A Long-term Global Comparison of IMERG and CFSR with Surface Precipitation Stations

As the Integrated MultisatellitE Retrievals for- Global Precipitation Measurement (GPM) (IMERG) products are expected to be available at least until mid-2030, it is highly desired that an extensive spatio-temporal comparison of IMERG be done at the in-situ level to have guidance on potential usage, especially for hydro-climatic applications in data-scarce conditions. For reference, we selected widely popular CFSR precipitation products and compared both (IMERG and CFSR) with monthly precipitation time-series accessed from in-situ global stations from National Oceanic and Atmospheric Adminstration (NOAA). This comparison was made over 2001–2020 for the extent of 5 geographical regions, 7 continents, 105 countries and ~ 50,000 surface stations using the standard metrices like NSE, VE, KGE, R, RMSE and PBIAS. IMERG has a satisfactory to a good simulation of monthly rainfall in the majority of the regions, continents, countries, and stations and outperforms Climate Forecast and System Reanalysis (CFSR). Precisely, satisfactory simulation of monthly precipitation was found for Europe (VE = 0.61), North America (0.56) and Australia (0.56) and unsatisfactory simulation was observed for other continents for CFSR. At country levels, 64 countries reveal a significantly better mean NSE with IMERG. Considering the value of automated global access to the latest precipitation data for hydrologic modelling, and the better quality of IMERG, this study also introduces a public web service: Worldwide Weather Service (W3S) for preprocessing and dissemination of IMERG precipitation for use in hydrologic modelling. The outcomes of the study are expected to guide water resources managers to use these datasets in sustainable water resources management.