The validation of ATSR using aircraft radiometer data over the tropical Atlantic

Abstract

An airborne infrared radiometer with channels at 11 and 12μm spectrally matched to those on the ATSR was used to make nadir, 60° to nadir, and zenith view radiance measurements at a number of different altitudes from 70m to 8km above the sea surface. ATSR retrievals of SST (using both nadir and forward views) were compared with SSTs inferred from low-level radiance measurements of the sea surface that were unaffected by atmospheric absorption. ATSR SSTs retrieved using the nadir only views had negative (ie, cold) biases of about 2K. If the forward view was also included in the retrieval, the negative biases reduced to approximately 0.7K. Radiance profiles through the atmosphere were also obtained for comparison with those computed by the Rutherford Appleton Laboratory radiative transfer model, which had been used to generate the ATSR SST retrieval coefficients. These showed that a positive (warm) bias of 1.5K exists between the model and nadir view aircraft radiometer meaurements at the 6km altitude for these tropical atmospheres. -from Authors