Recent changes in rainfall and rainy days in Ethiopia

Abstract Changes in annual, June–September and March–May rainfall and rainy days herein (defined as a day with rainfall greater than 1 mm) have been analysed based on 11 key stations located in different climatic zones of Ethiopia over the common period 1965–2002. The progressive Mann–Kendall trend test shows that there is no trend in the annual rainfall total, the seasonal rainfall total or rainy days over central, northern and northwestern Ethiopia in the period 1965–2002. In contrast, the annual and the June–September total rainfalls for the eastern (Jijiga, 137 mm/decade), southern (Negele, 119 mm/decade) and southwestern (Gore 257 mm/decade) stations show a significant decline since about 1982. Correlation analysis shows that the decline of rainfall in eastern, south and southwestern Ethiopia is caused by the corresponding persistent warming of the South Atlantic Ocean over the period approximately from 1986 to 2002. The sea‐surface temperature (SST) over the tropical eastern Pacific Ocean is not significantly correlated with the main rainfall of the semi‐arid lowland areas of eastern, southern, and southwestern Ethiopia, except at marginal zones in transition to the Ethiopian Highlands. June–September rainfall over the Ethiopian Highlands is positively correlated to the equatorial east Pacific sea‐level pressure and the southern oscillation index, and negatively correlated to SST over the tropical eastern Pacific Ocean as expected, confirming again that warm El Niño–southern oscillation episodes are associated with below‐average June–September rainfall over the Ethiopian Highlands. Copyright © 2004 Royal Meteorological Society