, J. A. Logan, H. Worden, F. Boersma, R. Chang, S. Kulawik, G. Osterman, P. Hamer, and J. Worden (2009), The zonal structure of tropical O3 and CO as observed by the Tropospheric Emission Spectrometer in November 2004 – Part 2: Impact of surface emissions  on O3 and its precursors, Atmos. Chem. Phys., 9(11), 3563–3582, doi:10.5194/acp-9-3563-2009.
The impact of surface emissions on the zonal structure of tropical tropospheric ozone and carbon monoxide is investigated for November 2004 using satellite observations, in-situ measurements, and chemical transport models in conjunction with inverse-estimated surface emissions.Vertical ozone profiles from the Tropospheric Emission Spectrometer (TES) and ozone sonde measurements from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network show elevated concentrations of ozone over Indonesia and Australia (60-70 ppb) in the lower troposphere against the backdrop of the well-known zonal ”wave-one” pattern with ozone concentrations of (70-80 ppb) centered over the Atlantic . Observational evidence from TES CO vertical profiles and Ozone Monitoring Instrument (OMI) NO2 columns point to regional surface emissions as an important contributor to the elevated ozone over Indonesia. This contribution is investigated with the GEOS-Chem chemistry and transport model using surface emission estimates derived from an optimal inverse model, which was constrained by TES and Measurements Of Pollution In The Troposphere (MOPITT) CO profiles (Jones et al., 2009). These a posteriori estimates, which were over a factor of 2 greater than climatological emissions, reduced differences between GEOS-Chem and TES ozone observations by 30-40% over Indonesia. The response of the free tropospheric chemical state to the changes in these emissions is investigated for ozone, CO, NOx, and PAN. Model simulations indicate that ozone over Indonesian/Australian is sensitive to regional changes in surface emissions of NOx but relatively insensitive to lightning NOx. Over sub-equatorial Africa and South America, free tropospheric NOx was reduced in response to increased surface emissions potentially muting ozone production.
Deeter, M. N., D. P. Edwards, J. C. Gille, and J. R. Drummond (2009), CO retrievals based on MOPITT near-infrared observations, Journal of Geophysical Research (Atmospheres), 114(d13), 4303, doi:10.1029/2008JD010872.
We report the first retrieval results of tropospheric carbon monoxide (CO) exclusively using near-infrared (NIR) radiances in the 2.3 μm CO overtone band observed by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument. For daytime overpasses over land, such observations complement MOPITT’s thermal infrared (TIR) observations in the 4.7 μm CO fundamental band, especially for constraining the CO total column. Retrievals are performed in an optimal estimation framework in which effective radiance errors due to geophysical sources are estimated empirically. The new NIR-based retrievals are evaluated through comparisons with both the standard TIR-based MOPITT CO product and CO profile measurements.
Edwards, D. P., A. F. Arellano, and M. N. Deeter (2009), A satellite observation system simulation experiment for carbon monoxide  in the lowermost troposphere, J. Geophys. Res.-Atmos., 114, doi:10.1029/2008JD011375.
We demonstrate the feasibility of using observing system simulation experiment (OSSE) studies to help define quantitative trace gas measurement requirements for satellite missions and to evaluate the expected performance of proposed observing strategies. The 2007 U. S. National Research Council Decadal Survey calls for a geostationary (GEO) satellite mission for atmospheric composition and air quality applications (Geostationary Coastal and Air Pollution Events Mission (GEO-CAPE)). The requirement includes a multispectral (near-infrared and thermal infrared) measurement of carbon monoxide (CO) at high spatiotemporal resolution with information on lowermost troposphere concentration. We present an OSSE to assess the improvement in surface CO characterization that would result from the addition of a GEO-CAPE CO measurement to current low Earth orbit (LEO) thermal infrared-only measurements. We construct instrument simulators for these two measurement scenarios and study the case of July 2004 when wildfires in Alaska and Canada led to significant CO pollution over the contiguous United States. Compared to a control experiment, an ensemble-based data assimilation of simulated satellite observations in a global model leads to improvements in both the surface CO distributions and the time evolution of CO profiles at locations affected by wildfire plumes and by urban emissions. In all cases, an experiment with the GEO-CAPE CO measurement scenario (overall model skill of 0.84) performed considerably better than the experiment with the current LEO/thermal infrared measurement (skill of 0.58) and the control (skill of 0.07). This demonstrates the advantages of increased sampling from GEO and enhanced measurement sensitivity to the lowermost troposphere with a multispectral retrieval.
Emmons, L. K., D. P. Edwards, M. N. Deeter, J. C. Gille, T. Campos, P. Nédélec, P. Novelli, and G. Sachse (2009), Measurements of Pollution In The Troposphere (MOPITT) validation through 2006, Atmos. Chem. Phys., 9(5), 1795–1803, doi:10.5194/acp-9-1795-2009.
Comparisons of aircraft measurements of carbon monoxide (CO) to the retrievals of CO using observations from the Measurements of Pollution in The Troposphere (MOPITT) instrument onboard the Terra satellite are presented. Observations made as part of the NASA INTEX-B and NSF MIRAGE field campaigns during March-May 2006 are used to validate the MOPITT CO retrievals, along with routine samples from 2001 through 2006 from NOAA and the MOZAIC measurements from commercial aircraft. A significant positive bias, around 20% for total column CO, in MOPITT CO was found in the comparison to in situ measurements during 2006. Comparisons to the long-term records of measurements from NOAA and MOZAIC revealed an increasing bias in the V3 MOPITT CO retrievals over time. The impact of an instrumental drift is illustrated through retrieval simulations.
George, M., C. Clerbaux, D. Hurtmans, S. Turquety, P.-F. Coheur, M. Pommier, J. Hadji-Lazaro, D. P. Edwards, H. Worden, M. Luo, C. Rinsland, and W. McMillan (2009), Carbon monoxide distributions from the IASI/METOP mission: evaluation with other space-borne remote sensors, Atmos. Chem. Phys., 9(21), 8317–8330, doi:10.5194/acp-9-8317-2009.
The Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp satellite measures carbon monoxide (CO) on a global scale, twice a day. CO total columns and vertical profiles are retrieved in near real time from the nadir radiance spectra measured by the instrument in the thermal infrared (TIR) spectral range. This paper describes the measurement vertical sensitivity and provides a first assessment of the capabilities of IASI to measure CO distributions. On the global scale, 0.8 to 2.4 independent pieces of information are available for the retrieval. At mid latitudes, the information ranges between 1.5 and 2, which enables the lower and upper troposphere to be distinguished, especially when thermal contrast is significant. Global distributions of column CO are evaluated with correlative observations available from other nadir looking TIR missions currently in operation: the Measurements of Pollution in the Troposphere (MOPITT) onboard TERRA, the Atmospheric Infrared Sounder (AIRS) onboard AQUA and the Tropospheric Emission Spectrometer (TES) onboard AURA. The IASI CO columns are compared with MOPITT, AIRS and TES CO columns, adjusted with the a priori, for three different months: August 2008, November 2008 and February 2009. On average, total column discrepancies of about 7% are found between IASI and the three other sounders in the Northern Hemisphere and in the equatorial region. However when strong CO concentrations are present, such as during fire events, these discrepancies can climb as high as 17%. Instrument specifications of IASI versus other missions are also discussed.
Ho, S.-P., D. P. Edwards, J. C. Gille, M. Luo, G. B. Osterman, S. S. Kulawik, and H. Worden (2009), A global comparison of carbon monoxide profiles and column amounts from Tropospheric Emission Spectrometer (TES) and Measurements of Pollution in the Troposphere (MOPITT), Journal of Geophysical Research: Atmospheres, 114(D21), n/a–n/a, doi:10.1029/2009JD012242.
In this study, we compare carbon monoxide (CO) products from the Measurements of Pollution in the Troposphere (MOPITT) and Tropospheric Emission Spectrometer (TES) and investigate the possible causes of the differences between retrievals for these two data sets. Direct comparisons of CO retrievals for July 2006 show that TES CO concentrations are consistently biased lower than those of MOPITT by 25 ppbv near the surface and by 20 ppbv at 150 hPa, primarily due to different a priori profiles and covariance matrices used in the TES and MOPITT CO retrievals. To reduce the effects of different a priori constraints, we apply TES a priori profiles and covariance matrices to a modified MOPITT retrieval algorithm. The mean TES-MOPITT CO difference decreases from −25 to −10 ppbv near the surface. To further account for retrieval smoothing errors due to different TES and MOPITT averaging kernels, TES averaging kernels are used to smooth MOPITT CO profiles to derive TES-equivalent CO profiles. Compared to these, TES CO profiles are biased 1 ppbv lower near the surface and 4–9 ppbv lower in the troposphere, and the mean absolute TES and TES-equivalent CO column difference is less than 6.5%. The mean TES and MOPITT CO differences due to smoothing errors are close to zero, and the remaining bias is primarily due to the combined effects of radiance biases, forward model errors, and the spatial and temporal mismatches of TES and MOPITT pixels.


Clerbaux, C., D. P. Edwards, M. Deeter, L. Emmons, J.-F. Lamarque, X. X. Tie, S. T. Massie, and J. Gille (2008a), Carbon monoxide pollution from cities and urban areas observed by the Terra/MOPITT mission, Geophysical Research Letters, 35(3), n/a–n/a, doi:10.1029/2007GL032300.
Carbon monoxide (CO) is a key species for tracking pollution plumes. The Measurement Of Pollution in The Troposphere (MOPITT) mission onboard the Terra satellite has already provided 7.5 years of CO atmospheric concentration measurements around the globe. Limited sensitivity to the boundary layer is well known to be a weakness of nadir looking thermal infrared sounders. This paper investigates the possibility of using the MOPITT surface measurements to detect CO emitted by cities and urban centers. By selecting the data and averaging them over long time periods, we demonstrate that the CO pollution arising from the large cities and urban areas can be distinguished from the background transported pollution. The more favorable observations are obtained during daytime and at locations where the thermal contrast (temperature gradient) between the surface and lower atmosphere is significant.
Clerbaux, C., M. George, S. Turquety, K. A. Walker, B. Barret, P. Bernath, C. Boone, T. Borsdorff, J. P. Cammas, V. Catoire, M. Coffey, P.-F. Coheur, M. Deeter, M. De Mazière, J. Drummond, P. Duchatelet, E. Dupuy, R. de Zafra, F. Eddounia, D. P. Edwards, L. Emmons, B. Funke, J. Gille, D. W. T. Griffith, J. Hannigan, F. Hase, M. Höpfner, N. Jones, A. Kagawa, Y. Kasai, I. Kramer, E. Le Flochmoën, N. J. Livesey, M. López-Puertas, M. Luo, E. Mahieu, D. Murtagh, P. Nédélec, A. Pazmino, H. Pumphrey, P. Ricaud, C. P. Rinsland, C. Robert, M. Schneider, C. Senten, G. Stiller, A. Strandberg, K. Strong, R. Sussmann, V. Thouret, J. Urban, and A. Wiacek (2008b), CO measurements from the ACE-FTS satellite instrument: data analysis and validation using ground-based, airborne and spaceborne observations, Atmos. Chem. Phys., 8(9), 2569–2594, doi:10.5194/acp-8-2569-2008.
The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO), a good tracer of pollution plumes and atmospheric dynamics, is one of the key species provided by the primary instrument, the ACE-Fourier Transform Spectrometer (ACE-FTS). This instrument performs measurements in both the CO 1-0 and 2-0 ro-vibrational bands, from which vertically resolved CO concentration profiles are retrieved, from the mid-troposphere to the thermosphere. This paper presents an updated description of the ACE-FTS version 2.2 CO data product, along with a comprehensive validation of these profiles using available observations (February 2004 to December 2006). We have compared the CO partial columns with ground-based measurements using Fourier transform infrared spectroscopy and millimeter wave radiometry, and the volume mixing ratio profiles with airborne (both high-altitude balloon flight and airplane) observations. CO satellite observations provided by nadir-looking instruments (MOPITT and TES) as well as limb-viewing remote sensors (MIPAS, SMR and MLS) were also compared with the ACE-FTS CO products. We show that the ACE-FTS measurements provide CO profiles with small retrieval errors (better than 5% from the upper troposphere to 40 km, and better than 10% above). These observations agree well with the correlative measurements, considering the rather loose coincidence criteria in some cases. Based on the validation exercise we assess the following uncertainties to the ACE-FTS measurement data: better than 15% in the upper troposphere (8–12 km), than 30% in the lower stratosphere (12–30 km), and than 25% from 30 to 100 km.
Kar, J., D. B. A. Jones, J. R. Drummond, J. L. Attié, J. Liu, J. Zou, F. Nichitiu, M. D. Seymour, D. P. Edwards, M. N. Deeter, J. C. Gille, and A. Richter (2008), Measurement of low-altitude CO over the Indian subcontinent by MOPITT, Journal of Geophysical Research (Atmospheres), 113(d12), 16307, doi:10.1029/2007JD009362.
We show that the dayside MOPITT retrievals in the lower troposphere can provide useful information on surface sources of atmospheric CO over the Indian subcontinent. We find that MOPITT retrievals at 850 hPa show localized enhancements over the Indian subcontinent, which correlate with similar enhancements seen in the tropospheric NO2 columns from the SCIAMACHY instrument. In particular, high concentrations of CO over the Indo-Gangetic basin and some prominent cities are captured in the lower-tropospheric retrievals in spring. MOPITT averaging kernels (normalized to take into account the absorber amounts in the layers) indicate that the retrievals are sensitive to CO in the lower troposphere. In winter, MOPITT retrievals at 850 hPa can detect the strongest source areas over the eastern states of Bihar and West Bengal, thus confirming the so-called “Bihar pollution pool,” which was detected earlier in the aerosol measurements by the multiangle imaging spectroradiometer (MISR) aboard Terra. The pollution features are consistent with the spatial distribution of CO emissions in India, as reflected in the GEOS-Chem simulation of CO. Furthermore, these lower-tropospheric features in the simulation are still present after smoothing the modeled fields using the MOPITT averaging kernels and a priori profile, demonstrating that the retrievals do have sensitivity in the lower troposphere. This work indicates that although MOPITT retrievals are often most sensitive to CO in the middle and upper troposphere, they do provide information on lower-tropospheric CO in selected continental regions with strong thermal contrast and could be useful for pollution studies.
Turquety, S., C. Clerbaux, K. Law, P.-F. Coheur, A. Cozic, S. Szopa, D. A. Hauglustaine, J. Hadji-Lazaro, A. M. S. Gloudemans, H. Schrijver, C. D. Boone, P. F. Bernath, and D. P. Edwards (2008), CO emission and export from Asia: an analysis combining complementary satellite measurements (MOPITT, SCIAMACHY and ACE-FTS) with global modeling, Atmos. Chem. Phys., 8(17), 5187–5204, doi:10.5194/acp-8-5187-2008.
This study presents the complementary picture of the pollution outflow provided by several satellite observations of carbon monoxide (CO), based on different observation techniques. This is illustrated by an analysis of the Asian outflow during the spring of 2005, through comparisons with simulations by the LMDz-INCA global chemistry transport model. The CO observations from the MOPITT and SCIAMACHY nadir sounders, which provide vertically integrated information with excellent horizontal sampling, and from the ACE-FTS solar occultation instrument, which has limited spatial coverage but allows the retrieval of vertical profiles, are used. Combining observations from MOPITT (mainly sensitive to the free troposphere) and SCIAMACHY (sensitive to the full column) allows a qualitative evaluation of the boundary layer CO. The model tends to underestimate this residual compared to the observations, suggesting underestimated emissions, especially in eastern Asia. However, a better understanding of the consistency and possible biases between the MOPITT and SCIAMACHY CO is necessary for a quantitative evaluation. Underestimated emissions, and possibly too low lofting and underestimated chemical production in the model, lead to an underestimate of the export to the free troposphere, as highlighted by comparisons with MOPITT and ACE-FTS. Both instruments observe large trans-Pacific transport extending from ∼20° N to ∼60° N, with high upper tropospheric CO observed by ACE-FTS above the eastern Pacific (with values of up to 300 ppbv around 50° N at 500 hPa and up to ∼200 ppbv around 30° N at 300 hPa). The low vertical and horizontal resolutions of the global model do not allow the simulation of the strong enhancements in the observed plumes. However, the transport patterns are well captured, and are mainly attributed to export from eastern Asia, with increasing contributions from South Asia and Indonesia towards the tropics. Additional measurements of C2H2, C2H6 and HCN by ACE-FTS provide further information on the plume history. C2H2 and C2H6 enhancements are well correlated with the CO plumes, indicating common sources and rapid trans-Pacific transport. HCN observations show that the biomass burning contributes mainly at latitudes lower than ∼40° N. This study provides a first step towards a full combination of complementary observations, but also highlights the need for a better evaluation of consistency between the datasets in order to allow precise quantitative analyses.


