Using a geographic information system to improve Special Sensor Microwave Imager precipitation estimates over the Tibetan Plateau

Abstract

1 This study examines the potential of spatial modeling using geographic information systems (GIS) to improve the precipitation estimates based on Special Sensor Microwave/ Imager (SSM/I) over the Tibetan Plateau. The monthly SSM/I precipitation estimates are based on the algorithm developed at the National Environmental Satellite, Data and Information Service (NESDIS) of the National Oceanic and Atmospheric Administration (NOAA). When using SSM/I estimates to predict station precipitation directly, the R-2 values ranged from 0.005 to 0.624, with a mean of 0.334 for all months. When terrain and location variables obtained from the GIS were added to the models, the R-2 values improved to range from 0.217 to 0.739 with a mean of 0.590 for all months. These variables represent effects of orographic forcing of topography, rain barrier/rain shadow, direction of moisture-bearing winds, and distance to the sources of moisture over the Tibetan Plateau. Results from this study suggest that region-specific algorithms are necessary for the SSM/I precipitation estimates over the Tibetan Plateau and that topographic analysis based on GIS can contribute significantly in improving the performance of SSM/I estimates.

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