The surface albedo quantifies the fraction of the sunlight reflected by the surface of the Earth. Following the definition of the black-sky albedo as an Essential Climate Variable by GCOS we offer this type of albedo as retrieved from SPOT data here. The black-sky albedo or directional albedo or directional-hemispherical reflectance is the integration of the bi-directional reflectance over the viewing hemisphere. It assumes all energy is coming from a direct radiation from the sun, it is computed for a specific time.
Daily top-of-canopy reflectances are normalized of a 30-day long synthesis period by inversion of a semi-empirical linear kernel-driven reflectance model; the used weighting function favours the most recent daily observations of the compositing 30-day period. Spectral directional and hemispherical albedos are estimated using the spectral coefficients resulting from the model inversion and the angular integral of kernel functions pre-computed and stored in look-up-tables. Finally broadband albedos are calculated by linear relationship with spectral albedos over visible ([0.4µm-0.7µm]), near-infrared ([0.7µm-4µm]), and total shortwave ([0.3µm-4µm]) bands, weighted by the spectral irradiance.
For more information we refer to the ATBD mentioned in the references section.
This is version 1 of this data set provided by COPERNICUS Global Land Service, downloaded from the data server at VITO in October 2015.
Data were downloaded in hdf5 file format with 1/112° grid cell resolution, organized in tiles of 10° latitude x 10° longitude. Data were block-averaged onto a 0.5° x 0.5° plate carree grid. Data are available for the latitude range 60°S to 80°N. Note, however, that limited solar illumination reduces the maximum northern latitude to smaller values during winter.
This data set has been put into our data base on Dec. 3, 2015.