21 December 1994 Beam-filling effect in the microwave remote sensing of precipitation
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Abstract
The passive microwave radiometers have a field of view that is much larger than the size of the raining cells, and within the rain cell the brightness temperature can reach saturation. These problems are generally referred to as the beam filling effect (BFE). We developed a technique to retrieve rain rates from the Special Sensor Microwave/Imager (SSM/I) data, which inherently incorporates the BFE. However an overestimation of rain rates was evident when the data from the Global Precipitation Climatology Project (GPCP) program became available. The procedure followed to obtain the algorithm was revised and modified, and new coefficients were calculated. This modified algorithm was tested by comparing the SSM/I derived rainfall with the corresponding values obtained by radar and rain gauges in the framework of the GPCP program. This comparison reveals two separate clusters of points, which can be related to the fact that the BFE is larger for convective precipitating clouds and smaller for stratiform clouds. An examination of the data at 19 and 85 GHz gives a clue to discriminate between these two types of rain. Then two different algorithms are proposed for the retrieval of rain from microwave data.
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Giuseppe A. Dalu, Cuddapah Prabhakara, Alberto Pompei, "Beam-filling effect in the microwave remote sensing of precipitation", Proc. SPIE 2313, Microwave Instrumentation and Satellite Photogrammetry for Remote Sensing of the Earth, (21 December 1994); doi: 10.1117/12.197343; https://doi.org/10.1117/12.197343
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