Correction of satellite precipitation data (IMERG) by considering the spatial information of rainfall in South Korea

Satellite-derived precipitation products have the advantage in terms of continuous and large observation coverages. However, satellite precipitation products often include the uncertainties that are associated with the sensors' limitations and the physical characteristics of various precipitating systems. This study presents a method to correct the difference of satellite precipitation estimates from ground-based rainfall measurements. The correction method uses an optimal number of rain gauges that is determined from the spatial variability of rainfall. That is, the spatial variability is identified by the coefficient of variation (CV) of rainfall around the satellite data and then the boundary of the gauges to be used for the correction is variably calculated by CV. The correction method is applied to the 1-hour accumulated rainfall of Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (GPM) data (IMERG: Version 05 Early run) over South Korea at the summer (June, July, August) season from 2014 to 2017. The results show that the corrected IMERG data are closer to the ground observations than the IMERG data without correction in terms of the bias and root-mean-square errors. In addition, the effect of the correction on the systematic and random error components of IMERG data is investigated. It is shown that systematic error significantly decreases after applying the correction method. The details on the improved statistics for IMERG product will be discussed.

This work was supported by Korea Environment Industry & Technology Institute(KEITI) through Water Management Research Program, funded by Korea Ministry of Environment(MOE) (127557)