Arellano, A. F., K. Raeder, J. L. Anderson, P. G. Hess, L. K. Emmons, D. P. Edwards, G. G. Pfister, T. L. Campos, and G. W. Sachse (2007), Evaluating model performance of an ensemble-based chemical data assimilation system during INTEX-B field mission, Atmos. Chem. Phys., 7(21), 5695–5710, doi:10.5194/acp-7-5695-2007.
We present a global chemical data assimilation system using a global atmosphere model, the Community Atmosphere Model (CAM3) with simplified chemistry and the Data Assimilation Research Testbed (DART) assimilation package. DART is a community software facility for assimilation studies using the ensemble Kalman filter approach. Here, we apply the assimilation system to constrain global tropospheric carbon monoxide (CO) by assimilating meteorological observations of temperature and horizontal wind velocity and satellite CO retrievals from the Measurement of Pollution in the Troposphere (MOPITT) satellite instrument. We verify the system performance using independent CO observations taken on board the NSF/NCAR C-130 and NASA DC-8 aircrafts during the April 2006 part of the Intercontinental Chemical Transport Experiment (INTEX-B). Our evaluations show that MOPITT data assimilation provides significant improvements in terms of capturing the observed CO variability relative to no MOPITT assimilation (i.e. the correlation improves from 0.62 to 0.71, significant at 99% confidence). The assimilation provides evidence of median CO loading of about 150 ppbv at 700 hPa over the NE Pacific during April 2006. This is marginally higher than the modeled CO with no MOPITT assimilation (∼140 ppbv). Our ensemble-based estimates of model uncertainty also show model overprediction over the source region (i.e. China) and underprediction over the NE Pacific, suggesting model errors that cannot be readily explained by emissions alone. These results have important implications for improving regional chemical forecasts and for inverse modeling of CO sources and further demonstrate the utility of the assimilation system in comparing non-coincident measurements, e.g. comparing satellite retrievals of CO with in-situ aircraft measurements.
Bousserez, N., J. L. Attié, V. H. Peuch, M. Michou, G. Pfister, D. Edwards, L. Emmons, C. Mari, B. Barret, S. R. Arnold, A. Heckel, A. Richter, H. Schlager, A. Lewis, M. Avery, G. Sachse, E. V. Browell, and J. W. Hair (2007), Evaluation of the MOCAGE chemistry transport model during the ICARTT/ITOP experiment, Journal of Geophysical Research: Atmospheres, 112(D10), n/a–n/a, doi:10.1029/2006JD007595.
Intercontinental Transport of Ozone and Precursors (ITOP), part of International Consortium for Atmospheric Research on Transport and Transformation (ICARTT), was a large experimental campaign designed to improve our understanding of the chemical transformations within plumes during long-range transport (LRT) of pollution from North America to Europe. This campaign took place in July and August 2004, when a strong fire season occurred in North America. Burning by-products were transported over large distances, sometimes reaching Europe. A chemical transport model, Modélisation de la Chimie Atmosphérique Grande Echelle (MOCAGE), with a high grid resolution (0.5° × 0.5°) over the North Atlantic area and a daily inventory of biomass burning emissions over the United States, has been used to simulate the period. By comparing our results with available aircraft in situ measurements and satellite data (MOPITT CO and SCIAMACHY NO2), we show that MOCAGE is capable of representing the main characteristics of the tropospheric ozone-NOx-hydrocarbon chemistry during the ITOP experiment. In particular, high resolution allows the accurate representation of the pathway of exported pollution over the Atlantic, where plumes were transported preferentially at 6 km altitude. The model overestimates OH mixing ratios up to a factor of 2 in the lower troposphere, which results in a global overestimation of hydrocarbons oxidation by-products (PAN and ketones) and an excess of O3 (30–50 ppbv) in the planetary boundary layer (PBL) over the continental United States. Sensitivity study revealed that lightning NO emissions contributed significantly to the NOx budget in the upper troposphere of northeast America during the summer 2004.
Deeter, M. N., D. P. Edwards, and J. C. Gille (2007a), Retrievals of carbon monoxide profiles from MOPITT observations using lognormal a priori statistics, Journal of Geophysical Research: Atmospheres, 112(D11), n/a–n/a, doi:10.1029/2006JD007999.
Optimal estimation methods, such as the “maximum a posteriori” solution, are commonly employed for retrieving profiles of atmospheric trace gases from satellite observations. To complement the information actually contained in the measured radiances, such methods exploit a priori information describing the gases’ variability characteristics. We show that in situ surface-based data sets for carbon monoxide (CO) volume mixing ratio (VMR) indicate that the variability of CO is more accurately modeled in terms of a “lognormal” probability distribution function (PDF) than a “VMR-normal” PDF. The VMR-normal PDF is particularly poor at describing CO variability in unpolluted conditions. We also compare retrievals of carbon monoxide (CO) vertical profiles based on Measurements of Pollution in the Troposphere (MOPITT) observations for 1 day using both VMR-normal and lognormal statistical models. Use of the lognormal model improves retrieval convergence and yields fewer profiles with unphysically small VMR values. Generally, these results highlight the importance of properly representing the variability of trace gas concentrations in optimal estimation-based retrieval algorithms.
Deeter, M. N., D. P. Edwards, J. C. Gille, and J. R. Drummond (2007b), Sensitivity of MOPITT observations to carbon monoxide in the lower troposphere, Journal of Geophysical Research (Atmospheres), 112(d11), 24306, doi:10.1029/2007JD008929.
The sensitivity of Measurements of Pollution in the Troposphere (MOPITT) observations to carbon monoxide (CO) concentrations in the lower troposphere (LT) varies widely as the result of variability in thermal contrast conditions. This effect is evident in both the MOPITT weighting functions and averaging kernels, particularly after these quantities are properly normalized to remove grid effects. Comparisons of simulated weighting functions and averaging kernels with operational data confirm the significance of thermal contrast effects. Retrieval sensitivity to LT CO is greatest in daytime observations over land, particularly in tropical and midlatitude regions exhibiting large diurnal variations in surface temperature. Nighttime observations over land typically exhibit poor sensitivity to LT CO. On the global scale, analysis of MOPITT averaging kernels for 1 month indicates that daytime MOPITT observations offer useful sensitivity to LT CO over large areas of most continents. Exceptions include tropical rainforests in Africa and South America, where thermal contrast conditions are relatively weak.
Emmons, L. K., G. G. Pfister, D. P. Edwards, J. C. Gille, G. Sachse, D. Blake, S. Wofsy, C. Gerbig, D. Matross, and P. Nédélec (2007), Measurements of Pollution in the Troposphere (MOPITT) validation exercises during summer 2004 field campaigns over North America, Journal of Geophysical Research: Atmospheres, 112(D12), n/a–n/a, doi:10.1029/2006JD007833.
Measurements of carbon monoxide (CO) made as part of three aircraft experiments during the summer of 2004 over North America have been used for the continued validation of the CO retrievals from the Measurements of Pollution in the Troposphere (MOPITT) instrument on board the Terra satellite. Vertical profiles measured during the NASA INTEX-A campaign, designed to be coincident with MOPITT overpasses, as well as measurements made during the COBRA-2004 and MOZAIC experiments, provided valuable validation comparisons. On average, the MOPITT CO retrievals are biased slightly high for these North America locations. While the mean bias differs between the different aircraft experiments (e.g., 7.0 ppbv for MOZAIC to 18.4 ppbv for COBRA at 700 hPa), the standard deviations are quite large, so the results for the three data sets can be considered consistent. On average, it is estimated that MOPITT is 7–14% high at 700 hPa and ∼3% high at 350 hPa. These results are consistent with the validation results for the Carr, Colorado, Harvard Forest, Massachusetts, and Poker Flats, Alaska, aircraft profiles for “phase 2” presented by Emmons et al. (2004) and are generally within the design criteria of 10% accuracy.
Liang, Q., L. Jaeglé, R. C. Hudman, S. Turquety, D. J. Jacob, M. A. Avery, E. V. Browell, G. W. Sachse, D. R. Blake, W. Brune, X. Ren, R. C. Cohen, J. E. Dibb, A. Fried, H. Fuelberg, M. Porter, B. G. Heikes, G. Huey, H. B. Singh, and P. O. Wennberg (2007), Summertime influence of Asian pollution in the free troposphere over North America, Journal of Geophysical Research: Atmospheres, 112(D12), n/a–n/a, doi:10.1029/2006JD007919.
We analyze aircraft observations obtained during INTEX-A (1 July to 14 August 2004) to examine the summertime influence of Asian pollution in the free troposphere over North America. By applying correlation analysis and principal component analysis (PCA) to the observations between 6 and 12 km, we find dominant influences from recent convection and lightning (13% of observations), Asia (7%), the lower stratosphere (7%), and boreal forest fires (2%), with the remaining 71% assigned to background. Asian air masses are marked by high levels of CO, O3, HCN, PAN, C2H2, C6H6, methanol, and SO42–. The partitioning of NOy species in the Asian plumes is dominated by PAN (∼600 pptv), with varying NOx/HNO3 ratios in individual plumes, consistent with individual transit times of 3–9 days. Export of Asian pollution occurred in warm conveyor belts of midlatitude cyclones, deep convection, and in typhoons. Compared to Asian outflow measurements during spring, INTEX-A observations display lower levels of anthropogenic pollutants (CO, C3H8, C2H6, C6H6) due to shorter summer lifetimes; higher levels of biogenic tracers (methanol and acetone) because of a more active biosphere; and higher levels of PAN, NOx, HNO3, and O3 reflecting active photochemistry, possibly enhanced by efficient NOy export and lightning. The high ΔO3/ΔCO ratio (0.76 mol/mol) in Asian plumes during INTEX-A is due to strong photochemical production and, in some cases, mixing with stratospheric air along isentropic surfaces. The GEOS-Chem global model captures the timing and location of the Asian plumes. However, it significantly underestimates the magnitude of observed enhancements in CO, O3, PAN and NOx.
Luo, M., C. P. Rinsland, C. D. Rodgers, J. A. Logan, H. Worden, S. Kulawik, A. Eldering, A. Goldman, M. W. Shephard, M. Gunson, and M. Lampel (2007), Comparison of carbon monoxide measurements by TES and MOPITT: Influence of a priori data and instrument characteristics on nadir atmospheric species retrievals, Journal of Geophysical Research: Atmospheres, 112(D9), n/a–n/a, doi:10.1029/2006JD007663.
Comparisons of tropospheric carbon monoxide (CO) volume mixing ratio profiles and total columns are presented from nadir-viewing measurements made by the Tropospheric Emission Spectrometer (TES) on the NASA Aura satellite and by the Measurements of Pollution in the Troposphere (MOPITT) instrument on the NASA Terra satellite. In this paper, we first explore the factors that relate the retrieved and the true species profiles. We demonstrate that at a given location and time the retrieved species profiles reported by different satellite instrument teams can be very different from each other. We demonstrate the influence of the a priori data and instrument characteristics on the CO products from TES and MOPITT and on their comparisons. Direct comparison of TES and MOPITT retrieved CO profiles and columns show significant differences in the lower and upper troposphere. To perform a more proper and rigorous comparison between the two instrument observations we allow for different a priori profiles and averaging kernels. We compare (1) TES retrieved CO profiles adjusted to the MOPITT a priori with the MOPITT retrievals and (2) the above adjusted TES CO profiles with the MOPITT profiles vertically smoothed by the TES averaging kernels. These two steps greatly improve the agreement between the CO profiles and the columns from the two instruments. No systematic differences are found as a function of latitude in the final comparisons. These results show that knowledge of the a priori profiles, the averaging kernels, and the error covariance matrices in the standard data products provided by the instrument teams and understanding their roles in the retrieval products are essential in quantitatively interpreting both retrieved profiles and the derived total or partial columns for scientific applications.
Peng, L., C. Zhao, Y. Lin, X. Zheng, X. Tie, and L.-Y. Chan (2007), Analysis of carbon monoxide budget in North China, Chemosphere, 66(8), 1383–1389, doi:10.1016/j.chemosphere.2006.09.055.
A global chemical transport model (MOZART-2; model of ozone and related tracers, version 2) was used to assess physical and chemical processes that control the budget of tropospheric carbon monoxide (CO) in North China. Satellite observations of CO from the measurements of pollution in the troposphere (MOPITT) instrument are combined with model results for the analysis. The comparison between the model simulations and the satellite observations of total column CO (TCO) shows that the model can reproduce the spatial and temporal distributions. However, the model results underestimate TCO by 23% in North China. This underestimation of TCO may be caused by the uncertainties of emissions. The tropospheric CO budget analysis suggests that in North China, surface emission is the largest source of tropospheric CO. The main sinks of tropospheric CO in this region are chemical reaction and stratosphere_and_troposphere exchange. The analysis also shows that most of inflow CO to Pacific regions comes from the upwind regions of North China. This transport of CO is significant during Winter and Spring time.
Turquety, S., J. A. Logan, D. J. Jacob, R. C. Hudman, F. Y. Leung, C. L. Heald, R. M. Yantosca, S. Wu, L. K. Emmons, D. P. Edwards, and G. W. Sachse (2007), Inventory of boreal fire emissions for North America in 2004: Importance of peat burning and pyroconvective injection, Journal of Geophysical Research: Atmospheres, 112(D12), n/a–n/a, doi:10.1029/2006JD007281.
The summer of 2004 was one of the largest fire seasons on record for Alaska and western Canada. We construct a daily bottom-up fire emission inventory for that season, including consideration of peat burning and high-altitude (buoyant) injection, and evaluate it in a global chemical transport model (the GEOS-Chem CTM) simulation of CO through comparison with MOPITT satellite and ICARTT aircraft observations. The inventory is constructed by combining daily area burned reports and MODIS fire hot spots with estimates of fuel consumption and emission factors based on ecosystem type. We estimate the contribution from peat burning using drainage and peat distribution maps for Alaska and Canada; 17% of the reported 5.1 × 106 ha burned were located in peatlands in 2004. Our total estimate of North American fire emissions during the summer of 2004 is 30 Tg CO, including 11 Tg from peat. Including peat burning in the GEOS-Chem simulation improves agreement with MOPITT observations. The long-range transport of fire plumes observed by MOPITT suggests that the largest fires injected a significant fraction of their emissions in the upper troposphere.
Zhao, C., L. Peng, X. Tie, Y. Lin, C. Li, X. Zheng, and Y. Fang (2007), A High CO Episode of Long-Range Transport Detected by MOPITT, Water Air Soil Pollut, 178(1–4), 207–216, doi:10.1007/s11270-006-9191-1.
Recent developments in satellite remote sensing technologies resulted in the ability to observe major pollution events such as dust and smoke around the world on a daily basis. Satellite imagery can sometimes detect long-range transport episodes. In this paper, a high CO episode at remote GAW station, Mt. Waliguan, detected by MOPITT CO dataset during the end of April 2002, is described. CO concentrations above 600 hPa almost doubled on 27 April and CMDL surface sample measurements also observed this significant CO enhancement. Using NCEP data, satellite fire products data and backward trajectory model we suggest that this high CO episode of 27 April is not a local pollution event, but that it is due to long-range transport from active biomass burning and biofuel burning areas located in the border areas of Pakistan and India. The trajectory cluster analysis shows that the origins of 5-day backward trajectories, for air masses reaching Mt. Waliguan station, at all altitudes, mainly overlap with the fire spot locations detected by TRMM data and biofuel burning in India.


