Large-scale variability of atmospheric deep convection in relation to sea surface temperature in the tropics

Empirical relationships between tropical sea surface temperature (SST) and atmospheric deep convection are examined. Large-scale features of tropical deep convection are estimated from two independent satellite datasets: monthly mean outgoing longwave radiation of 15 years and high-resolution pentad (5 day) fractional coverage of infrared radiation histograms of 5 years. Results based on the two datasets lead to the same conclusions. Deep convection remains weak and rarely observed for SST <26°C; the frequency and mean intensity of deep convection substantially increase with SST from 26°C up to about 29.5°-30°C, and then decay for further increasing SST. Meanwhile, in the warm pool region with SST >27°C, situations of no deep convection and vigorous deep convection can both be observed; the areal coverage of convectively related high clouds is always dominated by that of clear sky and low clouds. The variability of deep convection, thus becomes larger for higher SST. -from Author