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Satellite observations of tropospheric ammonia and carbon monoxide: Global distributions, regional correlations and comparisons to model simulations
Luo, M., M. Shephard, K. Cady-Pereira, D. Henze, L. Zhu, J. Bash, R. Pinder, S. Capps, J. Walker, AND M. Jones. Satellite observations of tropospheric ammonia and carbon monoxide: Global distributions, regional correlations and comparisons to model simulations. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 106:262-277, (2015).
The National Exposure Research Laboratory's (NERL's)Atmospheric Modeling Division (AMAD) conducts research in support of EPA's mission to protect human health and the environment. AMAD's research program is engaged in developing and evaluating predictive atmospheric models on all spatial and temporal scales for forecasting the Nation's air quality and for assessing changes in air quality and air pollutant exposures, as affected by changes in ecosystem management and regulatory decisions. AMAD is responsible for providing a sound scientific and technical basis for regulatory policies based on air quality models to improve ambient air quality. The models developed by AMAD are being used by EPA, NOAA, and the air pollution community in understanding and forecasting not only the magnitude of the air pollution problem, but also in developing emission control policies and regulations for air quality improvements.
Ammonia (NH3) and carbon monoxide (CO) are primary pollutants emitted to the Earth's atmosphere from common as well as distinct sources associated with anthropogenic and natural activities. The seasonal and global distributions and correlations of NH3 and CO from the Tropospheric Emission Spectrometer (TES) satellite observations and GEOS-Chem model simulations for 2007 are investigated to evaluate how well the global and seasonal pollutant sources are prescribed in the model. Although the GEOS-Chem simulations of NH3 and CO atmospheric mixing ratio values are lower than the TES satellite observations, the global distribution patterns from the model reasonably agree with the observations, indicating that the model represents the general location of the source regions and the seasonal enhancements of NH3 and CO globally over large regional scales. In regions and seasons where biomass burning is the dominant source of both NH3 and CO emissions into the atmosphere, there are strong NH3:CO correlations, which is consistent with the relationship demonstrated by surface measurements over fires. In regions where the enhanced NH3 and CO are known to be produced by different sources, the NH3:CO correlations from TES observations and model simulations are weak or non-existent. For biomass burning regions the NH3:CO ratios are 0.015 (TES) and 0.013 (GEOS-Chem). In regions of high-population density, known heavy traffic, and limited biomass burning sources, such as the rapidly developing areas of South Asia and northern China, which include mixtures of megacities, industrial, and agricultural areas, the two species show weaker but still positive correlations and NH3:CO ratios of 0.051 (TES) and 0.036 (GEOS-Chem). These enhancement ratios of NH3 relative to CO are useful in constraining NH3 emission inventories when CO emission inventories are better known for some events or regions (i.e. biomass burning).