Air pollution is a major societal and environmental threat that is occurring in many places across the world including Central Asia (CA). Yet this region is significantly understudied, which motivated Janyl Madykova to make this a topic for her research. Janyl is from Kyrgyzstan and came to the USA in 2018 as a Fulbright Scholar. In summer 2020 she virtually visited NCAR under a Muskie Internship Program collaborating with ACOM on exploring air quality in CA. Here is a brief summary of the work Janyl performed.

A continental-scale plume of carbon monoxide (CO) and other air pollutants from active fires in Siberia is being mapped in near real-time by ACOM scientists, based on data provided by TROPOMI (the TROPOspheric Monitoring Instrument, on board ESA's Sentinel-5P platform). Figures 1 and 2 illustrate the magnitude of CO emissions during this fire season (summer 2019) compared to the same period last year (2018).

Wildfires tend to be more intense and hence costly and are predicted to increase in frequency under a warming climate. For example, the recent August 2015 Washington State fires were the largest in the state’s history. Such large fires impact not only the local environment but also affect air quality far downwind through the long-range transport of pollutants. Global to continental scale coverage showing the evolution of CO resulting from fire emission is available from satellite observations.

A multitude of recent atmospheric observations show that organic aerosols are ubiquitous and often more abundant than other particles such as sulfate, nitrate, soot, and dust.  These large amounts of organic particles contribute to the health impacts of air pollution, to regional visibility reductions, to both cooling and warming tendencies of radiative forcing, and to modified cloud properties and precipitation patterns.  Uncertainties remain in all aspect of their lifecycle, i.e., their formation, transformations and properties, and especially their removal.

Secondary organic aerosol (SOA) production in urban and biogenic outflow was investigated using the explicit gas-phase chemical mechanism generator GECKO-A [Lee-Taylor et al., 2015]. Urban outflow simulations show several-fold increases in SOA mass continuing for multiple days, whereas forest outflow simulations showed only modest SOA mass increases, and no long-term growth. The multiday SOA production in urban-origin air stems from multigenerational oxidation products of gas-phase precursors which persist in equilibrium with the particle phase.

Current analysis of the FTS (Fourier Transform Spectrometer) NCAR / NDACC  (Network for the Detection for Atmospheric Composition Change) data show secular increases in several species.  Focusing on HCl, the largest reservoir of chlorine in the stratosphere due to reduced emissions through the 1990's the total column amounts were observed to be decreasing starting in 1997-1998 [Rinsland et al, 2003].   This was until about 2007 when that trend appeared to be reversing.  Now with the benefit of several years of observations the secular increase is quite evident.  Fig 1.

ACD scientists in collaboration with colleagues from seven universities successfully sampled atmospheric composition over the Western Pacific warm pool region during the season characterized by massive convective storms.  The CONvective TRansport of Active Species in the Tropics (CONTRAST) experiment successfully concluded its field phase during January-February 2014. 

Secondary Organic Aerosol (SOA) formation in aqueous particles

Recent research suggests that in-cloud and in-particle chemistry could contribute substantially to the formation of SOA. Glyoxal is one of the precursors proposed to be important. In Knote et al. (2013) we included the state of knowledge on SOA formation from glyoxal into WRF-chem and conducted simulations over California as well as the continental United States for summer 2010.

A regional nuclear conflict between India and Pakistan would not only inflict immediate damage in the subcontinent, including massive loss of life and destruction of built infrastructure; severe long-term environmental damage would also spread globally, lasting decades, researchers have found.

HIRDLS observations have shown a strong increase in gravity wave momentum flux (MF) in the stratosphere as a result of deep convection due to the monsoons. Annualised measurements of GW MF from HIRDLS (Figure 1, top) show a strong positive correlation with rainfall (blue line) and a strong anticorrelation with outgoing longwave radiation (green line), a standard proxy for convective activity. Measurements suggest that the Indian monsoon leads to a 25% increase in the measured momentum flux levels in this region, with half the annual total MF generated during the monsoon season.

The composition and magnitude of volcanic gas emissions contain keys to understanding and predicting volcanic events. Additionally, some volcanic gases have a positive radiative forcing and thus impact climate. Volcanic gases are mostly analyzed in situ or using airborne instruments, with all the consequent limitations in safety and sampling, and at elevated costs.

Accurate NOx emissions are essential for air pollution quantification and mitigation. Combustion processes in the transportation, industrial, and residential sector and emissions from power plants are the dominant anthropogenic sources of NOx. In addition to contributing to the formation of ground-level ozone and fine particle pollution, high levels of NOx are linked with a number of adverse effects on the respiratory system.

