On the relative influences of different ocean basin sea surface temperature anomalies on southern African rainfall in 20th and 21st century general circulation model simulations

摘要

Southern Africa rainfall (SAR) is generally projected to decrease during the 21st century as a result of climate change, although there is some disagreement regarding the location and magnitude of this reduction in general circulation models (GCMs). Here we examine the robustness of the rainfall response to sea surface temperature (SST) anomalies. Previous work argues that warmer SSTs in the Indian Ocean suppress SAR. Other studies argue that El Nino leads to suppressed SAR. We examine the SAR response to SST anomalies in the Indian Ocean, Atlantic Ocean, and Nino3.4 region both in observations and in two large ensembles of GCMs run over the 20th and 21st century. We find that El Nino-Southern Oscillation (ENSO) SSTs are most correlated with SAR, while correlations between SAR and the Indian Ocean are dominated by their respective responses to ENSO. This relationship appears to persist under a warming background state.