Arellano, A. F., and P. G. Hess (2006), Sensitivity of top-down estimates of CO sources to GCTM transport, Geophysical Research Letters, 33(21), n/a–n/a, doi:10.1029/2006GL027371.
Estimates of CO sources derived from inversions using satellite observations still exhibit discrepancies. Here, we conduct controlled inverse analyses to elucidate the influence of model transport on the robustness of regional CO source estimates. We utilized Model of Ozone and Related chemical Tracers global chemical transport models (GCTM) driven by National Centers for Environmental Prediction and European Centre for Medium-Range Weather Forecast reanalyses, and GEOS-Chem GCTM driven by Global Modeling and Assimilation Office assimilated meteorology to generate response functions for prescribed regional CO sources. We find that inter-model differences in CO due to differences in transport are within 10–30% of inter-model mean CO concentration. However, these differences can translate to regionally significant spread in source estimates. While we find that CO source estimates for East Asia and North Africa are reasonably robust, we find inconsistencies and inter-model spread of greater than 40% in our source estimates for Indonesia, South America, Europe and Russia. This indicates the need for rigorous assessment on uncertainties in top-down source estimates through model inter-comparisons and ensemble approaches.
Arellano, A. F., P. S. Kasibhatla, L. Giglio, G. R. van der Werf, J. T. Randerson, and G. J. Collatz (2006), Time-dependent inversion estimates of global biomass-burning CO emissions using Measurement of Pollution in the Troposphere (MOPITT) measurements, Journal of Geophysical Research (Atmospheres), 111(d10), 9303, doi:10.1029/2005JD006613.
We present an inverse-modeling analysis of CO emissions using column CO retrievals from the Measurement of Pollution in the Troposphere (MOPITT) instrument and a global chemical transport model (GEOS-CHEM). We first focus on the information content of MOPITT CO column retrievals in terms of constraining CO emissions associated with biomass burning and fossil fuel/biofuel use. Our analysis shows that seasonal variation of biomass-burning CO emissions in Africa, South America, and Southeast Asia can be characterized using monthly mean MOPITT CO columns. For the fossil fuel/biofuel source category the derived monthly mean emission estimates are noisy even when the error statistics are accurately known, precluding a characterization of seasonal variations of regional CO emissions for this source category. The derived estimate of CO emissions from biomass burning in southern Africa during the June-July 2000 period is significantly higher than the prior estimate (prior, 34 Tg; posterior, 13 Tg). We also estimate that emissions are higher relative to the prior estimate in northern Africa during December 2000 to January 2001 and lower relative to the prior estimate in Central America and Oceania/Indonesia during April-May and September-October 2000, respectively. While these adjustments provide better agreement of the model with MOPITT CO column fields and with independent measurements of surface CO from National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory at background sites in the Northern Hemisphere, some systematic differences between modeled and measured CO fields persist, including model overestimation of background surface CO in the Southern Hemisphere. Characterizing and accounting for underlying biases in the measurement model system are needed to improve the robustness of the top-down estimates.
Edwards, D. P., L. K. Emmons, J. C. Gille, A. Chu, J.-L. Attié, L. Giglio, S. W. Wood, J. Haywood, M. N. Deeter, S. T. Massie, D. C. Ziskin, and J. R. Drummond (2006a), Satellite-observed pollution from Southern Hemisphere biomass burning, Journal of Geophysical Research: Atmospheres, 111(D14), 14312, doi:10.1029/2005JD006655.
Biomass burning is a major source of pollution in the tropical Southern Hemisphere, and fine mode carbonaceous particles are produced by the same combustion processes that emit carbon monoxide (CO). In this paper we examine these emissions with data from the Terra satellite, CO profiles from the Measurement of Pollution in the Troposphere (MOPITT) instrument, and fine-mode aerosol optical depth (AOD) from the Moderate-Resolution Imaging Spectroradiometer (MODIS). The satellite measurements are used in conjunction with calculations from the MOZART chemical transport model to examine the 2003 Southern Hemisphere burning season with particular emphasis on the months of peak fire activity in September and October. Pollutant emissions follow the occurrence of dry season fires, and the temporal variation and spatial distributions of MOPITT CO and MODIS AOD are similar. We examine the outflow from Africa and South America with emphasis on the impact of these emissions on clean remote regions. We present comparisons of MOPITT observations and ground-based interferometer data from Lauder, New Zealand, which indicate that intercontinental transport of biomass burning pollution from Africa often determines the local air quality. The correlation between enhancements of AOD and CO column for distinct biomass burning plumes is very good with correlation coefficients greater than 0.8. We present a method using MOPITT and MODIS data for estimating the emission ratio of aerosol number density to CO concentration which could prove useful as input to modeling studies. We also investigate decay of plumes from African fires following export into the Indian Ocean and compare the MOPITT and MODIS measurements as a way of estimating the regional aerosol lifetime. Vertical transport of biomass burning emissions is also examined using CO profile information. Low-altitude concentrations are very high close to source regions, but further downwind of the continents, vertical mixing takes place and results in more even CO vertical distributions. In regions of significant convection, particularly in the equatorial Indian Ocean, the CO mixing ratio is greater at higher altitudes, indicating vertical transport of biomass burning emissions to the upper troposphere.
Edwards, D. P., G. Pétron, P. C. Novelli, L. K. Emmons, J. C. Gille, and J. R. Drummond (2006b), Southern Hemisphere carbon monoxide interannual variability observed by Terra/Measurement of Pollution in the Troposphere (MOPITT), Journal of Geophysical Research: Atmospheres, 111(D16), n/a–n/a, doi:10.1029/2006JD007079.
Biomass burning is an annual occurrence in the tropical Southern Hemisphere (SH) and represents a major source of regional pollution. Vegetation fires emit carbon monoxide (CO), which because of its medium lifetime is an excellent tracer of tropospheric transport. CO is also one of the few tropospheric trace gases currently observed from satellite, and this provides long-term global measurements. In this paper, we use the 5-year CO data record from the Measurement of Pollution in the Troposphere (MOPITT) instrument to examine the interannual variability of the SH CO loading and show how this relates to climate conditions which determine the intensity of fire sources. The MOPITT observations show an annual austral springtime peak in the SH zonal CO loading each year with dry season biomass burning emissions in South America, southern Africa, the maritime continent, and northwestern Australia. Although fires in southern Africa and South America typically produce the greatest amount of CO, the most significant interannual variation is due to varying fire activity and emissions from the maritime continent and northern Australia. We find that this variation in turn correlates well with the El Niño–Southern Oscillation precipitation index. Between 2000 and 2005, emissions were greatest in late 2002, and an inverse modeling of the MOPITT data using the Model of Ozone Research in the Troposphere (MOZART) chemical transport model estimates the Southeast Asia regional fire source for the year August 2002 to September 2003 to be 52 Tg CO. Comparison of the MOPITT retrievals and NOAA surface network measurements indicate that the latter do not fully capture the interannual variability or the seasonal range of the CO zonal average concentration because of biases associated with atmospheric and geographic sampling.
Kar, J., J. R. Drummond, D. B. A. Jones, J. Liu, F. Nichitiu, J. Zou, J. C. Gille, D. P. Edwards, and M. N. Deeter (2006), Carbon monoxide (CO) maximum over the Zagros mountains in the Middle East: Signature of mountain venting?, Geophysical Research Letters, 33(15), n/a–n/a, doi:10.1029/2006GL026231.
We report an intriguing feature observed in daytime measurements of CO over the Middle East, in spring and summer, by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument. Enhanced CO is observed over the Zagros mountains of Iran, following the local topography over this region (25–40N, 40–60E). The MOPITT averaging kernels do not seem to indicate any data artifacts in this area. We argue that this feature likely forms by the process of mountain venting by thermal winds caused by strong daytime differential heating. This is consistent with an analysis of vertical velocity in the NCEP reanalysis data in this region. The phenomenon was observed in all the years of available MOPITT measurements and may have implications for the pollution episodes in the region and the Middle East ozone maximum that has been observed earlier.
Liu, J., J. R. Drummond, D. B. A. Jones, Z. Cao, H. Bremer, J. Kar, J. Zou, F. Nichitiu, and J. C. Gille (2006), Large horizontal gradients in atmospheric CO at the synoptic scale as seen by spaceborne Measurements of Pollution in the Troposphere, Journal of Geophysical Research: Atmospheres, 111(D2), n/a–n/a, doi:10.1029/2005JD006076.
We have examined the influence of synoptic processes on the distribution of atmospheric CO as observed by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument. In the MOPITT data, large horizontal gradients in CO, coherent at the synoptic scale, have been observed. The concentration of CO varies rapidly by as much as 50–100% across distances of ∼100 km, forming distinct boundaries in the CO distribution. These can last one to several days and span horizontal distances of 600–1000 km. On average, such events were observed in the MOPITT CO daily images once every 3–4 days over North America in spring and summer 2000. We focused on three case studies over North America in August 2000 to understand the mechanisms responsible for the large gradients in CO. Through an analysis of meteorological data from the National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis, parcel trajectory modeling, and global three-dimensional chemical transport modeling, we found that the large horizontal gradients typically reflect the differential vertical and horizontal transport of air with different chemical signatures. In the first case, the large gradients in CO over North Dakota resulted from the lifting ahead of a cold front that transported boundary layer air enriched with CO from forest fires in Montana, combined with the descent of clean air from the Canadian Prairies behind the front. In the second case, the large gradients over northeastern Texas were produced by the convective lifting over Arkansas of air with high concentrations of CO from the oxidation of volatile organic compounds and the onshore transport of clean air from the Gulf of Mexico. In the third case, we examined an example of outflow of surface pollution from North America by a cyclone. The largest gradients in this case were observed along the boundary between the boundary layer air transported by the warm conveyor belt ahead of the cold front and the clean air transported from the Atlantic by the semipermanent high-pressure system in the central Atlantic. Our results demonstrate that MOPITT can capture the influence of synoptic processes on the horizontal and vertical distribution of CO. The large gradients in CO observed on synoptic scales represent valuable information that can be exploited to improve our understanding of atmospheric CO. In particular, these results suggest that the MOPITT observations provide a useful data set with which to address a range of issues from air quality on local/regional scales to long-range transport of pollution on continental/global scales.
Massie, S. T., J. C. Gille, D. P. Edwards, and S. Nandi (2006), Satellite observations of aerosol and CO over Mexico City, Atmospheric Environment, 40(31), 6019–6031, doi:10.1016/j.atmosenv.2005.11.065.
The development of remote sensing satellite technology potentially will lead to the technical means to monitor air pollution emitted from large cities on a global basis. This paper presents observations by the moderate resolution imaging spectroradiometer (MODIS) and measurements of pollution in the troposphere (MOPITT) experiments of aerosol optical depths and CO mixing ratios, respectively, in the vicinity of Mexico City to illustrate current satellite capabilities. MOPITT CO mixing ratios over Mexico City, averaged between January–March 2002–2005, are 19% above regional values and the CO plume extends over 10°2 in the free troposphere at 500 hPa. Time series of Red Automatica de Monitoreo Ambiental (RAMA) PM10, and (Aerosol Robotic Network) AERONET and MODIS aerosol optical depths, and RAMA and MOPITT CO time series are inter-compared to illustrate the different perspectives of ground based and satellite instrumentation. Finally, we demonstrate, by examining MODIS and MOPITT data in April 2003, that satellite data can be used to identify episodes in which pollution form fires influences the time series of ground based and satellite observations of urban pollution.
Pradier, S., J.-L. Attie, M. Chong, J. Escobar, V.-H. Peuch, J.-F. Lamarque, B. Khattatov, and D. Edwards (2006), Evaluation of 2001 springtime CO transport over West Africa using MOPITT CO measurements assimilated in a global chemistry transport model, Tellus B, 58(3), 163–176, doi:10.1111/j.1600-0889.2006.00185.x.
The global chemistry and transport model MOCAGE (Modèle de Chimie Atmosphérique à Grande Echelle) is used to investigate the contribution of transport to the carbon monoxide (CO) distribution over West Africa during spring 2001. It is constrained with the CO profiles provided by the Measurements Of Pollution In The Troposphere (MOPITT) instrument through a sequential assimilation technique based on a suboptimal Kalman filter. The improvement of tropospheric CO distribution from MOCAGE is evaluated by comparing the model results (with and without assimilation) with the MOPITT CO concentrations observed during the analysed period (between 2001 March 15 to 2001 April 30), and also with independent in situ CMDL and TRACE-P observations. The initial overestimation in high CO emissions areas (Africa, SE Asia and NW coast of South America) is considerably reduced by using the MOPITT CO assimilation. We analysed the assimilated CO for a period of three successive 15 d periods in terms of average fields over West Africa and contributions to the CO budget of transport and chemical sources. It is found that the horizontal and vertical CO distributions are strongly dependent on the characteristics of the large-scale flows during spring, marked by the onset of the low-level southerly monsoon flow and the gradual increase of the well-known African and tropical easterly jets at middle and upper levels, respectively. Total transport by the mean flow (horizontal plus vertical advection) is important in the CO budget since it mostly compensates the local sink or source generated by chemical reactions and small-scale processes. The major source of CO is concentrated in the lower troposphere (1000-800 hPa) mainly due to convergent low-level flow advecting CO from surrounding regions and surface emissions (biomass burning). Vertical transport removes 70% of this low-level CO and redistributes it in the middle troposphere (800-400 hPa) where chemical reactions and horizontal exports contribute to the loss of CO. A lesser proportion is transported upwards into upper troposphere, and then horizontally, out of the considered domain.
Rinsland, C. P., M. Luo, J. A. Logan, R. Beer, H. Worden, S. S. Kulawik, D. Rider, G. Osterman, M. Gunson, A. Eldering, A. Goldman, M. Shephard, S. A. Clough, C. Rodgers, M. Lampel, and L. Chiou (2006), Nadir measurements of carbon monoxide distributions by the Tropospheric Emission Spectrometer instrument onboard the Aura Spacecraft: Overview of analysis approach and examples of initial results, Geophysical Research Letters, 33(22), n/a–n/a, doi:10.1029/2006GL027000.
We provide an overview of the nadir measurements of carbon monoxide (CO) obtained thus far by the Tropospheric Emission Spectrometer (TES). The instrument is a high resolution array Fourier transform spectrometer designed to measure infrared spectral radiances from low Earth orbit. It is one of four instruments successfully launched onboard the Aura platform into a sun synchronous orbit at an altitude of 705 km on July 15, 2004 from Vandenberg Air Force Base, California. Nadir spectra are recorded at 0.06-cm−1 spectral resolution with a nadir footprint of 5 × 8 km. We describe the TES retrieval approach for the analysis of the nadir measurements, report averaging kernels for typical tropical and polar ocean locations, characterize random and systematic errors for those locations, and describe instrument performance changes in the CO spectral region as a function of time. Sample maps of retrieved CO for the middle and upper troposphere from global surveys during December 2005 and April 2006 highlight the potential of the results for measurement and tracking of global pollution and determining air quality from space.
Shindell, D. T., G. Faluvegi, D. S. Stevenson, M. C. Krol, L. K. Emmons, J.-F. Lamarque, G. Pétron, F. J. Dentener, K. Ellingsen, M. G. Schultz, O. Wild, M. Amann, C. S. Atherton, D. J. Bergmann, I. Bey, T. Butler, J. Cofala, W. J. Collins, R. G. Derwent, R. M. Doherty, J. Drevet, H. J. Eskes, A. M. Fiore, M. Gauss, D. A. Hauglustaine, L. W. Horowitz, I. S. A. Isaksen, M. G. Lawrence, V. Montanaro, J.-F. Müller, G. Pitari, M. J. Prather, J. A. Pyle, S. Rast, J. M. Rodriguez, M. G. Sanderson, N. H. Savage, S. E. Strahan, K. Sudo, S. Szopa, N. Unger, T. P. C. van Noije, and G. Zeng (2006), Multimodel simulations of carbon monoxide: Comparison with observations and projected near-future changes, Journal of Geophysical Research: Atmospheres, 111(D19), n/a–n/a, doi:10.1029/2006JD007100.
We analyze present-day and future carbon monoxide (CO) simulations in 26 state-of-the-art atmospheric chemistry models run to study future air quality and climate change. In comparison with near-global satellite observations from the MOPITT instrument and local surface measurements, the models show large underestimates of Northern Hemisphere (NH) extratropical CO, while typically performing reasonably well elsewhere. The results suggest that year-round emissions, probably from fossil fuel burning in east Asia and seasonal biomass burning emissions in south-central Africa, are greatly underestimated in current inventories such as IIASA and EDGAR3.2. Variability among models is large, likely resulting primarily from intermodel differences in representations and emissions of nonmethane volatile organic compounds (NMVOCs) and in hydrologic cycles, which affect OH and soluble hydrocarbon intermediates. Global mean projections of the 2030 CO response to emissions changes are quite robust. Global mean midtropospheric (500 hPa) CO increases by 12.6 ± 3.5 ppbv (16%) for the high-emissions (A2) scenario, by 1.7 ± 1.8 ppbv (2%) for the midrange (CLE) scenario, and decreases by 8.1 ± 2.3 ppbv (11%) for the low-emissions (MFR) scenario. Projected 2030 climate changes decrease global 500 hPa CO by 1.4 ± 1.4 ppbv. Local changes can be much larger. In response to climate change, substantial effects are seen in the tropics, but intermodel variability is quite large. The regional CO responses to emissions changes are robust across models, however. These range from decreases of 10–20 ppbv over much of the industrialized NH for the CLE scenario to CO increases worldwide and year-round under A2, with the largest changes over central Africa (20–30 ppbv), southern Brazil (20–35 ppbv) and south and east Asia (30–70 ppbv). The trajectory of future emissions thus has the potential to profoundly affect air quality over most of the world’s populated areas.
Tie, X., G. P. Brasseur, C. Zhao, C. Granier, S. Massie, Y. Qin, P. Wang, G. Wang, P. Yang, and A. Richter (2006), Chemical characterization of air pollution in Eastern China and the Eastern United States, Atmospheric Environment, 40(14), 2607–2625, doi:10.1016/j.atmosenv.2005.11.059.
Satellite data (MODIS, GOME, and MOPITT) together with a chemical transport global model of the atmosphere (MOZART-2) are used to characterize air pollution in Eastern China and the Eastern US to assess the differences between the photochemical conditions in these two regions. Observations show that aerosol concentrations (both fine (radius&lt;0.5 μm) and coarse modes (radius&gt;0.5 μm)) are higher in Eastern China than in the Eastern US. The NOx concentrations in both regions are substantially higher than in remote regions such as over the oceans (150 compared to 5 (1014 # cm−2) over the Pacific Ocean). The CO concentrations are high in both urbanized areas (30 compared to 10 (1017 # cm−2) over the Pacific Ocean). However, the concentrations of non-methane hydrocarbons from both anthropogenic and biogenic sources are considerably lower in Eastern China than in the Eastern US. As a result, the rate of photochemical ozone production and ozone concentrations during summer is significantly lower in Eastern China (daily averaged concentrations of 40–50 ppbv in summer) than in the Eastern US (daily averaged values of 60–70 ppbv). The analysis also shows that in Eastern China, the O3 production is mainly due to the oxidation of carbon monoxide (54% of total O3 production), while, in the Eastern US, the O3 production is attributed primarily to the oxidation of reactive hydrocarbons (68% of total O3 production). The results also indicate that biogenic emissions of hydrocarbons contribute substantially to the production of O3 in the Eastern US. The O3 production due to the oxidation of biogenic hydrocarbons represents approximately one third of total O3 photochemical production in this region. Measurements of surface ozone in the Eastern US and Eastern China seem to support that the summer ozone production is lower in Eastern China than in the Eastern US. However, additional surface measurements, especially of reactive hydrocarbons and ozone are needed in Eastern China in order to improve the present analysis and to confirm our current conclusions. A sensitivity study shows that with increase in anthropogenic emissions of HCs, the surface ozone concentrations significantly increase in Eastern China, indicating that the increase in the emissions of HCs plays an important role for the enhancement in surface ozone in this region.
Zhao, C., X. Tie, G. Wang, Y. Qin, and P. Wang (2006), Analysis of Air Quality in Eastern China and its Interaction with Other Regions of the World, J Atmos Chem, 55(3), 189–204, doi:10.1007/s10874-006-9022-1.
In this study, we used satellite data (GOME and MOPITT) together with a global chemical-transport-model of atmosphere (MOZART-2) to characterize the chemical/aerosol composition over eastern China. We then estimated the effects of local emissions in China on the chemical budgets in other regions of the world. Likewise, we also investigated the effects of air pollution from other regions on the chemical budget over eastern China. The study shows that the column CO and NO x concentrations are also high in eastern China. The high CO and NO x concentrations produce modest levels of O3 concentrations during summer (about 40 to 50 ppbv) and very low O3 during winter (about 10 to 20 ppbv) in eastern China. The calculated NO2 column is fairly consistent from the GOME measurement. The calculated CO column is underestimated from the MOPITT measurement. One of the reasons of the underestimation of the predicted CO is due to a fact that the CO emissions were taken without considering the rapid increase of emissions from 1990 to 2000. The calculated surface O3 is consistent with the measured values, with strong seasonal variations. However, the measurement is very limited, and more measurements in eastern China will be needed. The column NO2 has a very strong seasonal variation in eastern China, with the highest concentrations during winter and the lowest concentrations during summer. The cause of this seasonal variability is mainly due to the seasonal changes in the chemical loss of NO x , which is very high in summer and very low during winter. The effects of the local emissions in China and long-range transport from other regions on the chemical distributions in eastern China are studied. The results show that NO x concentrations in eastern China are mostly caused by the local emissions in China, especially during the winter. The CO concentration over eastern China is from both the local emissions (30% to 40%) and the transport from other regions. Likewise, the CO emissions in China have an important effect on the other regions of the world, but the effect is limited in the northern hemisphere. The local emissions in China also have an important effect on surface O3 concentrations. During winter, the local emissions reduce the surface O3 concentrations by 30 to 50%. During summer, the local emissions produce about 50 to 70% of the O3 concentration in eastern China.


