Daily rainfall variability in Southern Africa.

Clear characterisation of daily rainfall over the southern African continent is necessary \nfor the purpose of achieving sustainable human and agricultural-environmental development. \n \nIn this research, daily rainfall variability over southern Africa is investigated to determine \nthe relations between rainfall, rainfall frequency, and amount of rain per rain day. Firstly, \nthe characterisation of daily rainfall over the region from 1950 to 1997 is given. This is \nfollowed by the analysis of daily rainfall variability during the 10 wettest and driest \nyears. Thirdly, the influence of Sep-Nov and Dec-Feb seasons on the 10 wettest and \ndriest years is then highlighted. Lastly, to determine whether the relation between the \nthree rainfall parameters determined over the whole southern African region holds true \nfor local areas, daily rainfall variability over Swaziland during the period of \nmeteorological records is discussed. \n \nAnalyses of daily rainfall over southern Africa indicate that on scales of days to years, \nrainfall departures from mean result from changes in both daily rainfall frequency and \nintensity. Positive rainfall changes are due to an increase in the number of rainy days and \namount of rainfall falling on those rain days. Negative rainfall changes results from a \ndecrease in rainfall frequency and rain falling on those rain days. \n \nSouthern Africa does not show uniform changes in these rainfall variables, but patterns. of \nspatial and temporal variability. This variability increases from the Western regions of the subcontinent (i.e. rainfall variability increases from the eastern humid to the western arid regions of the subcontinent). \n \nThe conclusion is that over the whole of southern African region changes in mean rainfall \nare dependent on the number of rain days and rain per rain day. This result also holds true over smaller areas of the subcontinent, such as Swaziland.