Retrieval of land surface albedo from satellite observations: A simulationstudy

Land surface albedo is a critical parameter affecting the earth's climate a nd is required by global and regional climatic modeling and surface energy balance monitoring. Surface albedo retrieved from satellite observations at one atmospheric condition may not be suitable for application to other-atm ospheric conditions. In this paper the authors separate the apparent surfac e albedo from the inherent surface albedo, which is independent of atmosphe ric conditions, based on extensive radiative transfer simulations under a v ariety of atmospheric conditions. The results show that spectral inherent a lbedos are different from spectral apparent albedos in many cases. Total sh ortwave apparent albedos under both clear and cloudy conditions are-also si gnificantly different from their inherent total shortwave albedos. The conversion coefficients of the surface inherent narrowband albedos deri ved. from the MODIS (Moderate Resolution Imaging Spectroradiometer) and the MISR (Multiangle Imaging Spectroradiometer) instruments to the surface bro adband inherent albedo are reported. A new approach of predicting broadband surface inherent albedos from MODIS or MISR top of atmosphere (TOA) narrow band albedos using a neural network is proposed. The simulations show that surface total shortwave and near-infrared inherent albedos can be predicted accurately from TOA narrowband albedos without atmospheric information,, w hereas visible inherent albedo cannot.