Physical processes associated with increased summer precipitation in southeastern South America under a warming climate scenario.

Summary Southeast South America (SESA) is one of the few subtropical regions where WCRP/CMIP3 climate models project a significant increase in austral summer precipitation for the late 21st century under a global warming scenario. This signal is associated with an increase in the frequency of summers identified as positive phases of the dominant mode of precipitation variability in the region, this mode being defined by above (below) normal precipitation in the SESA (South Atlantic Convergence Area). This trend is associated with an increase in sea surface temperature (SST) in the equatorial Pacific. This is confirmed by numerical simulation experiments with the LMDZ4 interactive two-way nesting system, which also show that the projected increase in precipitation in the SESA is associated with the zonally asymmetric signal of SST warming.