Tropical heat/water vapor quasi-equilibrium and cycle as simulated in a 2D cloud-resolving model

Abstract

The heat/water vapor equilibrium and cycle in the tropical deep convective regime are analyzed using a two-dimensional cloud-resolving simulation. The model is forced by the large-scale vertical velocity, zonal wind and large-scale horizontal advection derived from Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) for a 20-day period. The analysis shows a near perfect balance between vertical thermal advection and latent heat of condensation in the mass-weighted mean heat budget and between vertical moisture advection and precipitation in the precipitable water budget. The local changes of mass-weighted mean temperature and precipitable water are mainly determined by the heat and moisture residuals, respectively. The error analysis shows that the error of the local thermal and moisture changes could be 5–10 times larger than the errors introduced by the condensation and vertical advections. The condensation and associated latent heat determine local moisture loss and thermal gain for strong convection, whereas the vertically advective moistening and cooling cause local moisture gain and thermal loss for weak convection, forming a tropical heat/water recycling mechanism. The enhanced rainfall associated with the convection consumes the instability energy and moisture source, and causes the decay of convection. The suppression of convection allows the restorations of CAPE and moisture source for the favorable conditions of development of convection.