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Annual Application and Evaluation of the Online Coupled WRF‐CMAQ System over North America under AQMEII Phase 2
Citation:
Hogrefe, C., G. Pouliot, David-C Wong, A. Torian, S. Roselle, Jon Pleim, AND R. Mathur. Annual Application and Evaluation of the Online Coupled WRF‐CMAQ System over North America under AQMEII Phase 2. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 115:683-694, (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:
We present an application of the online coupled WRF-CMAQ modeling system to two annual simulations over North America performed under Phase 2 of the Air Quality Model Evaluation International Initiative (AQMEII). Operational evaluation shows that model performance is comparable to earlier annual applications of the uncoupled WRF/CMAQ modeling system. In particular, model performance for ozone, PM2.5 and PM10 was comparable to 2006 simulations performed under AQMEII Phase 1, but factors other than feedback effects and model updates, such as changes in the underlying emissions inventory and chemical boundary conditions, likely exert a larger influence on model performance than feedback effects. A comparison of the simulated Aerosol Optical Depth (AOD) against observations reveals a tendency toward underprediction in all seasons despite a tendency to overpredict PM2.5 during wintertime. Summertime sensitivity simulations without feedback effects are used to quantify the average impact of the simulated direct feedback effect on temperature, PBL heights, ozone and PM2.5 concentrations. Additional sensitivity simulations show that the nudging approach employed in this study improves performance for 2m temperature while it has only a small dampening effect on the strength of the simulated direct feedbacks. Model results for 2006 and 2010 are analyzed to compare modeled changes between these years to those seen in observations, an approach called “dynamic evaluation”. The results for summertime average daily maximum 8-hr ozone showed that the model tends to underestimates the observed decrease in concentrations. The results for total and speciated PM2.5 vary between quarters, networks and species, but the WRF-CMAQ simulations do capture the substantial deceases in observed PM2.5 concentrations in summer and fall. These 2010-2006 PM2.5 decreases result in simulated increases of clear-sky short wave radiation between 5 and 10 W/m2. The spatial pattern of the simulated radiation changes are broadly consistent CERES satellite data though WRF-CMAQ underestimates the magnitude of the CERES-derived change between 2006 and 2010. The WRF-CMAQ configuration without direct feedback effects simulates smaller changes in summertime PM2.5 concentrations, indicating that the direct feedback effect enhances the air quality benefits arising from emission controls and that coupled modeling systems are necessary to quantify such feedback effects.
URLs/Downloads:
HOGREFEETAL_AQMEII2_SI_REVISION_FINAL FINAL.PDF (PDF, NA pp, 1966.774 KB, about PDF)Atmospheric Environment
