NARROW-BAND TO BROAD-BAND CONVERSION FOR METEOSAT-VISIBLE CHANNEL AND BROAD-BAND ALBEDO USING BOTH AVHRR-1 AND AVHRR-2 CHANNELS

Satellite-derived broad-band albedo offers a useful tool for monitoring surface conditions. Given the limited wavelength window of most satellite radiometers, satellite albedo studies need to define narrow-band to a broad-band transformations. Signals from the AVHRR channels on board the NOAA-11 satellite, the Meteosat visible channel and a rectangular spectral band from 0.3 to 2.5 mu m were simulated for a set of 20 representative land surfaces. The radiative transfer code described in Tanre: er al. (1990) was used to obtain top of the atmosphere radiances. The derived signals were then correlated to predict broadband albedo and the Meteosat response via the two AVHRR signals. The results indicated that the use of the two AVHRR bands makes the narrow-band to broad-band conversion independent of the surface type. Finally, the regression was applied to two concurrent AVHRR and Meteosat images so as to compare a broad-band AVHRR-derived top of the atmosphere (TOA) albedo for the Meteosat-band with a corresponding TOA albedo from Meteosat data. The results of the comparison illustrated the anisotropic character of surface reflection.