THE ATMOSPHERIC CORRECTION FOR SATELLITE INFRARED RADIOMETER DATA IN POLAR-REGIONS

Mie scattering models suggest that the thermal infrared emissivity of snow is relatively insensitive to variations in its properties and is dependent, primarily, on viewing angle. This gives rise to the possibi lity of accurately measuring snow surface temperatures, over the polar ice sheets, using satellite infrared radiometers operating in the win dow region at 10-13 microns. These instruments were designed, primaril y, to measure sea surface temperature and a substantial body of work h as been undertaken on correcting for the effects of variable absorptio n by the atmosphere over oceans. The atmospheric conditions over the A ntarctic and Greenland ice sheets are significantly different, however , and require special treatment. A three year dataset of radiosonde me asurements, collected from six Antarctic stations, is used to investig ate the behaviour of the ''split-window'' algorithm. The same dataset has been used to test the performance of a dual-view algorithm that ca n be used with the Along Track Scanning Radiometer onboard ERS-1. It i s shown that, given accurate emissivity estimates, the atmospheric cor rection has an rms error of 0.015 K using the dual-view method. Combin ed with the excellent calibration and stability of the Along Track Sca nning Radiometer and pixel averaging to reduce the detector noise it i s possible to derive snow surface ''skin'' temperatures to an accuracy of about 0.1 K.