Validation of Atlantic Ocean sea surface temperatures measured by the ERS-1Along Track Scanning Radiometer

During the period from October 1991 to May 1992 the royal research ship Bransfield made its annual voyage from the United Kingdom to Antarctica and back. Whenever the measurement swath of the Along Track Scanning Radiometer (ATSR) on the ERS-1 satellite passed over the ship, the in situ skin and bulk sea surface temperatures (SSTs) were measured as well as profiles of atmospheric temperature and humidity. A total of seven cases were obtained where surface observations indicated cloud-free conditions during a satellite overpass. All the cases were in the tropical and subtropical Atlantic Ocean between 37°N and 45°S. The SSTs obtained from the ATSR nadir-view brightness temperatures were all colder than the skin SST by more than 0.5 K. The use of dual-view data made the agreement with the in situ measurements better in all but one case. In two cases agreement to better than 0.3 K could be obtained between the skin and ATSR SST when the dual-view brightness temperatures were used. In the other cases the results were poorer for a variety of reasons, including subpixel cloud contamination, anomalous atmospheric temperature and humidity profiles, and the presence of stratospheric aerosol in the Tropics following the eruption of Mount Pinatubo in June 1991. The cold bias of the ATSR SSTs is in agreement with results obtained from an aircraft-mounted infrared radiometer. This work has shown the need for regionally tuned SST algorithms rather than ones based on broad climatic zones, along with coefficients for different types of air mass within each latitude band.

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