Decadal changes in tropical convection suggest effects on stratospheric water vapor

Abstract

Analysis of satellite observations of tropical Weather States derived from a cluster analysis of ISCCP cloud property retrievals, shows that the deep convection Weather State increased in frequency from 1983 to about 2000 and remained at a nearly constant level after that. The sharpest deep convection increase occurred between 1993 and 2000. This convection variability is driven by changes that occur in the Indian Ocean and the Western‐Central Pacific regions, which are the regions where the majority of deep tropical convection occurs. Analysis modifications to account for satellite coverage changes during the period under examination do not alter these findings. Previous studies showed that stratospheric water vapor increased from 1980 to 2000 and dropped after that to lower levels that persist until today, and that this change could explain part of the recent global temperature variability. Since tropical deep convection is an important mechanism affecting stratospheric water vapor concentrations, the observed decadal changes in tropical deep convection could explain in part the stratospheric water vapor variability patterns.