Influences of the ENSO event on the rainfall of dry Sudan

Abstract

The paper highlights the factors affecting rainfall of the Sudan, its distribution and influences on the environment and socioeconomic conditions of the country. Four meteorological stations were selected in the dry zone in Sudan. These are: El Obeid, Khartoum, El Fashir and Kassala. The data obtained from these stations were averaged to represent the dry region. During years of prolonged (≥ 9 months) La Nina, rainfall of the region was generally above normal contrary to prolonged El Nino which is generally characterized by below normal rainfall. Furthermore, higher forecast capabilities were associated with the La Nina stage. In a further development, the El Nino Southern Oscillation (ENSO) event was divided into six distinct stages. During starting La Nina stage July-August- September (JAS) rainfall of the region was markedly above normal, whereas starting El Nino gave normal rainfall. For both dying La Nina and El Nino markedly below normal rainfall was recorded. As for the well established stages, it is markedly above normal for the well established La Nina and markedly below normal for well established El Nino stage. It was found that the effect of La Nina is direct and concurrent whereas El Nino works with lag-time. In addition to that bad rainy seasons were found to start early. Further studies on the rainfall of Sudan are highly recommended.