Impacts of climate variation on the length of the rainfall season: an analysis of spatial patterns in North-East South Africa

摘要

This study examines the impacts of climate variation on the length of the rainfall season in the north-east South Africa (Vhembe District). We first demarcated the area into two major homogeneous rainfall zones namely humid and semi-arid using Principal Component Analysis (PCA). Then we determined the rainfall climatology of each zone in terms of rainfall onset and cessation in view of the emerging climate variation. Sixty years of rainfall data were examined, and a significant decreasing trend in rainfall was observed starting in the 1990s. Generally, the seasonal rainfall onset and cessation are changing, making the rainfall season length shorter. The rainfall characteristics are changing gradually in the humid zone, where it was found that there is a marked change in the onset dates between what it used to be before the 1990s and how it has been since. The rainfall season length has decreased by 50 days. Rainfall characteristics in the semi-arid zone are highly variable with a coefficient of variation (CV) of up to 39 %. Continuous significant decline (at the a parts per thousand yen95 % level) since the mid-1990 suggests that the humid areas will continue to dry while the semi-arid might develop into arid zone. Significant changes were also detected in the cessation of rainfall. In general, the uncertainties and changes in rainfall characteristics add strain on farmers who are faced with the season of inconsistent rain and uncertainties in when to plant their crops. Under these circumstances, it is easy to see how rainfall variation can lead to crop failure and cause food insecurity in the district.