Analysis of daily precipitation estimates for the gpm-imerg product in the sapucaí river basin, southeast region of Brazil

Abstract

Given that satellite precipitation (PP) estimates are important sources of information for hydrological models, the aim of this study is to evaluate the daily cumulative of PP from the Integrated Multisatellite Retrievals for Global Precipitation Measurement (IMERG) product from the Global Precipitation Measurement (GPM) in the Sapucaí River Basin (BHRS) which is located in southeastern Brazil. To perform this evaluation statistical performance and contingency metrics are used. The data used in the validation were the daily-accumulated PP of the rainfall stations of the National Water Agency (ANA). The period analyzed in the study comprises the summers of the years 2015 to 2019. In general, the results indicated that the IMERG underestimates the daily PP on average by 27% in the basin, with the RMSE ranging from 12.9 to 28.5 mm/day. Besides that, it was also observed that the Pearson’s correlation coefficient values in most of the analyzed grid points were below 0.7. This indicates that there is not a good correlation between the data from IMERG and the data of the rainfall stations. The contingency statistical metrics showed that the IMERG-Early Run has a low capacity to describe the rain events in the BHRS. Therefore, it can be inferred that the Early Run product from GPM-IMERG has difficulties in estimating daily PP in BHRS during the summer months.