Evaluation and Comparison of Rainfall Data for Semi-Arid Bayech Basin with GPM IMERG/TRMM 3B42 Rainfall Products.

The performance of the Tropical Precipitation Measurement Mission (TRMM) and its successor, Global Precipitation Measurement (GPM), has provided hydrologists with a source of critical precipitation data for hydrological applications in basins where ground-based observations of precipitation are sparse, or spatially undistributed. However, as their performance varies from region to region, it is of interest to evaluate the accuracy of satellite-derived rainfall products at the basin scale using rainfall observations. In this study, we evaluated and demonstrated the performance of the GPM and TRMM rainfall datasets against the rainfall observations over the Bayech basin. We performed the analysis on a monthly time scale from 2001 to 2019, using multiple statistical evaluation criteria and graphical methods. While both GPM-IMERG and TRMM showed good agreement with ground-observed rainfall data at a monthly time scale. Furthermore, the modeling results illustrate that both satellite precipitation products tend to underestimate precipitation during wet seasons and overestimate them during dry seasons, while they have a better spatial distribution of precipitation measurements performance, which shows the importance of their use for basin modeling and potentially for flood forecasting in dryland catchment areas. The study thus concluded that TRMM or GPM-IMERG rainfall data can be used as a surrogate in the absence of ground-based observed rainfall data for monthly agro-hydrological studies. KEYWORDS: Rainfall, TRMM, GPM, modeling, Tunisi