Abstract
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 and magnitude of and variation in SJV aerosols during the cold season. However, aerosols are not well represented in the 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 and precipitation that is represented better in the 4 km simulation. In rural areas, the model sensitivity to grid size is rather small. Our observational analysis reveals that dust is a primary contributor to aerosols in the SJV, especially during the warm season. Aerosol simulations in the warm season are sensitive to the parameterization of dust emission in WRF-Chem. 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 based on CALIPSO (Cloud-Aerosol Lidar and Infrared pathfinder Satellite Observation) aerosol extinction profiles. Improved representation of dust emission and vertical mixing in the boundary layer is needed for better simulations of aerosols during the warm season in the SJV.
Highlights
The San Joaquin Valley (SJV) in the southern portion of the California Central Valley is surrounded by a coastal mountain range to the west and the Sierra Nevada range to the east
Version 3 Level 2 532 nm aerosol extinction profiles derived from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) backscatter profiles collected onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite are used (Omar et al, 2009; Young and Vaughan, 2009)
The WRF-Chem (Weather Research and Forecasting model with Chemistry) model is employed to simulate the seasonal variability in aerosols in water year of 2013 (WY2013) in the San Joaquin Valley (SJV)
Summary
The San Joaquin Valley (SJV) in the southern portion of the California Central Valley is surrounded by a coastal mountain range to the west and the Sierra Nevada range to the east. Wu et al.: WRF-Chem simulation of aerosol seasonal variability in the SJV errors in regional-scale modeling of aerosol properties They include (1) emission sources, (2) meteorological parameterizations, (3) representation of aerosol chemistry, (4) limited understanding of the formation processes of secondary organic aerosol (SOA), (5) spatial resolution and (6) boundary conditions. This study will investigate the sensitivity of aerosol simulations to horizontal resolution and identify optimal model physical choices for reasonable representation of aerosol variabilities in the SJV. Another application of air quality modeling is to provide initial a priori fields for remote sensing retrievals.
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