The NCAR CESM system is facilitating the investigation of the interactions among different components of the earth-atmospheric system. One of the available atmospheric models is WACCM, which was specifically developed to simulate interactions between chemistry and climate across all levels of the atmosphere. WACCM simulations are particularly valuable in exploring the impact of middle atmosphere dynamics and chemistry on the climate system.

In collaboration with researchers from the State University of New York’s College of Environmental Science and Forestry in Syracuse, ACD scientists have measured the fractionation of deuterated methoxy radicals, CH₂DO, which are formed in the atmospheric oxidation of methane. Methane, CH₄, is the most-abundant hydrocarbon in the atmosphere, as a result of its large source strength and low rate of reaction with OH radicals. Its oxidation provides a global background sink for OH and a source of CO.

Photochemical smog is a byproduct of the NOx-catalyzed oxidation of volatile organic compounds (VOCs) under solar ultraviolet (UV) radiation.  While the chemical regime can be NOx-limited, VOC-limited, or NOx-inhibited, it is always photon limited and therefore sensitive to changes in the UV radiation field.  In polluted regions, these radiation changes can be caused by the smog itself, especially ozone (O₃), nitrogen dioxide (NO₂), and aerosol particles.

The new Version 5 (“V5”) MOPITT (Measurements of Pollution in the Troposphere) product for carbon monoxide (CO) is the first satellite product to exploit simultaneous near-infrared (NIR) and thermal-infrared (TIR) observations to enhance retrieval sensitivity in the lower troposphere. Since most major sources of tropospheric CO are found at or near the Earth's surface, this feature will improve air quality forecasts and studies of CO sources.

The extratropical upper troposphere and lower stratosphere (Ex‐UTLS) is a transition region between the stratosphere and the troposphere. In this region, dynamics, chemistry, clouds and radiation are strongly coupled, which makes this region important for chemistry-climate interactions. Significant progress has been made in understanding the climate-relevant processes in this region during the last decade, assisted by a suite of new observational studies.

A new ozonesonde climatology for the period 1995-2009 was compiled for model evaluation and comparison to other observations [Tilmes et al., 2011]. This climatology allows evaluating the performance of ozone especially in the troposphere and lower stratosphere. Various models still show significant shortcomings to reproduce the structure and seasonality of ozone, one of the most important trace gases in the atmosphere.

New particle formation, the spontaneous creation of new nanometer-sized particles in the atmosphere, is often the dominant source of particles in remote regions. A major part of newly formed aerosol consists of organic material that can be attributed to photo-chemically reacted volatile organic compounds emitted by vegetation. Understanding the mechanisms responsible for the growth of these biogenic nanoparticles into sizes where they may scatter radiation efficiently or change cloud properties is vitally important for assessing the impacts of new particle formation on climate.

The tropopause is a fundamental boundary of the atmosphere, separating the turbulent mixing dominated troposphere from the much more stable and stratified stratosphere. To examine the role of the tropopause and the jet streams in constraining the cloud distributions, ACD scientists performed an analysis of cloud top and tropopause relationships using the Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) cloud data and National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) tropopause data.

The importance of lateral boundary conditions (BC) in regional atmospheric transport models or numerical prediction models has been well established in the meteorological community. Much more recently, attention has also been drawn to the consideration of chemical lateral boundary conditions in regional chemical transport models (CTMs) and in air quality simulations, and the importance of the inflow of pollution on local air quality.

The vertical depths of cirrus in the upper troposphere vary from less to a kilometer to many kilometers. There is interest in knowing these depths in order to understand how cirrus contributes to the heating and cooling rates in the upper troposphere – a positive solar plus infrared heating rate will impart a positive enhancement to the vertical motion field. Measurements of cirrus by the HIRDLS experiment add to our knowledge base, since the HIRDLS experiment is sensitive to the presence of small amounts of cirrus along limb-views in the upper troposphere.

The global chemical transport model MOZART-4 has been recently released to the scientific community through the ACD MOZART-4 homepage and the NCAR Community Data Portal. The description of MOZART-4 has been submitted to the online journal Geoscientific Model Development [Emmons et al., 2009].

The MOPITT team has made significant advances in demonstrating multispectral retrievals of CO (carbon monoxide) with enhanced sensitivity to near-surface CO. MOPITT, (Measurements Of Pollution In The Troposphere), on EOS-Terra, has been measuring CO since March 2000, and is the only satellite instrument with both thermal infrared (TIR) and near infrared (NIR) CO channels. The standard MOPITT V4 product uses TIR-only radiances to produce CO distributions for day/night, ocean/land observations.

The mechanisms by which secondary organic aerosols (SOA) form in the atmosphere are a topic of much current research. Parameterizations used in air quality and climate have difficulty reproducing observed quantities of ambient aerosol, at least in part because of their inability to account for the diversity of chemical species involved in SOA formation.