贵州地区CMORPH卫星降水产品的误差订正

CMORPH卫星反演降水产品具有全天候、全球覆盖的特点,其时空分布相对均匀、独立,但是CMORPH本质上是通过间接手段反演得到,其降水精度无法与地面观测降水精度相比,并且存在一定的系统误差.结合地面自动站降水资料采用概率密度匹配法对贵州地区CMORPH卫星反演降水产品进行系统误差订正,该方法将每个格点的卫星降水累积概率...

BIAS CORRECTION OF CMROPH SATELLITE PRECIPITATION PRODUCTS OVER GUIZHOU

The CMORPH satellite-retrieved precipitation products feature all-weather and global coverage, and their spatio-temporal distribution is relatively uniform and independent. However, CMORPH products are obtained using indirect methods, their accuracy is lower than that of ground observations, and there is systematic bias. Using the precipitation data from ground automatic stations, this paper adopts the probability density matching method to correct the system bias of the CMORPH satellite precipitation products over Guizhou. The satellite precipitation cumulative probability distribution curve of each grid point is matched with the surface precipitation probability density distribution curve to correct precipitation bias, and the process is influenced by the precipitation cumulative probability distribution fitting curve. Given that the precipitation cumulative probability distribution is non-normal, Gamma distribution is selected to fit the precipitation cumulative probability distribution curve. Through the analysis of the correction results of three precipitation processes in May 2018, following conclusions are obtained: (1) There is obvious and non-independent systematic bias in the hourly CMORPH satellite-retrieved precipitation products. The bias varies with the level of precipitation, and sometimes precipitation is overestimated. (2) On the hourly scale, the cumulative probability density of surface precipitation shows an exponential decay distribution, while the cumulative probability density distribution of CMORPH products is more complicated, and the probability of precipitation in the interval of moderate rain and heavy rain is higher. (3) The CMORPH products corrected by using the probability density matching method are closer to ground precipitation than those before the correction. The magnitude and range of heavy precipitation center are significantly reduced, and the average absolute error and root mean square error are reduced. The deviation correction value is between 0.114~0.468 mm/h, and the root means square error is between 0.24~1.49 mm/h. The accuracy of the CMORPH satellite precipitation products after correction by using the probability density matching method has been significantly improved and is closer to actual precipitation.