NORMALIZATION AND CALIBRATION OF GEOSTATIONARY SATELLITE RADIANCES FOR THE INTERNATIONAL SATELLITE CLOUD CLIMATOLOGY PROJECT

Procedures are described for normalizing the radiometric calibration o f image radiances obtained from the suite of geostationary weather sat ellites that contributed data to the International Satellite Cloud Cli matology Project. The key step is comparison of coincident and colloca ted measurements made by each satellite and the concurrent Advanced Ve ry High Resolution Radiometer (AVHRR) on the ''afternoon'' NOAA polar- orbiting weather satellite at the same viewing geometry. The results o f this comparison allow transfer of the AVHRR absolute calibration, wh ich has been established over the whole series, to the radiometers on the geostationary satellites. Results are given for Meteosat-2, Meteos at-3, and Meteosat-4, for GOES-5. GOES-6, and GOES-7, for GMS-2. GMS-3 , and GMS-4 and for Insat-1B. The relative stability of the calibratio ns of these radiance data is estimated to be within +/-3%; the uncerta inty of the absolute calibrations is estimated to be less than 10%. Th e remaining uncertainties are at least two times smaller than for the original radiance data.