Size-resolved particulate matter concentrations derived from 4.4Â km-resolution size-fractionated Multi-angle Imaging SpectroRadiometer (MISR) aerosol optical depth over Southern California

Total and size-fractionated AOD from the MISR 4.4 km aerosol product were used to develop spatio-temporal models to estimate surface concentrations of PM2.5, PM10, and PM2.5 chemical species over Southern California. We found, and confirmed by leave-one-site-out cross validation, that PM2.5 was best estimated with a spatio-temporal model of AOD small + medium that also included adjustment for relative humidity and wind speed (R2 = 0.67, CV R2 = 0.51), while PM10 was best estimated from AOD large with adjustment for dew point and wind speed (R2 = 0.76, CV R2 = 0.44). Total AOD was most strongly associated with PM2.5 components SO42 − (R2 = 0.74, CV R2 = 0.69) and NO3− (R2 = 0.72, CV R2 = 0.39). The best fitting models were applied to all available MISR aerosol retrievals over the region, generating surfaces of estimated size-resolved PM concentrations that will be a great asset to the environmental science and public health communities.