Analysis of meteorological drought using satellite-based rainfall products over southern Ethiopia

Abstract. Drought is one of the recurring natural phenomena affecting the socio-economic and environmental well-being of southern Ethiopia's society. The availability of insufficient ground-based rainfall observatory networks is limiting drought-monitoring and early-warning investigations. The main objective of this study is to analyze spatial and temporal drought characteristics using high-resolution satellite-based rainfall products for the 1991–2022 period in the Southern Nations, Nationalities, and Peoples (SNNP) region of Ethiopia. The satellite-based rainfall product used in this study was selected after the evaluation of three satellite products, namely the Africa Rainfall Climatology version 2 (ARC2), the Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS), and the Tropical Applications of Meteorology using SATellite and ground-based observations (TAMSAT), against station-based rainfall for the study area space and time domains. The statistical metrics of correlation coefficient (CORR), bias (BIAS), percent bias (PBIAS), mean error (ME), mean absolute error (MAE), root mean square error (RMSE), and Nash–Sutcliffe efficiency coefficient (NSE) were used to compare and evaluate the satellite rainfall products. Accordingly, the CHIRPS shows the highest CORR of 0.96 and the highest BIAS of 1.02, which is very near to the perfect value (BIAS = 1), followed by the TAMSAT. Hence, the CHIRPS-based satellite rainfall product was used to assess the spatio-temporal patterns of meteorological drought based on the 3-month and 12-month standardized precipitation index (SPI). The results successfully grasped the known historical and recent droughts of 2022, 2021, 2015, 2014, 2010, 2009, and 2000. A high intensity and a high severity of drought were noted in the SPI-3, while the least occurrences of extreme events were recorded in the SPI-12. Additionally, severe drought situations were detected in the drought-prone areas in the southern and southeastern parts of the SNNP region. Finally, the study concludes that, to construct grid-based drought-monitoring tools for the development of early-warning systems, the CHIRPS rainfall product can be used as an additional source of information.