Climatic Variability in Central Africa and Its Link to Sea Surface Temperature and the El Nino/La Nina

A diagnostic study of rainfall variability in Africa in the area from 5oS to 10oN and from 10oE to 30oE was carried out using a gauge rainfall data. Emphasis was placed on determining the time-scales of interannual variability, the characteristics of interseasonal fluctuations, and on regionalization of the data. The latter was used in order to reduce the number of regions utilized for studying this variability in the context of sea-surface temperature fluctuations, El Nino/La Nina, and atmospheric circulation variables. Five homogeneous regions were found in this manner. Generally, the most relevant aspects of SST variability for interannual variability of rainfall appear to be: ENSO, Atlantic and Indian Oceans SSTs, Atlantic upwelling and Atlantic dipole. The importance of these varies seasonally and, to a lesser extent, regionally. There is no "symmetry" between the factors associated with wet conditions and those producing dry conditions. Rainfall response to SSTs is clearly seasonally specific. This is manifestation of the complexity of the factors influencing rainfall over Central Africa and of the pronounced seasonality of rainfall over this region. Overall, regions 1, 2 and 3 show strong teleconnection to factors that control variability. For regions 4 and 5 such teleconnections were not found which suggests the possibility that these two regions are not as homogeneous as it appeared initially. One of the reasons for this could be that these two regions represent a transition zone between influences of the Atlantic Ocean to the west and Indian Ocean to the east.