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Constraining U.S. ammonia emissions using TES remote sensing observations and the GEOS-Chem adjoint model
Citation:
Zhu, L., D. Henze, K. Cady-Pereira, M. Shephard, M. Luo, R. Pinder, J. Bash, AND G. Jeong. Constraining U.S. ammonia emissions using TES remote sensing observations and the GEOS-Chem adjoint model. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES. American Geophysical Union, Washington, DC, 118(8):3355-3368, (2013).
Impact/Purpose:
The National Exposure Research Laboratory′s (NERL′s) Atmospheric Modeling and Analysis 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.
Description:
Ammonia (NH(3)has significant impacts on biodiversity, eutrophication, and acidification. Widespread uncertainty in the magnitude and seasonality of NH3 emissions hinders efforts to address these issues. In this work, we constrain U.S. NH3 sources using observations from the TES satellite instrument with the GEOS-Chem model and its adjoint. The inversion framework is first validated using simulated observations. We then assimilate TES observations for April, July, and October of 2006 through 2009. The adjoint-based inversion allows emissions to be adjusted heterogeneously; they are found to increase in California throughout the year, increase in different regions of the West depending upon season, and exhibit smaller increases and occasional decreases in the Eastern U.S. Evaluations of the inversion using independent surface measurements show reduced model underestimates of surface NH3 and wet deposited NHx in April and October; however, the constrained simulation in July leads to overestimates of these quantities, while TES observations are still under predicted. Modeled sulfate and nitrate aerosols concentrations do not change significantly, and persistent nitrate overestimation is noted, consistent with previous studies. Overall, while satellite-based constraints on NH3 emissions improve model simulations in several aspects, additional assessment at higher horizontal resolution of spatial sampling bias, nitric acid formation, and diurnal variability and bi-directionality of NH3 sources may be necessary to enhance year-round model performance across the full range of gas and aerosol evaluations.
URLs/Downloads:
VERSION SENT TO THE JOURNAL AFTER INTERNAL REVIEW.PDF (PDF, NA pp, 5978.927 KB, about PDF)Journal of Geophysical Research - Atmospheres
