Predictability of the intra-seasonal rainfall characteristics variables over South Africa

Abstract

Aspects of seasonal forecast skill of the SCM and ECHAM4.5 general circulation model (GCMs) are assessed over South Africa. The GCMs output is configured to predict low and high number of rainfall days at South African Weather Service stations exceeding different threshold values for the summer rainy seasons and to predict the onset of the rainy seasons for eight homogeneous rainfall regions of South Africa. Using canonical correlation analysis as statistical downscaling tool the forecast skill levels of both the coupled and uncoupled models are determined through retro-actively generated hindcasts. Both approaches have skill in redicting low and high number of rainfall days exceeding different threshold values for the summer rainy seasons as well as the onset of the rainy seasons for the homogeneous rainfall regions. The purpose of this study is therefore to assess the skill of the state-of-theart forecasting systems in predicting low and high number of summer seasons rainfall days exceeding different threshold values and the onset of the rainy seasons over South Africa.