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

Abstract

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