Diagnosis of September - November Drought and the Associated Circulation Anomalies Over Uganda

Ogwang B A, T Guirong, C Haishan


Extreme weather and climate events such as floods and droughts are common in Uganda. These events have always had devastating impacts on various sectors of the country’s economy. In this study we investigate the drought events of September-November (SON) season and the associated circulation anomalies over Uganda for the period 1962-2007. A regional drought index (Z-index) with a scheme of grading severity of drought and flood is used to classify the drought/flood events using station rainfall data. The index successfully classified the drought and flood events, with SON heavy floods (droughts) experienced in the years 1967,1972,1977,1999, 2000 and 2001 (1974 1976,1979,1984,1985 and 1993). Analysis of the drought and flood years with respect to the different variables including wind, velocity potential and divergence/convergence vectors revealed that the drought (flood)
years were characterized by divergence (convergence) in the lower troposphere and convergence (divergence) at the upper level, implying sinking (rising) motion, especially over the western Indian Ocean and the study area. The anomaly convergence zone was identified within (outside) the region of study during flood (drought) years.

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