Evaluation of IMERG V07B precipitation estimates on gauge-observed extreme-rainfall days in a karst region of Guangxi, China

Karst areas experiencing rocky desertification have low precipitation storage capability and are highly vulnerable to floods during severe rainstorm (SR) events (daily rainfall ≥ 100 mm in China). The performance of Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG) under these conditions therefore requires detailed evaluation. In this study, IMERG V07B products are evaluated during SR events using ground observations from 53 rain gauges in the karst rocky desertification areas of Guangxi, China, from 2000 to 2024. The main results are as follows: (1) Temporally, SR events are concentrated from May to July, with the highest incidence during 2015–2019. Spatially, SR frequency increases from west to east, with high-value centers clustered in northeastern Guangxi. (2) All three IMERG V07B products systematically underestimate SR events over the karst rocky desertification areas, with retrieval errors showing an east–west spatial gradient. (3) Among the best-performing products in terms of RB and RMSE, IMERG-L shows better RB performance than IMERG-E and IMERG-F in most months with observed SR events from 2000 to 2024.