A detailed rainfall climatology for Malawi, Southern Africa

摘要

This article presents a detailed analysis of the mean rainfall climatology of Malawi and an overview of interannual variability. Monthly and seasonal means, the seasonal cycle and intraseasonal variability are examined. This includes an analysis of the onset, end and duration of the rainy season. The study reveals two surprising features of the rainfall regime. One is a region with a strong rainfall maximum in the austral autumn along the western shore of Lake Malawi. The second is a brief period of reduced rainfall in mid-February that appears to signal a shift in the prevailing rainfall and circulation regime. The prevailing atmospheric circulation is markedly different before and after the break, as are the characteristics of the rainy season. Overall, the results indicate that the early (pre-break) rainy season (December-February) is dominated by tropical influences, the late (post-break) rainy season (March-April) is dominated by extra-tropical influences and interannual variability in these two periods is uncorrelated. The results also demonstrate two aspects of interannual variability: the dominant contribution of the MA season and the frequent opposition between northern and southern Malawi.