Calibration Comparisons between Seviri, Modis, and Goes Data

Remote sensing of cloud and surface properties from different satellites requires consistent calibration of the instruments on each satellite. The unique spectral, spatial, and temporal resolutions of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on the new Meteosat Second Generation, Meteosat-8, give it the potential for providing unprecedented scientific data, especially when combined with other satellites. In this study, five of the SEVIRI channels are intercalibrated with similar channels on other satellites to facilitate synergistic analyses and tuning of algorithms for remote sensing of surface and atmospheric components. The MODerate resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua satellites and the twelfth Geostationary Operational Environmental Satellite (GOES) imager have spectral channels similar to those on SEVIRI. A matched-ray technique combines pairs of pixel sets from each satellite at almost the same times from nearly the same angles. The gain for the 0.65-μm channel on Meteosat-8 appears to have increased since launch. All three comparisons indicate that the gain is nearly 7% greater than the nominal value. The 0.81-μm channel gain appears to have increased by 16% as of April 2004. The 1.6-μm channel calibration differs by only 3% from the corresponding Terra MODIS gain. The 3.89-μm channel yields brightness temperatures that are 6-7 K too small on average compared to MODIS and GOES-12 data at temperatures above 280 K. The large bias is apparently due to a spectral leak in the channel-4 filter. The infrared channel (10.75 μm) appears to be too warm by ~1 K compared to the other three sensors. Examination of the intercalibration results will continue with studies of the spectral differences, potential errors in the other instrument calibrations, and assessment of the calibrations in other SEVIRI channels.