Rainfall variability over Zimbabwe and its relation to large-scale atmosphere-ocean processes

Abstract

The relationship between interannual variability of Zimbabwe rainfall and atmosphere-ocean interaction processes is established using high-resolution rainfall station datasets. Empirical orthogonal function (EOF) analysis is used to extract the spatiotemporal modes that explain most of the variations in the rainfall pattern. Results suggest strong homogeneity in the rainfall pattern that is dominantly described by EOF mode 1. The correlation analysis of mode 1 with sea surface temperatures (SSTs) supports the assumption that El Nino Southern Oscillation (ENSO) has a significant influence on Zimbabwe summer rainfall. Significant correlations exist between rainfall and SSTs over large regions of the tropical Indian and Pacific Oceans. The seasonal response of rainfall to the southern annular mode is reflected in both modes 1 and 2. Mode 1 suggests homogeneity in rainfall variations within the country and mode 2 describes the north-south rainfall fluctuations in the country. Although the magnitudes of their loadings are small, modes 3 and 4 extracted distinct rainfall regions within the country. This could be attributed to the use of more reliable, higher resolution rainfall data. These findings will assist to bring profound improvements to seasonal rainfall forecasting techniques around the country.