Determination of the clear-sky planetary albedo from AVHRR using a bi-directional reflectance model

Abstract

Clear-sky planetary albedos are derived from NOAA-9 AVHRR data during 1986 over the U.S. Great Plains with several distinct surface types (shrubland, grassland, deciduous and coniferous forests). The cloud-free observations are selected using a combination of absolute threshold and spatial coherence cloud-screening procedures. The broadband albedo is approximated from the narrow-band visible and near-infrared albedos. Bi-directional reflectivity models are applied to account for the effect of Sun-target-sensor geometry. The corrected albedos are converted to daily means using a directional model to account for the dependence upon sun angle. The results indicate a significant reduction in variability of the observed albedos. The efficiency of the model application is demonstrated on two examples: 1) using time series of cloud-free observations over one target and 2) using one daily image of mapped data in July, 1986.