Evaluation of the Envisat-aatsr Land Surface Temperature Algorithm with Ground Measurements in the Valencia Test Site

RESUME In this work we describe the validation of the land surface temperature (LST) product derived from the Advanced Along-Track Scanning Radiometer (AATSR). A test site was established in a large, flat and homogeneous area of rice crops close to Valencia, Spain. Coincidentally to the Envisat morning overpasses, radiometric temperatures were measured along transects covering the area of one AATSR pixel (1 km) during the summers of 2002-04. Four thermal radiometers were used, which were calibrated and intercompared through the campaigns. Radiometric temperatures were corrected for emissivity effects using field emissivity and downwelling sky radiance measurements. Coincident AATSR data (L1b and LST product) are currently available for five days in 2002. For these scenes, a comparison was made between the ground measurements and the collocated AATSR LST product and other split-window algorithms as well. Results show a good agreement between groundmeasured and satellite derived LSTs, with maximum differences of ±1 oC, and standard deviation of ±0.8 oC.