Albedos and angle-corrected NDVI for the Brazilian LBA study area from AVHRR multiangle reflectance inversions

This study investigates the application of a model of the surface bidirectional reflectance distribution function (BRDF) in deriving surface spectral albedo and in correcting angular effects in remotely sensed images at the regional and global scales. The authors apply the Ambrals BRDF model to a 30-day multiangular data set of daily AVHRR GAC images taken over South America in July, 1987 and produce images of surface spectral albedo in the visible and near-infrared bands and the angle-corrected normalized difference vegetation index (NDVI). Comparison between these images and surface information provided for the area where the future LBA (The Large Scale Biosphere-Atmosphere Experiment in Amazonia) field experiment will occur indicates that albedo and NDVI calculated by the Ambrals BRDF model are in better agreement with the independent surface characterizations than those derived from conventional approaches, which do not consider effects of surface reflectance anisotropy.