Ho, S.-P., D. P. Edwards, J. C. Gille, J. Chen, D. Ziskin, G. L. Francis, M. N. Deeter, and J. R. Drummond (2005), Estimates of 4.7 μm surface emissivity and their impact on the retrieval of tropospheric carbon monoxide by Measurements of Pollution in the Troposphere (MOPITT), Journal of Geophysical Research (Atmospheres), 110(d9), 21308, doi:10.1029/2005JD005946.
Carbon monoxide (CO) is an important tropospheric trace species. The Measurements of Pollution in the Troposphere (MOPITT) instrument uses the 4.7 μm CO band to measure the global CO profile and total column amount in the troposphere from space. In the operational MOPITT CO retrieval algorithm, surface skin temperature (Ts) and emissivity (E) are retrieved simultaneously with the CO profile. However, because both Ts and E are retrieved from the same piece of information from the MOPITT measurements, the accuracy of both variables may be limited, which leads to an increase of uncertainty in the CO retrievals. An accurate specification of the surface skin temperature is required to determine surface emissivity and vice versa. In this study, a method is developed which uses Ts from the Moderate Resolution Imaging Spectroradiometer (MODIS) and MOPITT radiances to derive an improved 4.7 μm surface emissivity estimate (E) for use in retrievals by the MOPITT instrument. Monthly mean 4.7 μm surface emissivity maps for 1 year are generated and used as the a priori E in the MOPITT Ts and CO retrieval algorithm. We show that the geographical distribution of the 4.7 μm emissivity is very consistent with MODIS normalized difference vegetation index distribution, which is strongly tied to the surface emissivity. This a priori E has a much smaller standard deviation than values currently used in the MOPITT retrieval. As a result, more radiance information tends to be used in the MOPITT Ts and CO retrievals. By using the improved a priori E over the land, the information content of MOPITT radiances increases 15% at night and 5% during the day relative to the current version MOPITT data products. The difference between day and night information content (or diurnal difference) decreases from 0.3 (current version) to 0.21, showing that nighttime retrievals are improved. Over the global ocean the diurnal difference of the MOPITT information content decreases from 0.15 (current version) to 0.06. The differences between the new profile retrievals and those of current profile retrievals are very consistent with their corresponding diurnal and geographical information content distributions. Over the global ocean the new MOPITT CO profile is lower by 3-11% during the night in the lower troposphere. Over the global land the new CO profile is higher by 3.2% in the lower troposphere during the night. The differences between the new profile retrieval and those of current retrieval are small during the day.
Liu, J., J. R. Drummond, Q. Li, J. C. Gille, and D. C. Ziskin (2005), Satellite mapping of CO emission from forest fires in Northwest America using MOPITT measurements, Remote Sensing of Environment, 95(4), 502–516, doi:10.1016/j.rse.2005.01.009.
We present a study on MOPITT (Measurements Of Pollution In The Troposphere) detection of CO emission from large forest fires in the year 2000 in the northwest United States. Fire data used are from the space-borne Advanced Very High Resolution Radiometer (AVHRR) at 1-km resolution. The study shows that MOPITT can reliably detect CO plumes from forest fires whenever there are &gt;30 AVHRR hotspots in a 0.25° × 0.25° grid, which is comparable to the pixel area of MOPITT in the region. The spatial CO pattern during the fire events is found to be consistent with the location and density of AVHRR hotspots and wind direction. While the increase of CO abundance inside the study area is closely correlated to the AVHRR-derived hotspot number in general (R &gt; 0.75), the non-linearity of fire emission with fuel consumption is also observed. MOPITT can also capture the temporal variation in CO emission from forest fires through 3-day composites so it may offer an opportunity to enhance our knowledge of temporal fire emission over large areas. The CO emission is quantitatively estimated with a one-box model. The result is compared with a bottom-up approach using surface data including burnt area, biomass density, and fire emission factors. If mean emission factors for the region are used, the bottom-up approach results in total emission estimates which are 10%–50% lower than the MOPITT-based estimate. In spite of the limitations and uncertainties addressed in this study, MOPITT data may provide a useful constraint on uncertain ground-based fire emission estimates.
Pfister, G., J. C. Gille, D. Ziskin, G. Francis, D. P. Edwards, M. N. Deeter, and E. Abbott (2005a), Effects of a Spectral Surface Reflectance on Measurements of Backscattered Solar Radiation: Application to the MOPITT Methane Retrieval, Journal of Atmospheric and Oceanic Technology, 22(5), 566–574, doi:10.1175/JTECH1721.1.
The amount of solar radiation emerging from the top of the atmosphere is strongly influenced by the reflectance of the underlying surface. For this reason, some information about the magnitude and the spectral variability of the surface reflectance typically has to be included in the retrieval of atmospheric parameters from reflected solar radiation measurements. Sufficient information about the surface reflectance properties is rarely available, and the integration of this effect in the retrieval might turn out to be a challenge, especially for broadband instruments. In this paper the focus is on the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument. Theoretical studies are performed to investigate how a spectrally varying surface reflectance might impact the retrieval of the total column amount of methane from MOPITT radiance measurements, and the current findings are compared to observed biases. However, the findings present herein might be valuable and applicable for other remote sensing instruments that are sensitive to the amount of solar radiation reflected from the earth’s surface.
Pfister, G., P. G. Hess, L. K. Emmons, J.-F. Lamarque, C. Wiedinmyer, D. P. Edwards, G. Pétron, J. C. Gille, and G. W. Sachse (2005b), Quantifying CO emissions from the 2004 Alaskan wildfires using MOPITT CO data, Geophysical Research Letters, 32, 11809, doi:10.1029/2005GL022995.
We present an inverse model analysis to quantify the emissions of wildfires in Alaska and Canada in the summer of 2004 using carbon monoxide (CO) data from the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument together with the chemistry transport model MOZART (Model for Ozone and Related Chemical Tracers). We use data assimilation outside the region of the fires to optimally constrain the CO background level and the transport into that region. Inverse modeling is applied locally to quantify the fire emissions. Our a posteriori estimate of the wildfire emissions gives a total of 30 +/- 5 Tg CO emitted during June-August 2004 which is of comparable order to the anthropogenic emissions for the continental US. The simulated CO fields have been evaluated by comparison with MOPITT and independent aircraft data.
Shindell, D. T., G. Faluvegi, and L. K. Emmons (2005), Inferring carbon monoxide pollution changes from space-based observations, Journal of Geophysical Research: Atmospheres, 110(D23), n/a–n/a, doi:10.1029/2005JD006132.
We compare space-based measurements of carbon monoxide (CO) during April 1994 and October 1984 and 1994 from the early MAPS instrument with those during 2000–2004 from the MOPITT instrument. We show that a three-dimensional global composition model can be used to account for differences in retrieval sensitivity between the two instruments and between the different years of MOPITT data. This allows direct comparison of CO amounts over most of the globe at different times. These types of changes in short-lived constituents cannot be assessed with local measurements. Though the existing space-based data are too sparse both temporally and geographically to allow trend estimates, we find substantial variations in midtropospheric CO between the different years in many continental-scale regions. During April, average CO is ∼12–18 ppbv (∼10–20%) greater during 2000–2004 than during 1994 over North America, southeast Asia and North Africa though the global mean value is nearly the same. During October 1994, observations show CO enhancements of 15–20 ppbv relative to 1984 or 2000–2004 over South America and a similar, though slightly smaller (9–19 ppbv), enhancement globally. Southeast Asia, Europe and North America all show similar October CO levels in 1994 and 2000–2004, with both times showing substantially more pollution (13–29 ppbv) than 1984. Variations over Europe and Africa are consistent in both seasons, while changes elsewhere are not. Changes over southeast Asia and North Africa are substantially in excess of interannual variability, while those over North and South America and southern Africa are only marginally so. Model sensitivity studies examining the response to changes in emissions indicate probable causes of the CO changes over different regions. Over southeast Asia and North America, CO is most sensitive to industrial and biomass burning emissions, implying that changes in these sources likely account for the 13–29 ppbv increases seen there between 2000–2004 and earlier years. Over North Africa, CO is strongly influenced by numerous sources as well as meteorology, precluding attribution of increases to particular factors. Over South America and southern Africa, variations in both biomass burning and isoprene emissions likely contributed to the ∼10–20 ppbv changes.
Yurganov, L. N., P. Duchatelet, A. V. Dzhola, D. P. Edwards, F. Hase, I. Kramer, E. Mahieu, J. Mellqvist, J. Notholt, P. C. Novelli, A. Rockmann, H. E. Scheel, M. Schneider, A. Schulz, A. Strandberg, R. Sussmann, H. Tanimoto, V. Velazco, J. R. Drummond, and J. C. Gille (2005), Increased Northern Hemispheric carbon monoxide burden in the troposphere in 2002 and 2003 detected from the ground and from space, Atmos. Chem. Phys., 5(2), 563–573, doi:10.5194/acp-5-563-2005.
Carbon monoxide total column amounts in the atmosphere have been measured in the High Northern Hemisphere (30°-90° N, HNH) between January 2002 and December 2003 using infrared spectrometers of high and moderate resolution and the Sun as a light source. They were compared to ground-level CO mixing ratios and to total column amounts measured from space by the Terra/MOPITT instrument. All these data reveal increased CO abundances in 2002-2003 in comparison to the unperturbed 2000-2001 period. Maximum anomalies were observed in September 2002 and August 2003. Using a simple two-box model, the corresponding annual CO emission anomalies (referenced to 2000-2001 period) have been found equal to 95Tg in 2002 and 130Tg in 2003, thus close to those for 1996 and 1998. A good correlation with hot spots detected by a satellite radiometer allows one to assume strong boreal forest fires, occurred mainly in Russia, as a source of the increased CO burdens.


