An evaluation of the performance of IMERG hourly precipitation estimates in a geographical sub-region with complex terrain and climate conditions: a case study in the upper Red River Basin

This study comprehensively evaluates four satellite precipitation estimates (SPE) of the version 6 (V06) of Integrated Multi-satellite Retrievals for Global Precipitation Measurement Mission (IMERG) at hourly scale in the upper Red River Basin (URRB), located in Yunnan, by applying 12 rain gauges during the rainy season (May to October) from 2019 to 2020. Four SPE includes IMERG-E, IMERG-L, IMERG-FU and IMERG-FC, with IMERG-FC is calibrated by the Global Precipitation Climatology Centre (GPCC) gauge. Due to the complex terrain of the URRB, we divide the URRB into three subregions. The evaluation considers precipitation detection capability (POD, FAR and CSI), correlation (CC), error situation (RMSE and RBIAS) and the quantitative analysis index (CPI). The results show that (1) among these SPE, IMERG-FC always has higher POD and FAR, better correlation and larger RBIAS. (2) In the URRB, the results produced by all SPE are overestimates compared to ground-based observations (GBO). And, the detection capability of IMERG is better in the low precipitation threshold but worsens with the increasing precipitation thresholds. (3) IMERG shows worse performance in the dry-hot valley than in the other two areas. (4) The performance of IMERG-L is better than IMERG-FC and other SPE in the URRB.