The influence of sea surface temperatures on Ugandan rainfall

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Monday, 18 January 2010
Exhibit Hall B2 (GWCC)
Saul Daniel Ddumba, Makerere University, Kampala, Uganda

Uganda's rainfall is controlled by large scale patterns and synoptic-scale weather features such as the Inter Tropical Convergence Zone (ITCZ), monsoons, meso-scale circulations, subtropical anticyclones and teleconnections. This study focused on the influence of sea surface temperatures (SSTs) on Uganda's March-May (MAM) and September-November (SON) rains. The data used included the NCEP/NCAR reanalysis data set and monthly rainfall totals from the Uganda Meteorological Department. The correlation and regression analysis was performed using a model managed by the NCEP center giving the following results. The SON rains showed a strong relationship (r=0.6) with SSTs in the Pacific and Indian Ocean while the MAM rains showed a weaker relationship (r= 0.4) with SSTs in the Pacific and Indian Ocean. There was no significant relationship between the rains and the Atlantic Ocean SSTs. It was noted that the strong relationship of SON rains and SSTs in the Pacific can be used for running seasonal rainfall forecasts. The MAM rains showed a weak relationship thus implying that other controlling factors other than SSTs could be more responsible for the rains in that season. It was recommended that the application of Global Climate Models and Regional Climate Models in forecasting Uganda's rainfall to be encouraged and taken up by the National Meteorological Centre.