Long-term variations in winter rainfall of southwest Australia and the African monsoon

Abstract

The rainfall of southwest Western Australia (SWWA) suffered a 20 per cent long-term decrease in the late 1960s, which continues to the present day. This change approximately coincides with the well-known long-term decrease of rainfall in the African Sahel. It is shown here that these two-substantial changes appear to be connected by conventional atmospheric dynamics, the former change being a consequence of the latter, as follows. The decrease in the Sahel rainfall and intensity of the African monsoon in the southern hemisphere winter (June, July, August) caused a corresponding decrease in the transport in the upper-level Hadley cell west of Africa. This in turn caused a decrease in the tran..