Stochastic Prediction of Kirmt (June - September) Rainfall over North Central Ethiopian Highlands

Summer (June - September) rainfall over the highlands of the Nile River basin, mainly over the Ethiopian highlands, is the major water resource of Ethiopia, Sudan and Egypt. Thus, studies on identifying and modeling of the causes for years to years variation of the rainfall over Ethiopian highlands are very important.

In this paper the stochastic link between the summer rainfall totals of the north-central Ethiopian highlands with sea-surface temperatures, SOI, and sunspot numbers covering the period from 1900-1990 is established. For this purpose a transfer function pulse noise model is used. The inputs are: the April-June sea-surface temperature anomalies of the south Atlantic, the south Indian and the tropical east Pacific Oceans, and the June SOI here represented by the June Darwin sea level pressure, and the annual sunspot numbers. The output is the June-September rainfall total of the north-central Ethiopia highlands. These input variables are selected because they are significantly correlated with the summer rains over the north-central Ethiopian highlands. Moreover, the Atlantic and the Indian Oceans are the major sources of moisture for the region.

The result shows that the constructed stochastic transfer function plus noise model explains 70% of the June-September rainfall variability in the period 1900-1990.

The model can be used to provide a forecast for a summer rainfall amount over the north-central Ethiopian highlands. This forecast information can be of high practical value particularly for rained agricultural community in mountainous areas.