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

Satellite-derived broad-band albedo offers a useful tool for monitorin g surface conditions. Given the limited wavelength window of most sate llite radiometers, satellite albedo studies need to define narrow-band to a broad-band transformations. Signals from the AVHRR channels on b oard the NOAA-11 satellite, the Meteosat visible channel and a rectang ular 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 i n Tanre: er al. (1990) was used to obtain top of the atmosphere radian ces. The derived signals were then correlated to predict broadband alb edo and the Meteosat response via the two AVHRR signals. The results i ndicated that the use of the two AVHRR bands makes the narrow-band to broad-band conversion independent of the surface type. Finally, the re gression was applied to two concurrent AVHRR and Meteosat images so as to compare a broad-band AVHRR-derived top of the atmosphere (TOA) alb edo for the Meteosat-band with a corresponding TOA albedo from Meteosa t data. The results of the comparison illustrated the anisotropic char acter of surface reflection.