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Dynamic evaluation of the CMAQv5.0 modeling system: Assessing the model’s ability to simulate ozone changes due to NOx emission reductions
Citation:
Foley, K., C. Hogrefe, G. Pouliot, S. Roselle, N. Possiel, H. Simon, AND B. Timin. Dynamic evaluation of the CMAQv5.0 modeling system: Assessing the model’s ability to simulate ozone changes due to NOx emission reductions. Chapter 71, 33rd ITM Air Pollution Modeling and Its Applications XXIII. Springer, New York, NY, , 433-438, (2014).
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:
Regional air quality models are frequently used for regulatory applications to predict changes in air quality due to changes in emissions or changes in meteorology. Dynamic model evaluation is thus an important step in establishing credibility in the model predicted pollutant response. Beginning in 2003, the U.S. Environmental Protection Agency required substantial reductions in NOx emissions from power plants in the eastern U.S. which resulted in a decrease in ozone concentrations at monitoring sites in this region. This observable change in air quality has been used previously as a case study for dynamic evaluation of the Community Multiscale Air Quality (CMAQ) modeling system. Evaluation studies of previous CMAQ versions have shown that the model predicted decrease in ozone from 2002 to 2005 is less than the observed ozone change in this region. In this study, summertime simulations of 2002 and 2005 were conducted using the CMAQ version 5.0 modeling system released in 2012 that included several model updates aimed at improving the model predicted response, including updates to important model inputs. “Cross” simulations were conducted to separate the modeled impact of the emissions changes on ozone concentrations from the changes attributable to differences in meteorology across these years. Results show the change in the upper end of the ozone distribution explained by emission reductions is similar in magnitude to the change in ozone due to changes in meteorology across these years. Overall, the observed ozone decrease in the eastern U.S. continues to be underestimated by the model at both urban and rural monitoring sites.
