A comprehensive validation for GPM IMERG precipitation products to detect extremes and drought over mainland China

This study provides a comprehensive validation of Integrate Multi-SatellitE Retrievals of (IMERG) Global Pre-cipitation Measurement (GPM) products in detecting extremes and drought over mainland China. The estimated values of extreme precipitation and drought are provided by three runs (early, late and final) of the latest IMERG products (V06) and 696 in-situ gauges over mainland China during 2008-2017. The results demonstrate that the three runs of IMERG V06 exhibit a relatively good performance in detecting the spatial patterns of extreme precipitation volume. The early and late runs present limited capability to capture extreme precipitation events, while the final run performs slightly better. Based on the extreme value theory, the three runs show better performances in estimating extreme precipitation within short return period (10-yr) compared to 50-yr and 100 -yr return periods. All runs consistently underestimate extreme precipitation in all investigated return periods over eastern China. The standardized precipitation index (SPI) is used as a drought monitoring tool. The SPI of three runs of IMERG is well aligned with the in-situ data in southern and eastern China at both time and space scales, which demonstrates that the great potential of IMERG V06 in monitoring drought in these regions. However, the three runs of IMERG V06 products have inferior performances in monitoring drought over western China at four investigated timescales (1-, 3-, 6- and 12-month). This study highlights discrepancies in the capability of the IMERG products to estimate major extreme climatic variables and suggests potential avenues of research to improve the algorithm associated with the products. Meanwhile, the results of this study can benefit both developers and users of the new generation GPM IMERG products.