On the Relationship between Tropical Convection and Sea Surface Temperature

Tropical observations show convective activity increasing sharply above sea surface temperatures (SSTs) of around 26°C and then decreasing as the SST exceeds 30°C, with maximum observed SSTs of around 32°C.Although some aspects of this relationship are reasonably well understood, as of yet no theory has explained the decrease in convective activity above 30°C. Here it is suggested that this aspect of the relationship could result from a organizational positive feedback, sometimes termed “self aggregation,” whereby the occurrence of convection makes future convection more likely to occur in the same location. Using cloud-resolving simulations, it is shown that the feedback between convection and the water vapor field is a good candidate for this role.