A Simple Method for Estimating Monthly Mean Albedo of Land Surfaces From AVHRR Data

Abstract

It is suggested that the observed periodicity of cloud-free, visible and near-infrared data from the Advanced Very High Resolution Radiometer (AVHRR) onboard NOAA-9 for a particular target can be efficiently used for deriving the monthly mean clear-sky planetary albedo. The broadband albedo is approximated by a linear combination of visible and near-infrared albedos. The new method of 9-day compositing distributes the clear-sky observations over the sun-target-sensor geometry combinations and weights them by the occurrence of each combination during a particular month. It is shown that the monthly mean clear-sky planetary albedo can be estimated solely from the visible and near-infrared data in a model-independent manner. The surface albedo is then obtained by applying a simple atmospheric correction to the derived clear-sky planetary albedo. A comparison of the results of the present method and those obtained by using the “minimum albedo” method indicates that the latter may lead to an underestimation of monthly values because of the angular variation in clear-sky observed albedos. The derived surface albedos are compared with those reported in climatological studies based on ground observations.