Development of satellite precipitation maps for hydrologicalapplications

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For further improvement of satellite precipitation maps such as GSMaP, we have conducted two studies in this project. Firstly, rain rate estimates in the new standard product of TRMM/PR (Version 7, V7) were evaluated. Owing to the improvement of surface reference technique, heavy rainfall estimates appear more frequently in V7 than in the previous version. We also evaluated V7’s rain rate estimates with high-temporal resolution rain gauge dataset over Japan and concluded that the heavy rainfall estimates (higher than 50 mm/h) are overestimated, but their biases are less than 50%. Secondly, we developed a new method to detect rainfall for the interval of two measurements of microwave radiometers. In this method, we judge rain or no-rain from the decrease in brightness temperature at low frequency channels. This method yields comparable results with the method used in GSMaP for less vegetated area.