Bremer, H., J. Kar, J. R. Drummond, F. Nichitu, J. Zou, J. Liu, J. C. Gille, M. N. Deeter, G. Francis, D. Ziskin, and J. Warner (2004), Spatial and temporal variation of MOPITT CO in Africa and South America: A comparison with SHADOZ ozone and MODIS aerosol, Journal of Geophysical Research: Atmospheres, 109(D12), n/a–n/a, doi:10.1029/2003JD004234.
Carbon monoxide (CO) measurements from the Measurements of Pollution in the Troposphere (MOPITT) experiment are used to explore the correlation between biomass burning and ozone profiles at six tropical stations namely Reunion, Irene, Natal, Ascension, San Cristobal, and Paramaribo. Distinct seasonal patterns of CO at each station indicate the strong influence of African and South American biomass burning. All stations show enhanced CO columns during September–November (SON) corresponding to austral burning. Furthermore, the effects of Sahelian burning can be seen at Natal and Ascension. Similarly, the signature of northern Amazonian fires can be observed at San Cristobal. The CO variations are generally similar to the variations of aerosol optical depth (AOD) retrieved contemporaneously from Moderate Resolution Imaging Spectroradiometer (MODIS) at most stations, with notable differences at Irene, San Cristobal, and Paramaribo. Tropospheric ozone from Southern Hemisphere Additional Ozonesonde (SHADOZ) ozonesonde measurements at all stations show elevated levels, corresponding to the CO enhancements in SON months. However, there are several instances of ozone enhancements unaccompanied by any CO increase. This might indicate that sources other than biomass burning such as stratospheric tropospheric exchange (STE) or lightning related NOx may be operative. At San Cristobal, strong CO enhancements during March–April are not accompanied by any significant change in ozone.
Crawford, J. H., C. L. Heald, H. E. Fuelberg, D. M. Morse, G. W. Sachse, L. K. Emmons, J. C. Gille, D. P. Edward, M. N. Deeter, G. Chen, J. R. Olson, V. S. Connors, C. Kittaka, and A. J. Hamlin (2004), Relationship between Measurements of Pollution in the Troposphere (MOPITT) and in situ observations of CO based on a large-scale feature sampled during TRACE-P, Journal of Geophysical Research (Atmospheres), 109(d18), 15, doi:10.1029/2003JD004308.
During Transport and Chemical Evolution over the Pacific (TRACE-P), there were several opportunities to perform in situ sampling coincident with overpasses of the Measurements of Pollution in the Troposphere (MOPITT) instrument on board the EOS Terra satellite. This sampling consisted of in situ vertical profiles of CO by NASA’s DC-8 aircraft intended to provide data useful for validating MOPITT observations of CO column. One particular profile conducted over the central North Pacific revealed a layer of pollution characterized by CO mixing ratios more than double background values. Sampling of the surrounding region by both the NASA DC-8 and P-3B aircraft showed this layer to have a considerable geographic extent, at least 25° longitude (∼2500 km) and 4° latitude (∼400 km). Using back trajectory analysis, this polluted layer is followed back in time and compared with four consecutive MOPITT overpasses. MOPITT observations during these four overpasses agree well with the location of the layer as inferred by the trajectories; however, the detected CO column amount increases backward in time by just over 20%. Further analysis shows that the majority of this change in detected column abundance is consistent with two factors: (1) changes in the thickness of the polluted layer over time (9 +/- 3%) and (2) changes in retrieved column abundance due to the altitude of the layer (7 +/- 3%). This demonstrates that there are both real and artificial sources of variability that must be understood before MOPITT observations can be quantitatively useful. An unexpected finding was the difference in the variance of MOPITT observations depending on whether observations were taken under daylight or nighttime conditions. The variance in daytime observations of the polluted layer was approximately double that for nighttime data. The results of this analysis indicate that targeted in situ sampling of large-scale pollution events can provide insight leading to more realistic interpretation of MOPITT observations. Strategies for sampling such events repeatedly during their evolution could also provide more interesting opportunities for validation.
Deeter, M. N., L. K. Emmons, G. L. Francis, D. P. Edwards, J. C. Gille, J. X. Warner, B. Khattatov, D. Ziskin, J.-F. Lamarque, S.-P. Ho, V. Yudin, J.-L. Attie, D. Packman, J. Chen, D. Mao, J. R. Drummond, P. Novelli, and G. Sachse (2004a), Evaluation of operational radiances for the Measurements of Pollution in the Troposphere (MOPITT) instrument CO thermal band channels, Journal of Geophysical Research: Atmospheres, 109(D3), n/a–n/a, doi:10.1029/2003JD003970.
The ability of operational radiative transfer models to accurately predict remote sensing instrument observations (e.g., calibrated radiances) over a wide variety of geophysical situations is critical to the performance of trace gas retrieval algorithms. As part of the validation of the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument, we present a technique for comparing operational calibrated thermal band (4.7 μm) Earth-view MOPITT radiances with corresponding values calculated using the MOPITT operational radiative transfer model. In situ carbon monoxide (CO) profiles sampled from aircraft in coordination with MOPITT overpasses serve as the foundation for MOPITT validation. Characteristics of radiance errors due to in situ sampling characteristics, CO temporal and spatial variability, and surface emissivity are discussed. Results indicate that radiance biases for most of the MOPITT thermal channel radiances are typically on the order of 1%. Observed radiance biases are largest and most variable for the pressure modulation cell difference-signal radiances, probably because of the lack of in situ data in the upper troposphere and lower stratosphere.
Deeter, M. N., L. K. Emmons, D. P. Edwards, J. C. Gille, and J. R. Drummond (2004b), Vertical resolution and information content of CO profiles retrieved by MOPITT, Geophysical Research Letters, 31, 15112, doi:10.1029/2004GL020235.
The MOPITT (Measurements of Pollution in the Troposphere) remote sensing instrument monitors the global distribution of carbon monoxide from a polar-orbiting platform. Calculated averaging kernels for operational MOPITT CO profiles indicate the capability of independently retrieving mid- and upper-tropospheric CO. The information content in MOPITT retrievals is objectively quantified through calculation of the Degrees of Freedom for Signal (DFS), which indicates the number of independent pieces of information in the retrieved profile. DFS values larger than 1 (indicating some amount of profile shape information) are common in tropical and midlatitude scenes. The existence of shape information in actual MOPITT retrieved profiles is also verified through (1) a quantitative comparison with in-situ data acquired as part of MOPITT validation and (2) a qualitative comparison with monthly mean rain rate (as an index for convection) in the Tropical Eastern Pacific Ocean.
Edwards, D. P., L. K. Emmons, D. A. Hauglustaine, D. A. Chu, J. C. Gille, Y. J. Kaufman, G. Pétron, L. N. Yurganov, L. Giglio, M. N. Deeter, V. Yudin, D. C. Ziskin, J. Warner, J.-F. Lamarque, G. L. Francis, S. P. Ho, D. Mao, J. Chen, E. I. Grechko, and J. R. Drummond (2004), Observations of carbon monoxide and aerosols from the Terra satellite: Northern Hemisphere variability, Journal of Geophysical Research (Atmospheres), 109(d18), 24202, doi:10.1029/2004JD004727.
Measurements from the Terra satellite launched in December of 1999 provide a global record of the recent interannual variability of tropospheric air quality: carbon monoxide (CO) from the Measurement of Pollution in the Troposphere (MOPITT) instrument and aerosol optical depth (AOD) from the Moderate-Resolution Imaging Spectroradiometer (MODIS). This paper compares and contrasts these data sets with a view to understanding the general features of the overall pollutant loading of the Northern Hemisphere (NH). We present a detailed examination of the seasonal and recent interannual variability of the fine mode AOD and CO column, first considering the variation of the global zonal average for both quantities, and then concentrating on several geographical regions with the aim of isolating different emissions. In a zonal sense, the principal NH sources are related to anthropogenic urban and industrial activity. We show that both the CO and the AOD zonal seasonal variations reflect the atmospheric oxidant concentration, which determines the primary sink of CO and the production of sulfate aerosol. As a consequence, the seasonal cycles are several months out of phase, with perturbations resulting from sporadic wildfire or biomass-burning emissions. In these cases, carbonaceous particles dominate the AOD, and this results in the best correlation with the CO column. Of the 4 years of data available from the Terra satellite, the winter and spring of 2002-2003 showed anomalously high NH pollution compared to the previous years. This was a result of fires in western Russia in the late summer and fall of 2002 and intense fires in the southeast of Russia in the spring and summer of 2003. We examine these events using fire counts from MODIS to indicate the burning regions and investigate how the timing of the fires in relation to atmospheric oxidant concentrations affects the resultant seasonal pollutant loadings. Finally, we trace the emissions from these fires to indicate how intense local pollution sources can impact continental- and global-scale air quality.
Emmons, L. K., M. N. Deeter, J. C. Gille, D. P. Edwards, J.-L. Attié, J. Warner, D. Ziskin, G. Francis, B. Khattatov, V. Yudin, J.-F. Lamarque, S.-P. Ho, D. Mao, J. S. Chen, J. Drummond, P. Novelli, G. Sachse, M. T. Coffey, J. W. Hannigan, C. Gerbig, S. Kawakami, Y. Kondo, N. Takegawa, H. Schlager, J. Baehr, and H. Ziereis (2004), Validation of Measurements of Pollution in the Troposphere (MOPITT) CO retrievals with aircraft in situ profiles, Journal of Geophysical Research: Atmospheres, 109(D3), n/a–n/a, doi:10.1029/2003JD004101.
Validation of the Measurements of Pollution in the Troposphere (MOPITT) retrievals of carbon monoxide (CO) has been performed with a varied set of correlative data. These include in situ observations from a regular program of aircraft observations at five sites ranging from the Arctic to the tropical South Pacific Ocean. Additional in situ profiles are available from several short-term research campaigns situated over North and South America, Africa, and the North and South Pacific Oceans. These correlative measurements are a crucial component of the validation of the retrieved CO profiles and columns from MOPITT. The current validation results indicate good quantitative agreement between MOPITT and in situ profiles, with an average bias less than 20 ppbv at all levels. Comparisons with measurements that were timed to sample profiles coincident with MOPITT overpasses show much less variability in the biases than those made by various groups as part of research field experiments. The validation results vary somewhat with location, as well as a change in the bias between the Phase 1 and Phase 2 retrievals (before and after a change in the instrument configuration due to a cooler failure). During Phase 1, a positive bias is found in the lower troposphere at cleaner locations, such as over the Pacific Ocean, with smaller biases at continental sites. However, the Phase 2 CO retrievals show a negative bias at the Pacific Ocean sites. These validation comparisons provide critical assessments of the retrievals and will be used, in conjunction with ongoing improvements to the retrieval algorithms, to further reduce the retrieval biases in future data versions.
Gros, V., J. Williams, M. G. Lawrence, R. von Kuhlmann, J. van Aardenne, E. Atlas, A. Chuck, D. P. Edwards, V. Stroud, and M. Krol (2004), Tracing the origin and ages of interlaced atmospheric pollution events over the tropical Atlantic Ocean with in situ measurements, satellites, trajectories, emission inventories, and global models, Journal of Geophysical Research: Atmospheres, 109(D22), n/a–n/a, doi:10.1029/2004JD004846.
During a west to east crossing of the tropical Atlantic Ocean in October–November 2002 on R/V Meteor (M55), carbon monoxide (CO) and ozone were continuously monitored, and pressurized air samples were collected and later analyzed in the laboratory for various volatile organic compounds. A sequence of alternating CO and propane rich events were observed over the east Atlantic, the events of enhanced carbon monoxide being out of phase with those observed for propane. A combined study of air mass origin (back trajectories and backward emission sensitivity calculations) and source region distribution comparison (CO satellite data from MOPITT and propane emission data from the EDGAR database) showed that the CO events were due to African biomass burning emissions, whereas the propane events were due to industrial emissions from areas of northern Africa. Both events were associated with elevated ozone. A comparison of the measured concentrations of CO and propane with those simulated by the global Model of Atmospheric Transport and Chemistry-Max Planck Institute for Chemistry (MATCH-MPIC) shows that the model reproduces the general longitudinal gradient observed for both compounds and simulates elevated CO concentrations during the pollution events. However, it systematically overestimates the CO mixing ratios. It is suggested that the northern African biomass burning emissions used in the model are not distributed correctly (incorrect timing) and, in particular, that too high emissions from the region “northern Sudan-Sahel” are used for this period. The model does not capture the influence from industrial emissions from northern Africa, which may be caused by too strong diffusion of the plume.
Heald, C. L., D. J. Jacob, D. B. A. Jones, P. I. Palmer, J. A. Logan, D. G. Streets, G. W. Sachse, J. C. Gille, R. N. Hoffman, and T. Nehrkorn (2004), Comparative inverse analysis of satellite (MOPITT) and aircraft (TRACE-P) observations to estimate Asian sources of carbon monoxide, Journal of Geophysical Research: Atmospheres, 109(D23), n/a–n/a, doi:10.1029/2004JD005185.
We use an inverse model analysis to compare the top-down constraints on Asian sources of carbon monoxide (CO) in spring 2001 from (1) daily MOPITT satellite observations of CO columns over Asia and the neighboring oceans and (2) aircraft observations of CO concentrations in Asian outflow from the TRACE-P aircraft mission over the northwest Pacific. The inversion uses the maximum a posteriori method (MAP) and the GEOS-CHEM chemical transport model (CTM) as the forward model. Detailed error characterization is presented, including spatial correlation of the model transport error. Nighttime MOPITT observations appear to be biased and are excluded from the inverse analysis. We find that MOPITT and TRACE-P observations are independently consistent in the constraints that they provide on Asian CO sources, with the exception of southeast Asia for which the MOPITT observations support a more modest decrease in emissions than suggested by the aircraft observations. Our analysis indicates that the observations do not allow us to differentiate source types (i.e., anthropogenic versus biomass burning) within a region. MOPITT provides ten pieces of information to constrain the geographical distribution of CO sources, while TRACE-P provides only four. The greater information from MOPITT reflects its ability to observe all outflow and source regions. We conducted a number of sensitivity studies for the inverse model analysis using the MOPITT data. Temporal averaging of the MOPITT data (weekly and beyond) degrades the ability to constrain regional sources. Merging source regions beyond what is appropriate after careful selection of the state vector leads to significant aggregation errors. Calculations for an ensemble of realistic assumptions lead to a range of inverse model solutions that has greater uncertainty than the a posteriori errors for the MAP solution. Our best estimate of total Asian CO sources is 361 Tg yr−1, over half of which is attributed to east Asia.
Kar, J., H. Bremer, J. R. Drummond, Y. J. Rochon, D. B. A. Jones, F. Nichitiu, J. Zou, J. Liu, J. C. Gille, D. P. Edwards, M. N. Deeter, G. Francis, D. Ziskin, and J. Warner (2004), Evidence of vertical transport of carbon monoxide from Measurements of Pollution in the Troposphere (MOPITT), Geophysical Research Letters, 31, 23105, doi:10.1029/2004GL021128.
Vertical profiles of carbon monoxide (CO) mixing ratio retrieved from MOPITT measurements have been analyzed. We find that variations in the vertical structure of CO can be detected in the MOPITT data. The Asian summer monsoon plume in CO is observed for the first time as a strong enhancement of CO in the upper troposphere (UT) over India and southern China indicating the effect of deep convective transport. Similarly, zonal mean height latitude cross-sections for the months of September-December, 2002 indicate deep convective transport of CO from biomass burning in the southern tropics. These findings show that MOPITT CO can provide valuable information on vertical transport phenomena in the troposphere.
Lamarque, J.-F., B. Khattatov, V. Yudin, D. P. Edwards, J. C. Gille, L. K. Emmons, M. N. Deeter, J. Warner, D. C. Ziskin, G. L. Francis, S. Ho, D. Mao, J. Chen, and J. R. Drummond (2004), Application of a bias estimator for the improved assimilation of Measurements of Pollution in the Troposphere (MOPITT) carbon monoxide retrievals, Journal of Geophysical Research: Atmospheres, 109(D16), n/a–n/a, doi:10.1029/2003JD004466.
This study discusses an improved technique for the assimilation of carbon monoxide retrievals from the Measurements of Pollution in the Troposphere (MOPITT) instrument in a chemistry-transport model using a suboptimal Kalman filter. An online bias estimator algorithm is employed to identify systematic biases in the model and account for them during the assimilation. Results suggest a large decline (both locally and globally) in the observation minus forecast diagnostics and provide insights about possible model deficiencies by enabling explicit examination of model biases.
Niu, J., M. N. Deeter, J. C. Gille, D. P. Edwards, D. C. Ziskin, G. L. Francis, A. J. Hills, and M. W. Smith (2004), Carbon Monoxide Total Column Retrievals by Use of the Measurements of Pollution in the Troposphere Airborne Test Radiometer, Appl. Opt., 43(24), 4685–4696, doi:10.1364/AO.43.004685.
The Measurements of Pollution in the Troposphere (MOPITT) Airborne Test Radiometer (MATR) uses gas correlation filter radiometry from high-altitude aircraft to measure tropospheric carbon monoxide. This radiometer is used in support of the ongoing validation campaign for the MOPITT instrument aboard the Earth Observation System Terra satellite. A recent study of MATR CO retrievals that used data from the autumn of 2001 in the western United States is presented. Retrievals of the CO total column were performed and compared to in situ sampling with less than 10% retrieval error. Effects that influence retrieval, such as instrument sensitivity, retrieval sensitivity, and the bias between observations and the radiative transfer model, are discussed. Comparisons of MATR and MOPITT retrievals show promising consistency. A preliminary interpretation of MATR results is also presented.
Pétron, G., C. Granier, B. Khattatov, V. Yudin, J.-F. Lamarque, L. Emmons, J. Gille, and D. P. Edwards (2004), Monthly CO surface sources inventory based on the 2000–2001 MOPITT satellite data, Geophysical Research Letters, 31(21), n/a–n/a, doi:10.1029/2004GL020560.
This paper presents results of the inverse modeling of carbon monoxide surface sources on a monthly and regional basis using the MOPITT (Measurement Of the Pollution In The Troposphere) CO retrievals. The targeted time period is from April 2000 to March 2001. A sequential and time-dependent inversion scheme is implemented to correct an a priori set of monthly mean CO sources. The a posteriori estimates for the total anthropogenic (fossil fuel + biofuel + biomass burning) surface sources of CO in TgCO/yr are 509 in Asia, 267 in Africa, 140 in North America, 90 in Europe and 84 in Central and South America. Inverting on a monthly scale allows one to assess a corrected seasonality specific to each source type and each region. Forward CTM simulations with the a posteriori emissions show a substantial improvement of the agreement between modeled CO and independent in situ observations.
Pfister, G., G. Pétron, L. K. Emmons, J. C. Gille, D. P. Edwards, J.-F. Lamarque, J.-L. Attie, C. Granier, and P. C. Novelli (2004), Evaluation of CO simulations and the analysis of the CO budget for Europe, Journal of Geophysical Research: Atmospheres, 109(D19), n/a–n/a, doi:10.1029/2004JD004691.
CO is a well-suited indicator for the transport of pollutants in the troposphere on a regional and global scale. For the study presented here, simulations of CO concentrations from a global chemistry transport model (MOZART-2), with the CO being tagged according to the emission type and the source region, have been used to diagnose the contributions of different processes and regions to the CO burden over Europe. Model simulations have been performed with both a priori emissions and an optimized set of CO surface emissions derived from the inversion of CO retrievals of the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument. The annual mean difference between the modeled and the observed CO at 850 hPa over Europe is −38 ± 13 ppb with the a priori set of emissions and −7 ± 7 ppb when the optimized emissions are employed in the model. The general difficulties arising from an intercomparison of remote sensing data with model simulations are discussed. Besides data from MOPITT, ground-based CO measurements have been employed in the evaluation of the model and its emissions. The comparisons show that the model represents the background conditions as well as large-scale transport relatively well. The budget analysis reveals the predominant impact of the European emissions on CO concentrations near the surface, and a strong impact of sources from Asia and North America on the CO burden in the free troposphere over Europe. On average, the largest contribution (67%) to the anthropogenic (fossil and biofuel sources, biomass burning) CO at the surface originates from regional anthropogenic sources, but further significant impact is evident from North America (14%) and Asia (15%). With increasing altitude, anthropogenic CO from Asia and North America gains in importance, reaching maximum contributions of 32% for North American CO at 500 hPa and 50% for Asian CO at 200 hPa. The impact of European emissions weakens with increasing altitude (8% at 500 hPa).
Yudin, V. A., G. Pétron, J.-F. Lamarque, B. V. Khattatov, P. G. Hess, L. V. Lyjak, J. C. Gille, D. P. Edwards, M. N. Deeter, and L. K. Emmons (2004), Assimilation of the 2000–2001 CO MOPITT retrievals with optimized surface emissions, Geophysical Research Letters, 31(20), n/a–n/a, doi:10.1029/2004GL021037.
The multi-year retrievals of carbon monoxide (CO) by the MOPITT (Measurements Of Pollution In The Troposphere) instrument onboard the NASA Terra satellite provide an opportunity for the first time to study quantitatively the transport and sources of pollution in the mid-troposphere. This paper presents the assimilation of the Phase I (March 3, 2000–May 6, 2001) MOPITT retrievals with optimized CO emissions constrained by monthly MOPITT CO data. The observed-minus-forecast (OmF) CO distributions illustrate improvement of this data analysis compared with the assimilation that employs climatological surface fluxes.


