Moist Convective Scaling: Some Inferences from Three-Dimensional Cloud Ensemble Simulations

Numerical simulations of the tropical atmosphere were performed using a three-dimensional, convection-resolving, nonhydrostatic cloud model, in order to characterize the sensitivity of mesoscale tropical convection to radiative forcing. The system is run into a state of statistical equilibrium for a range of imposed tropospheric radiative cooling rates. The heat budget implies that there should be a larger cloud mass flux for increasing radiative cooling; it does not exclude the possibility of more intense updrafts, but does not require it. In the numerical simulations, it is found that the increase of cloud areal coverage accounts for all the increase of the cloud mass flux required to balance an increase of the radiative cooling rate. At equilibrium, the mean updraft velocity in the clouds is independent of the magnitude of the radiative forcing.