A WRF sensitivity study for summer ozone and winter PM events in California

Friday, 19 December 2014
Zhan Zhao1, Jianjun Chen1, Abdullah Mahmud1, Pingkuan Di1, Jeremy Avise1,2, John DaMassa1 and Ajith P Kaduwela1,3, (1)California Air Resources Board, Sacramento, CA, United States, (2)Washington State University, Civil and Environmental Engineering, Pullman, WA, United States, (3)UC-Davis Air Quality Research Center, Davis, CA, United States
Elevated summer ozone and winter PM frequently occur in the San Joaquin Valley (SJV) and the South Coast Air Basin (SCAB) in California.  Meteorological conditions, such as wind, temperature and planetary boundary layer height (PBLH) play crucial roles in these air pollution events. Therefore, accurate representation of these fields from a meteorological model is necessary to successfully reproduce these air pollution events in subsequent air quality model simulations. California’s complex terrain and land-sea interface can make it challenging for meteorological models to replicate the atmospheric conditions over the SJV and SCAB during extreme pollution events. In this study, the performance of the Weather Research and Forecasting Model (WRF) over these two regions for a summer month (July 2012) and a winter month (January 2013) is evaluated with different model configurations and forcing.  Different land surface schemes (Pleim-Xiu vs. hybrid scheme), the application of observational and soil nudging, two SST datasets (the Global Ocean Data Assimilation Experiment (GODAE) SST vs. the default SST from North American Regional Reanalysis (NARR) reanalysis), and two land use datasets (the National Land Cover Data (NLCD) 2006 40-category vs. USGS 24-category land use data) have been tested.  Model evaluation will focus on both surface and vertical profiles for wind, temperature, relative humidity, as well as PBLH.  Sensitivity of the Community Multi-scale Air Quality Model (CMAQ) results to different WRF configurations will also be presented and discussed.