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There is significant public health interest in gaining a better understanding of the health effects associated with particulate matter (PM) of differing sizes and compositions. Unfortunately the PM monitoring data needed for such studies are limited. Satellite observations of aerosol optical depth (AOD) have been used to overcome this limitation, but existing techniques using AOD to estimate surface concentrations of PM have limited ability to differentiate particle size and type, and the spatial resolution is often too coarse to evaluate PM variability on local scales. Fortunately there has been a significant breakthrough in aerosol product from the Multi-angle Imaging SpectroRadiometer (MISR) instrument onboard the NASA Terra satellite. Recent computational advances have made it possible to derive a “local mode” MISR aerosol product at a spatial resolution of 4.4 km that maintains the quality of the 17.6 km resolution Version 22 operational aerosol product. MISR is uniquely capable of providing total AOD as well as AOD fractionated by size (small, medium, and large), enabling estimation of size-resolved surface PM concentrations. 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 PM 2.5 , PM 10 , and PM 2.5 chemical species over Southern California. We found, and confirmed by leave-one-site-out cross validation, that PM 2.5 was best estimated with a spatio-temporal model of AOD small + medium that also included adjustment for relative humidity and wind speed (R 2 = 0.67, CV R 2 = 0.51), while PM 10 was best estimated from AOD large with adjustment for dew point and wind speed (R 2 = 0.76, CV R 2 = 0.44). Total AOD was most strongly associated with PM 2.5 components SO 4 2 − (R 2 = 0.74, CV R 2 = 0.69) and NO 3 − (R 2 = 0.72, CV R 2 = 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. [ABSTRACT FROM AUTHOR]