Distribution of the brightness temperature of land surfaces determined from AVHRR data

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Abstract
The surface temperature of the Earth is a very important climate parameter. With remote sensing techniques its global distribution can be derived with good temporal and spatial resolution. The 10·7 μm and ll·9 μm channels of the Advanced Very High Resolution Radiometer (AVHRR) aboard the NOAA satellites provide information for monitoring the surface temperature. In principle, the sea surface temperature (SST) can be obtained twice a day with the split window algorithm. An algorithm has been developed to determine the brightness temperature of arbitrary surfaces from the data of one AVHRR channel. It takes into account the dominant effects as scan angle dependency, surface heating and different atmospheric conditions. Neglecting one of these effects causes errors that are bigger than those due to unknown emissivity of natural surfaces of the Earth, Atmospheric parameters are taken from actual radiosonde data. Land surface temperatures can be determined at least four times a day, in high latitude regions even more often, with an accuracy of about l·6 deg K.