JUNE-SEPTEMBER RAINFALL IN NORTH-EASTERN AFRICA AND ATMOSPHERIC SIGNALS OVER THE TROPICS - A ZONAL PERSPECTIVE

The connection between rainfall in northeast Africa (Djibouti, Eritrea , Ethiopia, Kenya, Somalia, Sudan, and Uganda) and various atmospheric indicators from the tropics have been investigated for the northern s ummer season. Variables used include zonal wind at 700 hPa and 200 hPa , sea-level pressure, and rainfall over other tropical areas, for the period 1951-1988. Strong significant correlations are shown with the S outhern Oscillation and the components of the Walker cell in the Pacif ic Ocean. Draughts in the Ethiopia-Uganda area are associated with El Nino events and moreover, with above normal pressure and droughts over India. Other significant relationships exist with the African monsoon . Westerly (easterly) anomalies in the lower (upper) levels are associ ated with abundant summer rainfall years in north-east Africa. These r esults are all consistent with the previously defined Walker-type circ ulations over the tropics, particularly as far as the Indo-Pacific and African cells are concerned. Although the Southern Oscillation has a dominant impact in this respect, the specific coherence of the African cell is further evidenced Preliminary findings suggest that the summe r rainfall areas of East Africa could qualify as a location for the ri sing branch of this cell.