Deeter, M. N., L. K. Emmons, G. L. Francis, D. P. Edwards, J. C. Gille, J. X. Warner, B. Khattatov, D. Ziskin, J.-F. Lamarque, S.-P. Ho, V. Yudin, J.-L. Attié, D. Packman, J. Chen, D. Mao, and J. R. Drummond (2003), Operational carbon monoxide retrieval algorithm and selected results for the MOPITT instrument, Journal of Geophysical Research: Atmospheres, 108(D14), n/a–n/a, doi:10.1029/2002JD003186.
Measurements of Pollution in the Troposphere (MOPITT) is a new remote sensing instrument aboard the Earth Observing System (EOS) “Terra” satellite which exploits gas correlation radiometry principles to quantify tropospheric concentrations of carbon monoxide (CO) and methane (CH4). The MOPITT CO retrieval algorithm employs a nonlinear optimal estimation method to iteratively solve for the CO profile which is statistically most consistent with both the satellite-measured radiances and a priori information. The algorithm’s theoretical basis is described in terms of the observed radiances and their weighting functions, the a priori information, and the retrieval averaging kernels. Examples of actual CO retrievals over scenes with contrasting pollution conditions are demonstrated, and interpreted in the context of the retrieval averaging kernels and a priori.
Edwards, D. P., J.-F. Lamarque, J.-L. Attié, L. K. Emmons, A. Richter, J.-P. Cammas, J. C. Gille, G. L. Francis, M. N. Deeter, J. Warner, D. C. Ziskin, L. V. Lyjak, J. R. Drummond, and J. P. Burrows (2003), Tropospheric ozone over the tropical Atlantic: A satellite perspective, Journal of Geophysical Research: Atmospheres, 108(D8), n/a–n/a, doi:10.1029/2002JD002927.
We use satellite sensor measurements to obtain a broad picture of the processes affecting tropical tropospheric O3 production over Africa and the Atlantic in the early part of the year. Terra/MOPITT CO retrievals correlate well with biomass burning fire counts observed by the TRMM/VIRS instrument in Northern Hemisphere savanna regions and allow investigation of the subsequent convection of the biomass burning plume at the intertropical convergence zone and interhemispheric transport. Measurements of NO2 from the ERS-2/GOME instrument enable identification of two important tropical sources of this O3 precursor, biomass burning and lightning. Good correlation is seen between NO2 retrievals and TRMM/LIS lightning flash observations in southern African regions free of biomass burning, thus indicating a probable lightning source of NOx. The combination of MOPITT CO, GOME NO2, and TRMM fire and lightning flash counts provides a powerful tool for investigating the tropospheric production of O3 precursors. These data are used in conjunction with the MOZART-2 chemical transport model to investigate the early year tropical Atlantic tropospheric O3 distribution using January 2001 as a case study. Inconsistencies between the various tropical tropospheric O3 column products obtained from EP/TOMS data, and between these products, in situ measurements, and modeling, have led to questions about how the Northern Hemisphere biomass burning is connected to the TOMS derived O3 maximum in the tropical southern Atlantic. We show that the early year tropical O3 distribution is actually characterized by two maxima. The first arises due to biomass burning emissions, is located near the Northern Hemisphere fires, and is most evident in the lower troposphere. The second is located in the southern tropical Atlantic midtroposphere, and results from NOx produced by lightning over southern Africa and South America.
Heald, C. L., D. J. Jacob, A. M. Fiore, L. K. Emmons, J. C. Gille, M. N. Deeter, J. Warner, D. P. Edwards, J. H. Crawford, A. J. Hamlin, G. W. Sachse, E. V. Browell, M. A. Avery, S. A. Vay, D. J. Westberg, D. R. Blake, H. B. Singh, S. T. Sandholm, R. W. Talbot, and H. E. Fuelberg (2003), Asian outflow and trans-Pacific transport of carbon monoxide and ozone pollution: An integrated satellite, aircraft, and model perspective, Journal of Geophysical Research: Atmospheres, 108(D24), n/a–n/a, doi:10.1029/2003JD003507.
Satellite observations of carbon monoxide (CO) from the Measurements of Pollution in the Troposphere (MOPITT) instrument are combined with measurements from the Transport and Chemical Evolution Over the Pacific (TRACE-P) aircraft mission over the northwest Pacific and with a global three-dimensional chemical transport model (GEOS-CHEM) to quantify Asian pollution outflow and its trans-Pacific transport during spring 2001. Global CO column distributions in MOPITT and GEOS-CHEM are highly correlated (R2 = 0.87), with no significant model bias. The largest regional bias is over Southeast Asia, where the model is 18% too high. A 60% decrease of regional biomass burning emissions in the model (to 39 Tg yr−1) would correct the discrepancy; this result is consistent with TRACE-P observations. MOPITT and TRACE-P also give consistent constraints on the Chinese source of CO from fuel combustion (181 Tg CO yr−1). Four major events of trans-Pacific transport of Asian pollution in spring 2001 were seen by MOPITT, in situ platforms, and GEOS-CHEM. One of them was sampled by TRACE-P (26–27 February) as a succession of pollution layers over the northeast Pacific. These layers all originated from one single event of Asian outflow that split into northern and southern plumes over the central Pacific. The northern plume (sampled at 6–8 km off California) had no ozone enhancement. The southern subsiding plume (sampled at 2–4 km west of Hawaii) contained a 8–17 ppbv ozone enhancement, driven by decomposition of peroxyacetylnitrate (PAN) to nitrogen oxides (NOx). This result suggests that PAN decomposition in trans-Pacific pollution plumes subsiding over the United States could lead to significant enhancements of surface ozone.
Jacob, D. J., J. H. Crawford, M. M. Kleb, V. S. Connors, R. J. Bendura, J. L. Raper, G. W. Sachse, J. C. Gille, L. Emmons, and C. L. Heald (2003), Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft mission: Design, execution, and first results, Journal of Geophysical Research (Atmospheres), 108, 9000, doi:10.1029/2002JD003276.
The NASA Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft mission was conducted in February-April 2001 over the NW Pacific (1) to characterize the Asian chemical outflow and relate it quantitatively to its sources and (2) to determine its chemical evolution. It used two aircraft, a DC-8 and a P-3B, operating out of Hong Kong and Yokota Air Force Base (near Tokyo), with secondary sites in Hawaii, Wake Island, Guam, Okinawa, and Midway. The aircraft carried instrumentation for measurements of long-lived greenhouse gases, ozone and its precursors, aerosols and their precursors, related species, and chemical tracers. Five chemical transport models (CTMs) were used for chemical forecasting. Customized bottom-up emission inventories for East Asia were generated prior to the mission to support chemical forecasting and to serve as a priori for evaluation with the aircraft data. Validation flights were conducted for the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument and revealed little bias (6 +/- 2%) in the MOPITT measurements of CO columns. A major event of transpacific Asian pollution was characterized through combined analysis of TRACE-P and MOPITT data. The TRACE-P observations showed that cold fronts sweeping across East Asia and the associated warm conveyor belts (WCBs) are the dominant pathway for Asian outflow to the Pacific in spring. The WCBs lift both anthropogenic and biomass burning (SE Asia) effluents to the free troposphere, resulting in complex chemical signatures. The TRACE-P data are in general consistent with a priori emission inventories, lending confidence in our ability to quantify Asian emissions from socioeconomic data and emission factors. However, the residential combustion source in rural China was found to be much larger than the a priori, and there were also unexplained chemical enhancements (HCN, CH3Cl, OCS, alkylnitrates) in Chinese urban plumes. The Asian source of CCl4 was found to be much higher than government estimates. Measurements of HCN and CH3CN indicated a dominant biomass burning source and ocean sink for both gases. Large fractions of sulfate and nitrate were found to be present in dust aerosols. Photochemical activity in the Asian outflow was strongly reduced by aerosol attenuation of UV radiation, with major implications for the concentrations of HOx radicals. New particle formation, apparently from ternary nucleation involving NH3, was observed in Chinese urban plumes.
Lamarque, J.-F., and J. C. Gille (2003), Improving the modeling of error variance evolution in the assimilation of chemical species: Application to MOPITT data, Geophysical Research Letters, 30(9), n/a–n/a, doi:10.1029/2003GL016994.
This study focuses on improvement to the modeling of the evolution of the model error variance in the problem of assimilating satellite observations of chemical species. The model error variance evolution equation for the assimilation of CO is described here with localized sources in addition to transport and error growth. The assimilation of carbon monoxide (CO) observations from MOPITT is performed using a sub-optimal Kalman filter in the MOZART-2 chemistry-transport model. It is shown that this new approach can dramatically improve the ability of the assimilation to diverge from erroneous model-generated features.
Lamarque, J.-F., D. P. Edwards, L. K. Emmons, J. C. Gille, O. Wilhelmi, C. Gerbig, D. Prevedel, M. N. Deeter, J. Warner, D. C. Ziskin, B. Khattatov, G. L. Francis, V. Yudin, S. Ho, D. Mao, J. Chen, and J. R. Drummond (2003), Identification of CO plumes from MOPITT data: Application to the August 2000 Idaho-Montana forest fires, Geophysical Research Letters, 30(13), n/a–n/a, doi:10.1029/2003GL017503.
This study focuses on the identification of carbon monoxide (CO) released during the forest fires that took place primarily in Montana and Idaho during the summer of 2000. We focus our analysis on the most intense period of the fires during the second half of August. During that period, the MOPITT instrument onboard the EOS-Terra platform collected extensive measurements of CO. A simulation of the dispersal of the CO from the fires, constrained by the AVHRR observations of fire location and extent, clearly identifies the affected regions. The model results are compared with the CO observations from the COBRA experiment flight on August 19. Using these various data, we are able to identify the transport of the CO plume originating from the fires. In particular, it is shown that the CO travels eastward from the fires, reaching as far as the East coast and the Gulf of Mexico in a few days. Although the distribution of CO over the U.S. is clearly a combination of a variety of sources it is found that wildfires are a strong component of the summer tropospheric CO.


