Trimodal cloudiness and tropical stable layers in simulations of radiative convective equilibrium

Abstract

In this paper, we examine the tropical environment at radiative convective equilibrium using a large-domain cloud system resolving numerical model. As in observed studies of convectively active periods over warm tropical oceans (in particular the tropical western Pacific), we find a trimodal cloud structure that is closely associated with the presence of three distinct stable layers, including a prominent stable layer located near the zero-degree Celsius level. In addition, the simulation exhibits three separate large scale zonal overturning circulations, with two of these circulations located above the trade wind inversion and separated by the freezing level stable layer. At equilibrium, latent heat release associated with freezing and melting processes is dwarfed by that of vapor transitions, and simulation results suggest that this stable layer can be maintained by subsidence in the presence of longwave radiative cooling above the zero-degree level. Copyright 2008 by the American Geophysical Union.