J. Atmos. Sci. , 73, 199-209.
Usama Anber
Department of Earth and Environmental Sciences,
Columbia University, New York, NY.
Shuguang Wang
Department of Applied Physics and Applied Mathematics,
Columbia University, New York, NY.
Adam H. Sobel
Department of Applied Physics and Applied Mathematics, and Lamont-Doherty Earth Observatory,
Columbia University, New York, NY.
Abstract
The authors investigate the effects of cloud-radiation interaction and vertical wind shear on convective ensembles interacting with large scale dynamics in cloud resolving model simulations, with the large-scale circulation parameterized using the weak temperature gradient approximation. Numerical experiments with interactive radiation are conducted with imposed surface heat fluxes constant in space and time, an idealized lower boundary condition which prevents wind-evaporation feedback. Each simulation with interactive radiation is compared to a simulation in which the radiative heating profile is held constant in the horizontal and time, and is equal to the horizontal mean profile from the interactive radiation simulation with the same vertical shear and surface fluxes. Interactive radiation is found to reduce mean precipitation in all cases. The magnitude of the reduction is nearly independent of the vertical wind shear, but increases with surface fluxes. Deep shear also reduces precipitation, though by approximately the same amount with or without interactive radiation. The reductions in precipitation due to either interactive radiation or deep shear are associated with large-scale descent in the lower troposphere, which more strongly exports moist static energy and is quantified by a larger normalized gross moist stability.