Clerbaux, C., J. Hadji-Lazaro, S. Payan, C. Camy-Peyret, J. Wang, D. P. Edwards, and M. Luo (2002), Retrieval of CO from nadir remote-sensing measurements in the infrared by use of four different inversion algorithms, Appl. Opt., 41(33), 7068–7078, doi:10.1364/AO.41.007068.
Four inversion schemes based on various retrieval approaches (digital gas correlation, nonlinear least squares, global fit adjustment, and neural networks) developed to retrieve CO from nadir radiances measured by such downward-looking satelliteborne instruments as the Measurement of Pollution in the Troposphere (MOPITT), the Tropospheric Emission Spectrometer (TES), and the Infrared Atmospheric Sounding Interferometer (IASI) instruments were compared both for simulated cases and for atmospheric spectra recorded by the Interferometric Monitor for Greenhouse Gases (IMG). The sensitivity of the retrieved CO total column amount to properties that may affect the inversion accuracy (noise, ancillary temperature profile, and water-vapor content) was investigated. The CO column amounts for the simulated radiance spectra agreed within 4%, whereas larger discrepancies were obtained when atmospheric spectra recorded by the IMG instrument were analyzed. The assumed vertical temperature profile is shown to be a critical parameter for accurate CO retrieval. The instrument’s line shape was also identified as a possible cause of disagreement among the results provided by the groups of scientists who are participating in this study.
Deeter, M. N., G. L. Francis, D. P. Edwards, J. C. Gille, E. McKernan, and J. R. Drummond (2002), Operational Validation of the MOPITT Instrument Optical Filters*, Journal of Atmospheric and Oceanic Technology, 19, 1772, doi:10.1175/1520-0426(2002)019<1772:OVOTMI>2.0.CO;2.
Optical bandpass filters in the Measurements of Pollution in the Troposphere (MOPITT) satellite remote sensing instrument selectivity limit the throughput radiance to absorptive spectral bands associated with the satellite-observed trace gases CO and CH4. Precise specification of the spectral characteristics of these filters is required to optimize retrieval accuracy. The effects and potential causes of spectral shifts in the optical bandpass filter profiles are described. Specifically, a shift in the assumed bandpass profile produces a relative bias between the calibrated satellite radiances and the corresponding values calculated by an instrument-specific forward radiative transfer model. Conversely, it is shown that the observed bias (as identified and quantified using operational MOPITT satellite radiance data) can be used to determine the relative spectral shift between the nominal (prelaunch) filter profiles and the true operational (in orbit) profiles. Revising both the radiance calibration algorithm and the forward radiative transfer model to account for the revised filter profiles effectively eliminates the radiance biases.


