A simple radiative-convective model with a hydrological cycle and interactive clouds

We have developed a simple, analytically tractable radiativexonvective model of the tropical climate system that includes an explicit moisture budget, a simple convection parametrization, a simple but physically based radiation parametrization, and interactive clouds. The underlying surface is assumed to be ocean. The model includes prognostic equations for the sea surface temperature and the vertically integrated water vapour content. A stratosphere in radiative equilibrium limits the depth of the convective layer. The lower-tropospheric lapse rate, surface evaporation rate, and clear-sky long-wave and short-wave radiative fluxes at the surface and the top of the atmosphere are determined as functions of the sea surface temperature and precipitable water only. The radiativeconvective equilibria of the model atmosphere resemble the observed tropical climate, if realistic sea surface temperatures are prescribed. However, cloud-free radiativexonvective equilibria of the tropical atmosphere-ocean system do not occur for realistic values of the surface albedo. When cloud radiative effects are included, the model produces radiativexonvective equilibria that are unrealistically warm. With prescribed realistic lateral energy and moisture transports, however, the equilibria of the model are realistic.