Aerosol Optical Thickness retrieval over snow-covered surface using AATSR data

Aerosol Optical Thickness (AOT) retrieval over very bright surface is a great challenge because the surface contribution dominates the Top Of Atmosphere (TOA) signal. In this paper, we presented a method for AOT retrieval over snow-covered surface. For the first step, the surface is assumed to be a mixture between snow and ice. The main idea is that the ratio between nadir and forward observation was used for AOT retrieval. For different snow-covered surface type, the surface reflectance is estimated by a mixing model of snow and the other item (ice), tuned by the normalized Differential Snow Index (NDSI) of the satellite observation. Then the AOT can be obtained using Look-Up-Table (LUT) method. In the paper, we mainly focus on the Arctic region, which is a very nice study area for mixture between snow and ice. Validation between ground-based measurements and satellite-derived results shows good agreement. Thus the method provides a promising method for global-covered and whole season AOT retrieval. In the next step, three different regions will be used for validation of the method, for the Arctic region, Canada, Beijing, was chosen for pure snow-ice mixture, snow-vegetation mixture and snow-solid mixture surface.