Convective mass as a predictor of rainfall in the tropics and subtropics

The purpose of this work is to explore the extent to which thermodynamics can predict the seasonal variation of rainfall at various tropical and subtropical locations. In this work monthly mean convective mass was calculated from 12 tropical and 4 sub-tropical locations. Convective mass is the amount of mass in the boundary layer, which is able to take part in deep convection due to its positive convective available potential energy. It is found that high convective mass is associated with high rainfall rates while low convective mass is associated with low rainfall rates. The correlation coefficient between convective mass and SST is higher in subtropical locations than in tropical locations. The seasonal variation of convective mass is similar to that of SST in subtropical locations, while in the tropics the sites with the largest differences between maximum and minimum SST's follow the seasonal cycle of SST. Thermodynamics set the conditions required for persistent active deep convection. There appears to be a threshold convective mass required to generate large rainfall rates. (Abstract shortened by UMI.)...