CONVECTIVE CLOUD SYSTEMS AND WARM-POOL SEA-SURFACE TEMPERATURES - COUPLED INTERACTIONS AND SELF-REGULATION

Questions regarding the upper limits on tropical sea surface temperatures and the processes determining those limits have recently come under renewed interest and debate. We present results from an analysis of the relationship between observed sea surface temperature (SST) and organized deep convection in the tropics that has produced new and important findings relevant to this issue. First, the analysis reveals that the highest observed tropical SSTs are generally associated with diminished convection. Second, the maximum convective activity occurs, on average, at an SST of about 29.5-degrees-C. Third, at SSTs of about 29-degrees-C and greater, intense deep convection is associated with ocean surface cooling of approximately 0.1-degrees-C per month, while suppressed deep convection is associated with a similar degree of ocean surface warming. These three findings, together with results from simplified model analyses, emphasize the importance of the cooling mechanisms associated with deep convection in determining the observed upper limits on tropical SST. Implications of the observed relationship between deep convection and SST on the temporal correlations between these fields is discussed, as is the convective cloud system's relative influence on the solar and evaporative heat flux components of the surface energy budget.