Evaluation of the integrated multi-satellite retrievals for global precipitation measurement over the Tibetan Plateau

Abstract

The availability of high-resolution satellite precipitation measurement products provides an opportunity to monitor precipitation over large and complex terrain and thus accurately evaluate the climatic, hydrological and ecological conditions in those regions. The Global Precipitation Measurement (GPM) mission is an important new program designed for global satellite precipitation estimation, but little information has been reported on the applicability of the GPM’s products for the Tibetan Plateau (TP). The object of this study is to evaluate the accuracy of the Integrated Multi-Satellite Retrievals for GPM (IMERG) Final Run product under different terrain and climate conditions over the TP by using 78 ground gauges from April 2014 to December 2017. The results showed the following: (1) the 3-year average daily precipitation estimation in the IMERG agrees well with the rain gauge observations (R2=0.58, P<0.01), and IMERG also has a considerable ability to detect precipitation, as indicated by a high probability of detection (78%–98%) and critical success index (65%–85%); (2) IMERG performed better at altitudes from 3000 m to 4000 m with a small relative bias (RB) of 6.4%. Precipitation change was not significantly affected by local relief; (3) the climate system of the TP was divided into four climate groups with a total of 12 climate types based on the Koppen climate classification system, and IMERG performed well in all climate types with the exception of the arid-desert-cold climate (Bwk) type. Furthermore, although IMERG showed the potential to detect snowfall, it still exhibits deficiencies in identifying light and moderate snow. These results indicate that IMERG could provide more accurate precipitation data if its retrieval algorithm was improved for complex terrain and arid regions.