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Multiscale Modeling of Multi-decadal Trends in Ozone across the Northern Hemisphere & United States
Citation:
Mathur, R., J. Xing, S. Napelenok, AND C. Hogrefe. Multiscale Modeling of Multi-decadal Trends in Ozone across the Northern Hemisphere & United States. 34th International Technical Meeting on Air Pollution Modelling and its Application, Montpellier, FRANCE, May 04 - 08, 2015.
Impact/Purpose:
The National Exposure Research Laboratory’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.
Description:
Both observational and modeling studies have demonstrated that pollutants near the Earth’s surface can be convectively lofted to higher altitudes where strong winds can efficiently transport them from one continent to another, thereby impacting air quality on intercontinental to global scales. Thus, strategies for reduction of pollution levels of surface air over a region are complicated not only by the interplay of local emissions sources and several complex physical, chemical, dynamical processes in the atmosphere, but also hemispheric background levels of pollutants. To assist with the design of emission control strategies that yield compliance with more stringent air quality standards, models must possess the fidelity to accurately simulate ambient pollutant levels across the entire spectrum ranging from background to extreme concentrations. Consistent modeling frameworks that can represent the interactions between various physical and chemical atmospheric processes at the disparate space and time scales are thus needed. Multi-decadal model calculations for the 1990-2010 period are performed with the coupled WRF-CMAQ modeling system over a domain encompassing the northern hemisphere and a nested domain over the continental U.S. Simulated trends in ozone and precursor species concentrations across the U.S. over the past two decades are compared with those inferred from available measurements during this period. The impact of model grid resolution on capturing the spatial variability in trends in surface ozone levels is investigated. The Decoupled Direct Method (DDM) sensitivity analysis technique is employed in model calculations to help identify the relative contribution of different source-region contributions to ozone levels in the U.S.
