An Analysis of Thermally-Related Surface Rainfall Budgets Associated with Convective and Stratiform Rainfall

Both water vapor and heat processes play key roles inproducing surface rainfall. While the water vapor effects of seasurface temperature and cloud radiative and microphysical processeson surface rainfall have been investigated in previous studies, thethermal effects on rainfall are analyzed in this study using aseries of two-dimensional equilibrium cloud-resolving modelexperiments forced by zonally-uniform, constant, large-scale zonalwind and zero large-scale vertical velocity. The analysis ofthermally-related surface rainfall budget reveals that the modeldomain mean surface rain rate is primarily associated with the meaninfrared cooling rate. Convective rainfall and transport ofhydrometeor concentration from convective regions to rainingstratiform regions corresponds to the heat divergence overconvective regions, whereas stratiform rainfall corresponds to thetransport of hydrometeor concentration from convective regions andheat divergence over raining stratiform regions. The heat divergenceover convective regions is mainly balanced by the heat convergenceover rainfall-free regions, which is, in turn, offset by theradiative cooling over rainfall-free regions. The sensitivityexperiments of rainfall to the effects of sea surface temperatureand cloud radiative and microphysical processes show that the seasurface temperature and cloud processes affect convective rainfallthrough the changes in infrared cooling rate over rainfall-freeregions and transport rate of heat from convective regions torainfall-free regions.