The MODIS BRDF/Albedo product: prototyping albedo retrieval using AVHRR and GOES

Abstract

Directional data acquired by both the MODerate resolution Imaging Spectroradiometer (MODIS) and the Multiangle Imaging Spectroradiometer (MISR) on NASA's Earth Observing System (EOS) will be used to produce a global bidirectional reflectance distribution function (BRDF) and albedo product once every 16 days. The product will be derived using the kernel-driven semiempirical Ambrals BRDF model, utilizing five variants of kernel functions characterizing isotropic, volume and surface scattering. The BRDF and the albedos of each land surface pixel will be modeled at a one kilometer spatial resolution in seven spectral bands spanning the visible and the near-infrared. As a prototyping activity, the authors assembled a 16-day sequence of AVHRR GAC 1-km data in red and near-infrared bands and GOES 1-km data in the visible band and applied the Ambrals model to fit BRDFs and calculate albedos for the New England region of the USA. The resulting fine-resolution albedo map shows strong spatial detail primarily related to the land covers of the region. Urban and suburban regions show BRDFs dominated by geometric-optical scattering, while multiple scattering is more important in BRDFs fitted to forested areas.