Warner, J. X., J. C. Gille, D. P. Edwards, D. C. Ziskin, M. W. Smith, P. L. Bailey, and L. Rokke (2001), Cloud Detection and Clearing for the Earth Observing System Terra Satellite Measurements of Pollution in the Troposphere (MOPITT) Experiment, Appl. Opt., 40(8), 1269–1284, doi:10.1364/AO.40.001269.
The Measurements of Pollution in the Troposphere (MOPITT) instrument, which was launched aboard the Earth Observing System (EOS) Terra spacecraft on 18 December 1999, is designed to measure tropospheric CO and CH4 by use of a nadir-viewing geometry. The measurements are taken at 4.7 μm in the thermal emission and absorption for the CO mixing ratio profile retrieval and at 2.3 and 2.2 μm in the reflected solar region for the total CO column amount and CH4 column amount retrieval, respectively. To achieve the required measurement accuracy, it is critical to identify and remove cloud contamination in the radiometric signals. We describe an algorithm to detect cloudy pixels, to reconstruct clear column radiance for pixels with partial cloud covers, and to estimate equivalent cloud top height for overcast conditions to allow CO profile retrievals above clouds. The MOPITT channel radiances, as well as the first-guess calculations, are simulated with a fast forward model with input atmospheric profiles from ancillary data sets. The precision of the retrieved CO profiles and total column amounts in cloudy atmospheres is within the expected ∓10% range. Validations of the cloud-detecting thresholds with the moderate-resolution imaging spectroradiometer airborne simulator data and MOPITT airborne test radiometer measurements were performed. The validation results showed that the MOPITT cloud detection thresholds work well for scenes covered with more than 5–10% cloud cover if the uncertainties in the model input profiles are less than 2 K for temperature, 10% for water vapor, and 5% for CO and CH4.


Edwards, D. P., and G. L. Francis (2000), Improvements to the correlated-k radiative transfer method: Application to satellite infrared sounding, Journal of Geophysical Research: Atmospheres, 105(D14), 18135–18156, doi:10.1029/2000JD900131.
This paper presents a new radiative transfer model based on the correlated-k technique that is particularly suitable for applications associated with broadband infrared satellite remote sounding of the atmosphere. We describe new developments to the approach which improve the accuracy of correlated-k distribution radiative transfer calculations. These include methods to model an instrument response function, spectral line overlap for multiple gases, and the spectral variation of solar and thermal source functions. We also describe an approach to improving vertical spectral correlation along ray paths through a nonhomogeneous atmosphere. For a radiative transfer model to be efficient as the forward model of a retrieval scheme, the calculation of analytical Jacobians is particularly important. This is implemented in the model using a variation on the correlated-k approach. The application of the new model, RADCKD, is demonstrated with example calculations for the EOS Terra satellite Measurements of Pollution in the Troposphere (MOPITT) instrument.
Wang, J., J. C. Gille, H. E. Revercomb, and V. P. Walden (2000), Validation Study of the MOPITT Retrieval Algorithm: Carbon Monoxide Retrieval from IMG Observations during WINCE, Journal of Atmospheric and Oceanic Technology, 17(10), 1285–1295, doi:10.1175/1520-0426(2000)017<1285:VSOTMR>2.0.CO;2.
The Measurement of Pollution in the Troposphere (MOPITT) instrument is an eight-channel gas correlation radiometer selected for the Earth Observing System (EOS) Terra spacecraft launched in December 1999. Algorithms for the retrieval of tropospheric carbon monoxide (CO) profiles from MOPITT measurements have been developed. In this paper, validation studies of the MOPITT CO retrieval algorithm using observations by the Interferometric Monitor for greenhouse Gases (IMG) during the Winter Clouds Experiment (WINCE) conducted from 23 January to 13 February 1997 are described. Synthetic radiance spectra calculated by a line-by-line radiative transfer model, FASCOD3, using the retrieved CO profile agrees well with IMG-measured radiance spectra. Observations by the Moderate Resolution Imaging Spectrometer (MODIS) Airborne Simulator (MAS) from the NASA ER-2 platform during WINCE were successfully used to assist in the identification of clear and cloudy IMG observations.


Beiying, W., and J. Gille (1999a), Retrieval of tropospheric co profiles using correlation radiometer: I. retrieval experiments for a clear atmosphere, Adv. Atmos. Sci., 16(3), 343–354, doi:10.1007/s00376-999-0013-4.
This paper discusses the retrieval scheme associated with the gas correlated radiometer MOPITT which will be on board of EOS-AM1 to measure the global vertical profiles of carbon monoxide. The vertical resolution and retrieval errors caused by errors in the temperature profiles and in the surface temperature have been assessed. The main results are: Assuming the noise equivalent radiance (NER) of 1.8 × 105 W m-2 sr-1, the surface temperature can be deduced from the wide band signals with uncertainty less than 1 K, and the atmospheric term of the modulated signal can be deduced with errors almost equal to the NER which does not significantly increase errors in the retrieved CO profiles. With typical uncertainty in temperature profiles, errors in the retrieved profiles at latitudes lower than 70‡ are generally less than 20% with the first guess of 100 ppbv. (If a better first guess was used, the errors may decrease). By incorporating the total column CO amount derived from the reflected solar radiation in 2.3 Μm spectral region into the retrieval, the accuracy of the retrieved CO profile below 6 km may be greatly improved. In the retrieval experiment with 10 CO profiles representing the typical CO profiles, the r.m.s. relative/ absolute errors of the retrieved CO profiles are about 10% / 15-20 ppbv.
Beiying, W., and J. Gille (1999b), Retrieval of tropospheric co profiles using correlation radiometer. ii: effects of other gases and the retrieval in cloudy atmosphere, Adv. Atmos. Sci., 16(4), 507–522, doi:10.1007/s00376-999-0027-y.
The effects of methane, ozone, water vapor and nitrous oxide on the retrieval of tropospheric CO profiles using correlation radiometer have been assessed. The scheme of the retrieval in the presence of solid clouds have been proposed. The effect of methane and nitrous oxide can be well accounted by their mean profile, and that of ozone can be represented by a typical middle latitude ozone profile, while for water vapor, less than 50% uncertainty is required. With the assumption of blackbody for cloud surface, the CO profile may be retrieved for low and middle solid clouds. However, the retrieval of CO profile will lose quality for high clouds.
Edwards, D. P., C. M. Halvorson, and J. C. Gille (1999), Radiative transfer modeling for the EOS Terra satellite Measurement of Pollution in the Troposphere (MOPITT) instrument, Journal of Geophysical Research: Atmospheres, 104(D14), 16755–16775, doi:10.1029/1999JD900167.
This paper describes the radiative transfer modeling effort in support of the EOS Measurements of Pollution in the Troposphere (MOPITT) instrument. MOPITT is due to be launched on the AM-1 Terra platform in the summer of 1999 and is a nadir-viewing gas correlation radiometer designed to measure CO and CH4 in the troposphere using a CO thermal channel at 4.7 μm and reflected solar channels for CO at 2.3 μm and CH4 at 2.2 μm. We describe the spectroscopic considerations and radiative transfer studies that have been performed for this instrument and the implications for operational algorithm design. We outline the construction of MOPITT project forward models, both the research codes and the fast transmittance module that forms part of the operational retrieval algorithm. Several different approaches have been considered for these models: full line-by-line calculations using the general purpose line-by-line transmittance and radiance model GENLN2, absorption coefficient look-up tables, and regression techniques using a recurrence parameterization of transmittance. These models are capable of reproducing MOPITT channel signals and their dependence on temperature, viewing geometry, and the mixing ratios of target and contaminating gases.
Wang, J., J. C. Gille, P. L. Bailey, J. R. Drummond, and L. Pan (1999a), Instrument Sensitivity and Error Analysis for the Remote Sensing of Tropospheric Carbon Monoxide by MOPITT, Journal of Atmospheric and Oceanic Technology, 16(4), 465–474, doi:10.1175/1520-0426(1999)016<0465:ISAEAF>2.0.CO;2.
Measurement of Pollution in the Troposphere (MOPITT) is an eight-channel gas correlation radiometer selected for the Earth Observing System AM-1 platform to be launched in 1999. Its primary objectives are the measurement of tropospheric carbon monoxide (CO) and methane (CH sub(4)). In this paper, the sensitivities of instrument signals and CO retrieval errors to various instrument parameters, especially the gas cell pressure and temperature variations, instrument radiometric noise, and ancillary data errors (such as atmospheric temperature and water vapor profile errors), are presented and discussed. In the MOPITT pressure modulator cell pressure sensitivity study, the instrument calibration process is considered, which leads to the relaxation of previous stringent requirements on the accuracy of in-orbit cell pressure monitoring. The approach of MOPITT CO retrieval error analysis is described, and the error analysis results are compared with retrieval simulation statistics. The error analysis results indicate that tropospheric CO distributions can be retrieved with a precision of 10% for most of the troposphere.
Wang, J., J. C. Gille, P. L. Bailey, L. Pan, D. Edwards, and J. R. Drummond (1999b), Retrieval of Tropospheric Carbon Monoxide Profiles from High-Resolution Interferometer Observations: A New Digital Gas Correlation (DGC)Method and Applications, Journal of the Atmospheric Sciences, 56(2), 219–232, doi:10.1175/1520-0469(1999)056<0219:ROTCMP>2.0.CO;2.
Global tropospheric carbon monoxide (CO) distributions can be retrieved from observations by spaceborne gas correlation radiometers and high-resolution interferometers. The Measurement of Pollution in the Troposphere (MOPITT) is a gas correlation radiometer designed for tropospheric CO and CH4 remote sensing. It is being developed at the University of Toronto and the National Center for Atmospheric Research for launch on the EOS/AM-1 platform in 1999. Spaceborne high-resolution interferometers with troposphere CO remote sensing capability include the Interferometric Monitor for Greenhouse gases (IMG) instrument and the Troposphere Emission Spectrometer (TES). IMG was developed by the Ministry of International Trade and Industry (MITI) of Japan. It was on the ADEOS-1 spacecraft launched in October 1996. TES is being developed by the Jet Propulsion Laboratory for launch on the EOS/CHEM-1 platform in 2002.For the purpose of testing the MOPITT data processing algorithms before launch, a new digital gas correlation (DGC) method was developed. This method makes it possible to use existing IMG observations to validate the MOPITT retrieval algorithms. The DGC method also allows the retrieval of global troposphere CO from MOPITT, IMG, and TES observations with a consistent algorithm. The retrieved CO profiles can be intercompared, and a consistent long time series of tropospheric CO measurements can be created. In this paper, the DGC method is described. The procedures for using the DGC method to retrieve atmospheric trace species profiles are discussed. As an example, CO profiles from IMG observations have been retrieved with the DGC method as a demonstration of its feasibility and application in MOPITT retrieval algorithm validation.


Pan, L., J. C. Gille, D. P. Edwards, P. L. Bailey, and C. D. Rodgers (1998), Retrieval of tropospheric carbon monoxide for the MOPITT experiment, Journal of Geophysical Research: Atmospheres, 103(D24), 32277–32290, doi:10.1029/98JD01828.
A retrieval method for deriving the tropospheric carbon monoxide (CO) profile and column amount under clear sky conditions has been developed for the Measurements of Pollution In The Troposphere (MOPITT) instrument, scheduled for launch in 1998 onboard the EOS-AM1 satellite. This paper presents a description of the method along with analyses of retrieval information content. These analyses characterize the forward measurement sensitivity, the contribution of a priori information, and the retrieval vertical resolution. Ensembles of tropospheric CO profiles were compiled both from aircraft in situ measurements and from chemical model results and were used in retrieval experiments to characterize the method and to study the sensitivity to different parameters. Linear error analyses were carried out in parallel with the ensemble experiments. Results of these experiments and analyses indicate that MOPITT CO column measurements will have better than 10% precision, and CO profile measurement will have approximately three pieces of independent information that will resolve 3–5 tropospheric layers to approximately 10% precision. These analyses are important for understanding MOPITT data, both for application of data in tropospheric chemistry studies and for comparison with in situ measurements.


Smith, M. W. (1997), Method and results for optimizing the MOPITT methane bandpass, Appl. Opt., 36(18), 4285–4291, doi:10.1364/AO.36.004285.
The Measurements of Pollution in the Troposphere (MOPITT) instrument will measure carbon monoxide and total column methane in the Earth’s atmosphere by means of gas-filter correlation radiometry. The center, width, and shape of the bandpass filters used to isolate the spectral channels must maximize the signal level and sensitivity to the gas of interest and minimize the interference from other absorbing gases (notably water vapor). I calculated the sensitivity to methane and the interference from other gases as a function of filter center and width. A slight shift in the filter parameters from the MOPITT baseline values increases the methane sensitivity by 20% and decreases the water vapor interference to 6% of its baseline value.


Pan, L., D. P. Edwards, J. C. Gille, M. W. Smith, and J. R. Drummond (1995), Satellite remote sensing of tropospheric CO and CH4: forward model studies of the MOPITT instrument, Appl. Opt., 34(30), 6976–6988, doi:10.1364/AO.34.006976.
The Measurements of Pollution in the Troposphere (MOPITT) instrument is designed to measure tropospheric CO and CH4 from a spaceborne platform by the use of infrared gas correlation radiometers. We describe the forward model that is used as the basis for the retrieval algorithm. We present the techniques used to model the instrument and describe the radiative transfer involved in the measurement process. Calculations have been performed to assess the sensitivity of the measured radiance to changes in the target-gas concentration profiles, changes in the concentration of contaminating constituents, and to variations in the parameters that describe reflection and emission of radiation at the Earth’s surface.

Publication Count by Year

1995 1
1997 1
1998 1
1999 5
2000 2
2001 1
2002 2
2003 6
2004 14
2005 6
2006 12
2007 10
2008 4
2009 6
2010 11
2011 7
2012 11
2013 17
2014 10
2015 11
2016 7
2017 9
2018 9
Compiled on 28 November 2018




ACOM | Atmospheric Chemistry Observations & Modeling