Climate Variability and Change—Hydrological Impacts (Proceedings of the Fifth FRIEND World
Conference held at Havana, Cuba, November 2006), IAHS Publ. 308, 2006, 362–368.
Influences of ENSO and SST variations on the interannual
variability of rainfall amounts in southern Africa
PATRICK VALIMBA1, PIERRE CAMBERLIN2, YVES RICHARD2, ERIC
SERVAT3 & DENIS HUGHES4
1 Department of Water Resources Engineering, College of Engineering and Technology, University of Dar Es Salaam, PO Box 35131, Dar Es Salaam, Tanzania
pvalimba@hotmail.com
2 UMR 5080 CNRS Centre de
Recherches de Climatologie, Université de Bourgogne, 6 Bd Gabriel, F-21 000
Dijon, France
3 IRD, UMR HydroSciences, Maison de Sciences de
l’Eau, Université Montpellier II, BP 64501, F-34394 Montpellier cedex 5, France
4 Institute for Water Research, Rhodes
University, PO Box 94, Grahamstown 6140, South Africa
Abstract Relationships
between southern Africa rainfall, the El Niño-Southern Oscillation (ENSO) and
sea surface temperatures (SSTs) were investigated. Principal Components
Analysis (PCA) on rainfall amounts established coherent regions. Results of
correlation analysis between rainfall and the Southern Oscillation Index (SOI)
and regional SST anomalies indicated strong influences of ENSO and the Tropical
Indian Ocean and moderate influences of the Southwest Indian Ocean. The ENSO
influence was consistently, moderately negative in equatorial Southern Africa
during October–January, strongly positive in the Tropical/Subtropical areas
during February–April and highest for light and moderate events in the south
and for intense events in the north. SSTs in the Tropical Indian Ocean
influence light and moderate events, while SSTs close to the region influence
heavy events. Sliding correlations indicated changing rainfall–SOI/SST
relationships in the mid-1950s which improved the associations, and since the
early-1970s which deteriorated or reversed the relationships.
Key words
rainfall
variability; ENSO; SST; Principal Components analysis; correlation analysis