Evaluation of the hydrological utility of the GPM IMERG satellite precipitation products

Satellite precipitation products (SPPs) provide valuable information for hydrological modelling. This paper presents an evaluation of the hydrological utility of in total six Integrated Multi-satellitE Retrievals for GPM (IMERG) products. Specifically, as to the IMERG V06 and V07, both the near-real-time products, i.e., Early and Late, and the post-real-time product, i.e., Final, are evaluated at the daily timescale. Based on the GR4J hydrological model, three numerical experiments respectively focusing on the accuracy of precipitation estimation, the usefulness in streamflow simulation and the effectiveness in flood simulation are devised. Through a case study of 20 catchments across 5 climate zones in Australia from 2000 to 2021, the results highlight that the IMERG V07 products generally outperform the IMERG V06 products in the hydrological utility. For the accuracy of precipitation estimation, the relative bias (rBias) at the point scale of the IMERG V07 products tends to be lower than that of the IMERG V06 products. The median rBias is respectively −31.17% and −16.61% for the IMERG V06 and V07 Early products, is respectively −29.11% and −12.77% for the IMERG V06 and V07 Late products and is respectively −7.83% and −7.46% for the IMERG V06 and V07 Final products. There are evident improvements in streamflow simulation from the IMERG V06 products to the IMERG V07 products, with the median Kling-Gupta efficiency (KGE) increasing from 0.32 to 0.40 under the Early products, from 0.33 to 0.41 under the Late products and from 0.59 to 0.61 under the Final products. Regarding flood simulation, the percent bias in the flow duration curve high-segment volume (FHV) is reduced from the IMERG V06 products to the IMERG V07 products, with the median FHV increasing from −61.52% to −39.29% for the Early products, from −59.28% to −35.18% for the Late products and from −38.85% to −30.64% for the Final products. Taken together, the evaluation of hydrological utility facilitates valuable insights into the applications of the IMERG products to precipitation monitoring, hydrological modelling and flood forecasting.