An investigation into the relative contributions of ENSO, Benguela Niño and the sub-tropical Indian Ocean dipole on summer rainfall over southern Africa

Master Thesis


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University of Cape Town

The region below the 5ᵒS latitude is defined here as southern Africa. This region is subject to high inter-annual rainfall variability attributed to the local and remote SST fluctuations. The main purpose of this study is to investigate the unique impact that SST conditions related to ENSO, Benguela Niño and subtropical Indian Ocean Dipole (SIOD) has on summer rainfall over southern Africa. To achieve this, a partial correlation method was employed to analyse the possible relationship between rainfall variability and interannual SST variability in the Niño3.4 index, Angola-Benguela front and SIOD index for the climatological period between 1950 and 2010. The results revealed ENSO as a prime mode of rainfall variability in southern Africa. The ENSO-rainfall relationship in the central region of southern Africa tends to be modulated by the Benguela Niño and SIOD signal. In the west coast region of Namibia and Angola, the Benguela Niño was found to be strongly linked to rainfall variability. However, this Benguela Niño-rainfall relationship tends to weaken when the effect of ENSO and SIOD is removed. The SIOD impact on the rainfall was found to be dependent on ENSO.

Includes bibliographical references.