Improved retrieval of aerosol optical depth from MODIS measurements over the Pearl River delta region

An improved aerosol retrieval method based on the Moderate Resolution Imaging Spectroradiometer (MODIS) dark target algorithm was introduced to retrieve the aerosol properties over the Pearl River Delta (PRD) region. Empirical relationships between visible and shortwave infrared bands were built based on the regression analysis of MODIS surface reflectance products at a spatial resolution of 500m over the PRD region, so as to separate surface contributions from satellite-measured signals. In addition, local representative aerosol types for the PRD region were derived based on the statistics of ground-based Aerosol Robotic Network observations. The validation result showed that the newly derived 500m aerosol optical depth (AOD) product had a slight performance advantage over MODIS 10km and 3km aerosol products. It also had significantly better spatial coverage than the two MODIS aerosol products. The high spatial resolution aerosol products brought new information about distributions of aerosol sources, and they were much more suitable for the aerosol studies over the urban areas than the MODIS aerosol products at a coarse resolution.