Calibration of METEOSAT Infrared Radiometer using Split Window Channels of NOAA AVHRR

Abstract

A multispectral/multiangular procedure is proposed to calibrate the infrared channel of METEOSAT-2 IR 1 (760?980 cm?1), using the radiances of NOAA-7 AVHRR channels 4 (870?980 cm?1) and 5 (795?885 cm?1). The METEOSAT radiance can be successfully simulated by using one or both AVHRR infrared channels. The calibration coefficients are strongly influenced by the airmass (propagation paths) or incident zenith angles (?i). With one AVHIRR channel, the best results are obtained at ?M<?N for channel 4 and at ?M>?N for channel 5. With both AVHRR channels, the best results are found at ?M = ?N; however, an overall accuracy of less than 0.2 K is achievable at almost any viewing geometry. Application of the procedure to real data shows that the calibration factor for the METEOSAT-2 IR 1 channel can be accurately estimated from the NOAA AVHRR data on the same date and zone. The method can easily be automated and used to calculate or adjust the calibration factors for METEOSAT-2.