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Geosci. Model Dev. Discuss., 2, 1081-1114, 2009
www.geosci-model-dev-discuss.net/2/1081/2009/ doi:10.5194/gmdd-2-1081-2009 © Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License. |
Sensitivity of the Community Multiscale Air Quality (CMAQ) Model v4.7 results for the eastern United States to MM5 and WRF meteorological drivers
Atmospheric Modeling and Analysis Division, National Exposure Research Laboratory, Office of Research and Development, US Environmental Protection Agency, RTP, NC 27711, USA
Abstract. This paper presents a comparison of the operational performances of two Community Multiscale Air Quality (CMAQ) model v4.7 simulations that utilize input data from the 5th-generation Mesoscale Model (MM5) and the Weather Research and Forecasting (WRF) meteorological models. Two sets of CMAQ model simulations were performed for January and August 2006. One set utilized MM5 meteorology (MM5-CMAQ) and the other utilized WRF meteorology (WRF-CMAQ), while all other model inputs and options were kept the same. For January, predicted ozone (O3) concentrations were higher in the Southeast and lower Mid-west regions in the WRF-CMAQ simulation, resulting in slightly higher bias and error as compared to the MM5-CMAQ simulations. The higher predicted O3 concentrations are attributed to less dry deposition of O3 in the WRF-CMAQ simulation due to differences in the calculation of the vegetation fraction between the MM5 and WRF models. The WRF-CMAQ results showed better performance for particulate sulfate (SO42−), similar performance for nitrate (NO3−) and total nitrate (TNO3), and slightly worse performance for total carbon (TC) and total fine particulate (PM2.5) mass than the corresponding MM5-CMAQ results. For August, predictions of O3 were notably higher in the WRF-CMAQ simulation, particularly in the southern United States, resulting in increased model bias. Concentrations of predicted particulate SO42− were lower in the region surrounding the Ohio Valley and higher along the Gulf of Mexico in the WRF-CMAQ simulation, contributing to poorer model performance. The primary cause of the differences in predicted concentrations between the MM5-CMAQ and WRF-CMAQ simulations is due to differences in the calculation of the friction velocity (u*) in MM5 and WRF models, which has a large effect on the dry deposition of NO, NO2 and HNO3. Differences in the calculation of the vegetation fraction and the predicted cloud cover, along with several other minor differences in the simulations also affect the predicted concentrations from CMAQ. The performance for SO42−, NO3− and NH4+ wet deposition was similar for both simulations for January and August.
Citation: Appel, K. W., Roselle, S. J., Gilliam, R. C., and Pleim, J. E.: Sensitivity of the Community Multiscale Air Quality (CMAQ) Model v4.7 results for the eastern United States to MM5 and WRF meteorological drivers, Geosci. Model Dev. Discuss., 2, 1081-1114, doi:10.5194/gmdd-2-1081-2009, 2009.