ENSO-like decadal variability and South African rainfall

Abstract

Decadal to multidecadal 'ENSO-like' SST and circulation patterns in joint EOFs of global SST and MSLP, may be linked to South African rainfall variability. For eastern/northern South Africa (summer rainfall), the average of the 9-13 year and 18-39 year bandpass filtered EOFs tracks the rainfall well for 1903-1998. Higher (lower) pressure, warmer (cooler) SST in the Pacific and Indian Oceans and offshore (onshore) winds characterise the positive (negative) EOF signal and decreased (increased) rain. For southwestern South Africa (winter rainfall), the average of the 13-18 and 18-39 year filtered EOFs tracks the rainfall well from 1903-1982 with the 9-13 year EOF working better from 1983-1998. The suggested mechanism involves shifts in the upper level jet and in the strength of the subtropical high pressure belt and circumpolar trough.