WRF-Chem simulation of aerosol seasonal variability in the San Joaquin Valley
Longtao Wu1, Hui Su1, Olga V. Kalashnikova1, Jonathan H. Jiang1, Chun Zhao2, Michael J. Garay1, James R. Campbell3, and Nanpeng Yu41Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA 2Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, USA 3Naval Research Laboratory, Monterey, CA, USA 4University of California, Riverside, Riverside, CA, USA
Received: 04 Nov 2016 – Accepted for review: 23 Nov 2016 – Discussion started: 29 Nov 2016
Abstract. 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 km resolution than at 20 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., Campbell, J. R., and Yu, N.: WRF-Chem simulation of aerosol seasonal variability in the San Joaquin Valley, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-981, in review, 2016.