Drought over Zimbabwe in a regional and global context

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Abstract

This study attempts to identify meteorological conditions that lead to dry and wet episodes over Zimbabwe. Correlation analyses are carried out between the Southern Oscillation Index and rainfall over south-eastern central Africa. The results show significant correlation between the Southern Oscillation (SO) and seasonal rainfall over the region. The results also indicate that the SO signal is stronger over the south-east of Zimbabwe and along the coastal areas of Mozambique. El NiñTo events seem to be associated with below normal rainfall over Zimbabwe, while cold events, which are the opposite extreme of the SO, are accompanied by above average rainfall.

Three-month seasonal (December–February) deviations of 1000–mbar temperature, surface pressure, and the 500-mbar geopotential height from the long-term mean are analysed during wet and drought years. The anomaly pressure gradient force is directed towards the subcontinent during wet periods and towards the ocean area during dry episodes. A similar pattern is observed at the 500-mbar level.

A comparison of wet and dry seasons in relation to the temperature anomaly field points to an association between warmer 1000-mbar surface temperatures around the African subcontinent and above normal seasonal rainfall. Correlation analysis shows that a high incidence of tropical cyclones in the Mozambique Channel is associated with below normal rainfall over Zimbabwe.

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