Validation of the ATSR in Australian Waters

Abstract

The Along Track Scanning Radiometer (ATSR) was launched on the ERS-1 satellite on 17 July 1991. During the following six months, a concentrated effort was made to validate the sea surface temperature (SST) derived from data supplied by this new generation radiometer. Ship and aircraft radiometers collected “ground truth” data that were coincident with ATSR measurements and thus allowed a comparison of the surface and space measurements. A large proportion of the early validation data was obtained during four research vessel cruises in Australian waters, and a detailed analysis of those results is presented here. Ancillary data were collected to support the shipborne radiometer measurements and to allow further analyses beyond the important validation task. These data included the standard surface meteorological data, bulk SST, and, in most cases, ship-launched radiosondes. Four different algorithms derived using a theoretical atmospheric transmission model were applied to the ATSR data to provide estimates of SST, and these estimates were compared to the surface-based measurements. All the algorithms gave reasonable agreement with each other as well as agreement with the surface data. The algorithm using all six infrared measurements gave the lowest standard deviation but showed a warm bias of 0.2 K when compared to the temperature of the skin layer of the ocean. The validation results show that the ATSR instrument can provide SST within the design accuracy of 0.3 K. The results of the validation presented here are in good agreement with those reported elsewhere using other datasets. Further improvements in SST accuracy, perhaps to 0.2 K, may be expected with a more rigorous analysis of the data.