Spatial Resolution Enhancement of SSM/I Microwave Brightness Temperatures and Its Impact on Rainfall Retrieval Algorithms
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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In this study the impact of spatial resolution enhancement is tested on estimates of typhoon rainfall using microwave measurements from the Special Sensor MicrowaveImager SSMI. Passive microwave estimates of rainfall are susceptible to errors from non-complete beam filling. The SSMI ground footprints for the 19, 22, and 37 GHz channels have considerable overlap and thus deconvolution techniques can be applied to enhance spatial resolution. A backus-Gilbert matrix transform approach is utilized to accomplish the deconvolution so as to minimize noise amplification as suggested by Stogryn 1978. Various validation procedures are performed to demonstrate the effectiveness of the method. The deconvolution scheme is evaluated in terms of its impact on integrated rainfall throughout the life cycle of a number of tropical storms which occurred during the 1987 hurricane and typhoon season. This evaluation was performed for a single frequency emission algorithm, a single frequency scattering algorithm, and three multiple frequency algorithms, each with different properties and scientific approaches. While rainfall patterns detected by all algorithms were qualitatively enhanced, quantitative responses were different for each algorithm.