Dependence of GPM IMERG products on precipitation intensity in Catalonia.

Satellite precipitation estimates (SPE) offer an excellent way to complement information on the spatio-temporal distribution of precipitation in semi-arid regions, such as Catalonia (NE Spain). The network of automatic weather stations of the Meteorological Service of Catalonia is used to evaluate the performance of the Integrated Multisatellite Estimates for GPM (IMERG). The semi-hourly scale analysis considered five categories related to precipitation intensity (light, moderate, heavy, very heavy, and torrential) and an analysis of two case studies of extreme precipitation was performed. Results found indicate that IMERG tends to overestimate light precipitation, while showing underestimates (errors above 60%) of cumulative precipitation in the rest of the intensity thresholds. This behaviour is related to the variability of precipitation on a point scale provided by the rain gauges and the uncertainties generated in the meshing process of the IMERG products. For high precipitation intensities, a time lag appears between satellite estimates and observations, related to the fact that the estimated precipitation may transform differently from the actual cloud movement. In addition, errors may be directly associated with the lack of information from the passive microwave (PMW) sensor. Finally, it is concluded that while IMERG can capture the spatio-temporal variability of the region in general, it has significant shortcomings in the detection of extreme sub-daily precipitation events. This research has been funded by projects WISE-PreP (RTI2018-098693-B-C32) and ARTEMIS (PID2021-124253OB-I00) and the Institute for Water Research (IdRA) of the University of Barcelona.