Evaluation of the Performance of Multi-Source Satellite Products in Simulating Precipitation over the Tensift Basin in Morocco

The Tensift basin in Morocco is prominent for its ecological and hydrological diversity. This diversity is marked by rivers flowing into areas such as Ourika. In addition to agriculture, the basin is a hub of variable land use systems. It is important to have a better understanding of the relationship between simulated and observed precipitation measurements in this region to be able to better understand the role of precipitation in the variability of the climate and water resources in the basin. This study aims at evaluating the performance of multi-source satellite products against weather stations precipitation in the basin. In this work, the satellite product based data were first culled for seven satellite products namely PERSIANN, PERSIANN CDR, TRMM3B42, ARC2, RFE2, CHIRPS, and ERA5 (simulated precipitation) from, CHRS iRain, RainSphere, NASA, EUMETSAT, NOAA, FEWS NET, ECMWF respectively. Precipitation observations data from six weather stations, located at Tachedert (2343 m), Imskerbour (1404 m), Asni (1170 m), Grawa (550 m), Agdal (489 m), and Agafay (487 m) at different altitudes, latitudes and temporal scales (1D, 1M, 1Y), over the period 13/05/2007 and 31/09/2019, at Tensift basin were used. The data were compared and analyzed through inferential statistics such as Nash-Sutcliffe Efficiency Coefficient, Bias, Root Mean Square Error (RMSE), Root Mean Square Deviation (RMSD), the standard deviation, the Correlation Coefficient (R) and the Coefficient of Determination (R²) and visualized through taylor diagrams and scatter plots to have a visual idea of the closeness between the seven satellite products and the observed precipitation data. A second analysis was carried out on the monthly precipitation resulting from the six weather stations based on standardized precipitation index (SPI) in order to  determine the onset, duration, and magnitude of the meteorological drought. The results show that PERSIANN CDR performs best and is more reliable with regrad to its ability to estimate precipitation rates over a wide spatial and temporal scale over the basin. The precipitation of Persiann CDR  has significant rates for the different statistics (Bias: -0.05 (Daily asni), RMSE: 2.86 (Daily Agdal), R: 0.83, R²:0.687 (Monthly Agdal)). However, most of the time, this product records low or negative Nash values (-6.06 (Annual Grawa)), due to the insufficient weather station data in the study area (Tensift). It  was observed that TRMM overestimates precipitation during heavy precipitation and underestimates during low precipitation. This makes it important for the latter observations to be viewed with caution due to the quality of annual comparison results and underscores the need to develop more efficient precipitation comparison approaches. Also, the performance of the satellite products is better at low altitudes and during wet years. Finally, it was concluded from the SPI that Tensift Region has experienced 13 drought periods over the study period, with the longest event of 12 months was from Marsh 2015 to February 2016 and  the most intense event with the highest drought severity (19.6) and the lowest SPI value (-2.66) was in 2019.