Uganda rainfall variability and prediction
This study analyzes large-scale controls on Uganda’s rainfall. Unlike past work, here, a May–October season is used because of the year-round nature of agricultural production, vegetation sensitivity to rainfall, and disease transmission. The Uganda rainfall record exhibits steady oscillations of ∼3 and 6 years over 1950–2013. Correlation maps at two-season lead time resolve the subtropical ridge over global oceans as an important feature. Multi-variate environmental predictors include Dec–May south Indian Ocean sea surface temperature, east African upper zonal wind, and South Atlantic wind streamfunction, providing a 33% fit to May–Oct rainfall time series. Composite analysis indicates that cool-phase El Niño Southern Oscillation supports increased May–Oct Uganda rainfall via a zonal overturning lower westerly/upper easterly atmospheric circulation. Sea temperature anomalies are positive in the east Atlantic and negative in the west Indian Ocean in respect of wet seasons. The northern Hadley Cell plays a role in limiting the northward march of the equatorial trough from May to October. An analysis of early season floods found that moist inflow from the west Indian Ocean converges over Uganda, generating diurnal thunderstorm clusters that drift southwestward producing high runoff.
Data were analyzed from the KNMI Climate Explorer, IRI Climate Library, NASA Giovanni, Univ Hawaii APDRC, NOAA Ready ARL, and FAS USDA Crop Explorer websites. This work contributes to the Rockefeller Foundation project on climate resilience via the Ethiopia Institute for Agriculture Research in Melkassa.
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