Improved retrieval of aerosol optical depth from POLDER/PARASOL polarization data based on a self-defined aerosol model

The characterization of surface reflection and the selection of an appropriate aerosol model are key problems in aerosol retrieval over land. Due to the amount of polarized light reflected by ground targets is small, the selection of an aerosol model is the main problem in aerosol retrieval based on polarization data. In this study, a self-defined aerosol model is proposed to retrieve aerosol optical depth (AOD) from 2008 to 2009 in the Yangtze River Delta from Polarization and Directionality of the Earth's Reflectance (POLDER) and Polarization and Anisotropy of Reflectance for Atmospheric Sciences coupled with Observation from a Lidar (PARASOL) data. The model was established using the volume percentages of aerosol components retrieved by Aerosol Robotic Network (AERONET) ground-based measurements. The results show that the volume percentages of aerosol components in the study area are 0.31, 0.55, 0.01 and 0.13 for dust, water-soluble, oceanic and soot particles, respectively, which are quite different from those of the continental model defined in the standard radiation atmosphere (SRA) aerosol models. The accuracy of AOD retrieved by the self-defined aerosol model (r = 0.75, RMSE = 0.20) is higher than that by the continental model (r = 0.41, RMSE = 0.39). Therefore, selecting a more suitable aerosol model can significantly improve the retrieval precision of AOD.