Patterns and Teleconnection Mechanisms of Extreme Precipitation in Ethiopia during 1990–2020

Abstract

The occurrence of extreme precipitation events always leads to a mass of disasters. In this study, based on daily precipitation data from 20 meteorological stations in Ethiopia, we performed a detailed analysis of patterns and trends of ten extreme precipitation indices during 1990–2020. Our study revealed that different topographic conditions on the Ethiopian Plateau, Ethiopian savanna and Ethiopian desert resulted in great differences in patterns and trends of extreme precipitation. Notably, extreme precipitation intensity indices (Rx1day, Rx5day, SDII) and amount indices (R95pTOT) showed significant downward trends in the eastern desert (averagely −1.0 mm/year, −3.0 mm/year, −0.25 mm day−1/year, −6.0 mm/year) and upward trends in the northern plateau and southern savanna (averagely 0.3 mm/year, 0.4 mm/year, 0.05 mm day−1/year, 3.0 mm/year). These implied that extreme precipitation events decreased in the eastern desert and increased in the northern plateau and southern savanna during the past thirty years. Annual trends of the CDD index were upward (0.5 to 1.9 days/year) in most of Ethiopia while those of the CWD index were close to zero in most of Ethiopia, indicating that Ethiopia faced a longer duration of drought in the past thirty years. Moreover, we revealed that the local mean temperature, local mean precipitation, Southwest Asian summer monsoon and West African summer monsoon have significant impacts on the intensity, amount and duration of extreme precipitations in Ethiopia.