Influence of Cloud Radiation Feedback on the Uncertainty in Projecting Tropical Pacific SST Warming Pattern

Abstract

The role of inter-model spreads of the cloud radiation feedback on the uncertainties of tropical Pacific SST warming (TPSW) pattern is investigated in this chapter. The large inter-model discrepancies of the cloud radiation feedback over the central Pacific, which appear to be the leading source of inter-model uncertainty in the TPSW pattern, contribute 24% of inter-model variance in the TPSW pattern with a peak over the western and central Pacific. The influence mechanism of the cloud radiation feedback on the TPSW pattern is revealed based on the surface heat budget analysis. A relatively weak negative cloud radiation feedback over the central Pacific can induce a warm SST deviation over the central Pacific, producing a low-level convergence on the equatorial Pacific that suppress (enhance) the evaporation cooling and zonal cold advection in the western (eastern) Pacific. With the processes, the original positive SST deviation over the central Pacific will move westward to the western and central Pacific with a negative SST deviation in the eastern Pacific. A group of model experiments with a coupled ocean–atmosphere model further verifies this mechanism of impact.