ACOM

Atmospheric Chemistry Observations & Modeling

Assessing the Impacts of Assimilating IASI and MOPITT CO Retrievals Using CESM/CAM-Chem and DART

The CESM-CAM-Chem/DART data assimilation system is used to investigate and assess the impact of assimilating CO retrieved profiles from two satellite instruments (IASI and MOPITT) on constraining the forecast and analysis of CO in CAM-Chem. The two instruments provide different and complementary capabilities in constraining CO. While the multispectral retrievals from MOPITT have enhanced sensitivity toward the surface and across the main CO source regions, its coverage is relatively limited.

Multiday production of SOA in urban and forest outflow

Regional pollution around Mexico City - photo by NASA

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.

Discovering the source of nanoparticles in Brazil’s Green Ocean

Research station in Tapajos National Forest

During certain times of the year, the atmosphere above Brazil’s Amazon Basin is so clean that it has prompted some scientists to refer to this region as the “Green Ocean.” Because its atmosphere is typically clean, changes in the atmosphere, such as the introduction of particles due to biomass burning or emissions of sulfur dioxide from power generators, can profoundly impact processes such as cloud formation, and thereby impact regional climate and precipitation.

Stratospheric chlorine species rising in the Arctic

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.

Projections of future summertime ozone over the U.S.

Regional chemistry-climate model simulations of present and future conditions were performed to assess changes in surface ozone in the summertime U.S. [Pfister et al., 2014].   The Nested Regional Climate Model with Chemistry (NRCM-Chem), based on WRF-Chem, was used to simulate, at high spatial resolution, the present and a 2050 future time period under the A2 climate and Representative Concentration Pathway (RCP) 8.5 anthropogenic precursor emission scenarios.

Using WACCM to investigate the influence of stratospheric ozone loss on trends in sea ice

WACCM logo

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.

Exploring Methane Oxidation Through Hydrogen Isotopes

Methane oxidation through hydrogen isotopes

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.

ACD Model Simulates Release of Pollen

Pollen distribution in Southern California

ACD scientists Tiffany Duhl and Alex Guenther have developed a model that simulates the release of wind-dispersed pollen from vegetation.  In collaboration with colleagues at the California Institute of Technology and Washington State University, they are using the model to address the question of how pollen occurrence may be affected by climate change and interact with anthropogenic pollutants to affect human health in a changing world.

Ultraviolet Radiation in Polluted Environments

Measured and calculated actinic flux

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.

MOPITT Multispectral CO Products Released

MOPITT satellite overpass on October 22, 2008.

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.

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