VALIDATION OF ATSR SEA-SURFACE TEMPERATURES IN THE FAEROES REGION

Sea temperatures measured by a thermosalinograph at a mean depth of 5 m during a cruise on the RRS Charles Darwin in a region to the north-east of the Faeroe Islands were compared with high resolution (similar to 1 km) and low resolution (0.5 degree spatially averaged) Along Track Scanning Radiometer (ATSR) sea surface temperature products. In both cases the satellite measurements were, biased cooler than the in situ sea temperatures within an amount consistent with the cool skin effect and within the +/- 0.5 deg . K design specification of the ATSR. The comparison with the low resolution data gave a bias of 0.3 deg K compared with 0.4 deg K for the high resolution sea surface temperatures. In each case these biases were equivalent in magnitude to the mean estimated skin effect for the period of the comparisons. The smaller bias may result from the fact that horizontal displacement of temperature gradients during the period between satellite and in situ measurements becomes less important as the size of the averaging area is increased. Owing to cloud conditions it was necessary to relax the time window for the comparisons.