Browsing by Author "Walawege, Ruwani Priyanthika"

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    An examination of the spatially extensive heavy precipitation events over South Africa and the associated moisture trajectories
    (2002) Walawege, Ruwani Priyanthika; Hewitson, Bruce
    Precipitation is possibly the most important climatic variable in southern Africa. The absence of a good rainy season is often marked with low productivity and in some cases starvation. However, excessive rainfall can also bring with it disaster and destruction. Investigating the causes of such events has been the aim of a number of studies in the past. The interest shown in extreme events, including that of precipitation has been growing in the last couple of years. This comes as a result of understanding that the change in the mean of variables can have a large influence on the extremes of these same variables. In fact, changes in the extremes can be disproportionate and often have more impact on both society and the environment. This raises concerns especially in poorer nations who often lack the financial resources to deal with such impacts. The primary aim of the present study is to investigate spatially extensive heavy precipitation events in South Africa. It explores the possible spatial patterns that exists within these events and also investigates the non-local sources of moisture for them. In order to do this, the study firstly utilises a categorisation technique called Self Organising Maps (SOMs). A number of groups were identified through this process and sample events from this were then further analysed with the use of a kinematic trajectory model. The results indicated that moisture for these events were most likely to be transported from the south Indian Ocean. Although this finding has been shown previously in other similar studies, the present investigation shows that the possible source of moisture to be further south that previously thought. Further investigation was done by examining a case event more closely. The results also show that an area in the south Indian Ocean, east of Madagascar to be the possible source of moisture for this particular event.