Retrieval of Surface Reflectance and Aerosol Optical Thickness Simultaneously from Space Measurement over Land: Basic Theory and Simulation
利用云下阴影实现陆地上空气溶胶和地表反射率的同时反演—理论方法和模拟

The satellite measurements in the visible and near Infrared band are the contribution of surface reflectance and atmospheric back scattering, and it is very difficult to distinguish one form the other for both contribution have the same order over land. The images from high spatial resolution orbit sensor such as TM5 flying on LANDSAT are very clear to discriminate cloud and the shadow since they are projected on the surface from cloud free pixels in the visible hand. Over a nontransparent cloud shadow, the radiance obtained from satellite measurement is the contribution of atmospheric path radiance and surface diffuse reflection; while, over a bright area surrounding the cloud shadow, besides the contribution of atmospheric radiance and surface diffuse reflection, the surface direct reflection also contributes to the radiance measured from satellite. Based on this theory, the difference between the two radiances and its relationship with the surface reflectance and aerosol optical thickness are analyzed, and a new method to retrieve surface reflectance and serosol optical thickness simultaneously over land is developed. At the end of this paper, sensitivity analysis of measurement, single scattering albedo and aerosol scattering phase function to the retrieval of surface reflectance and aerosol optical thickness are given.