Evaluation of Seasonal Simulations over Central California in the WRF-Chem

Seasonal simulations of the WRF-Chem model over Central California are evaluated using satellite and in-situ observations. Results show that the WRF-Chem model reproduces magnitude and seasonal variability of meteorological variables, such as precipitation and snowpack. Observations show that aerosol optical depth (AOD) over Central California has small seasonal variation while large seasonal variation is observed for different particle matter (PM) species. Large amount of PM2.5 (mainly NO₃ and OC) are observed in the cold seasons (from October to March) while large particle dust is dominated in the warm seasons (from April to September). The WRF-Chem model can reproduce magnitude and seasonal variation of aerosol and aerosol speciation, but sensitivity to horizontal resolution and dust emission parameterization. In the cold seasons, the 4 km simulations well represent the magnitude of AOD and aerosol masses for different species while 20 km simulations underestimate aerosols, mainly due to the horizontal resolution of anthropogenic emission data although the same data source is used. In the warm seasons, the model simulations are more sensitive to the dust emission parameterization. The GOCART/SORGAM dust scheme has significant low bias in simulating dust over Central California while the MOSAIC and MADE/SORGAM dust scheme has better agreement with observations.