WRF-Chem simulations of aerosol seasonal variability in the San Joaquin Valley (SJV), California are evaluated by satellite and in-situ observations. Results show that the WRF-Chem model successfully captures the distribution, magnitude and variation of SJV aerosols in cold season. However, the aerosols are not well represented in warm season. Aerosol simulations in urban areas during the cold season are sensitive to model horizontal resolution, with better simulations at 4&thinsp;km resolution than at 20&thinsp;km resolution, mainly due to inhomogeneous distribution of anthropogenic emissions. In rural areas, the model sensitivity to grid size is rather small. Our observational analysis show that dust is a primary contributor to aerosols in the SJV, especially in the warm season. Aerosol simulations in the warm season are sensitive to parameterization of dust emission in the WRF-Chem model. The GOCART (Goddard Global Ozone Chemistry Aerosol Radiation and Transport) dust scheme produces very little dust in the SJV while the DUSTRAN (DUST TRANsport model) scheme overestimates dust emission. Vertical mixing of aerosols is not adequately represented in the model comparing to CALIPSO (Cloud-Aerosol Lidar and Infrared pathfinder Satellite Observation) aerosol extinction profiles. Improved representation of dust emission and vertical mixing are needed for better simulations of aerosols in warm season in the SJV. Aerosols generated by wild fires are not captured in the simulations with climatological fire emissions, underscoring the need of fire emission observations for operational usage.
Wu, L., Su, H., Kalashnikova, O. V., Jiang, J. H., Zhao, C., Garay, M. J., … Yu, N. (2017). WRF-Chem simulation of aerosol seasonal variability in the San Joaquin Valley. Atmospheric Chemistry and Physics, 17(12), 7291–7309. https://doi.org/10.5194/acp-17-7291-2017