The evaluation and downscaling‐calibration of <scp>IMERG</scp> precipitation products at sub‐daily scales over a metropolitan region

Abstract The Global Precipitation Measurement (GPM) Integrated Multi‐satellitE Retrievals for GPM products (i.e., IMERG) provide new‐generation satellite precipitation measurements. For urban contexts, however, the issues of its bias and insufficient resolutions still exist. This study aims to develop high‐precision high‐resolution (e.g., 0.01°/1 h) data a metropolitan region based on IMERG gauge precipitations. original product is evaluated using hourly in situ precipitations from 47 gauges. A spatial downscaling‐calibration (DC) technique then developed enhance Normalized Difference Vegetation Index. results show limited capability capture sub‐daily high‐intensity precipitation. proposed DC method significantly improves performance, with correlation coefficient (CC) increasing 0.07 0.75, probability detection improving 0.34 0.90 at scale. In terms rainfall distribution, 86% mean absolute error 80% RMSE are improved CC 0.91 average. Additionally, calibrated downscaled provides finer information local areas, capturing three times more variabilities against input data. highlight necessity observations flood risk management fine spatiotemporal resolutions.