Development of satellite precipitation maps for hydrologicalapplications

为了进一步完善GSMaP等卫星降水图，我们在本项目中进行了两项研究。首先，对新标准产品TRMM/PR （Version 7, V7）中的雨率估算值进行了评估。由于地面参考技术的改进，在V7中出现的强降雨估计比以前的版本更频繁。我们还利用日本地区的高时间分辨率雨量计数据对V7的雨率估计进行了评估，并得出结论：强降雨估计（高于50 mm/h）被高估了，但其偏差小于50%。其次，提出了一种微波辐射计两次测量间隔的降雨探测新方法。在该方法中，我们从低频通道的亮度温度下降来判断下雨或无雨。在植被较少的地区，该方法与GSMaP中使用的方法具有可比性。

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.