| We formulate a simplified moist general circulation model (GCM) and use this model to study several topics in the moist general circulation of the atmosphere. The model consists of the full primitive equations on the sphere, with simplified physical parameterizations which isolate certain climate feedbacks and facilitate simulation over a wide range of parameters. A key simplification is the use of grey radiative transfer, in which water vapor and other constituents have no effect on radiative fluxes.; We first consider a set of experiments with no convection scheme (large scale condensation only) and study the effect of moisture on midlatitude static stability, eddy scales, and energy transports (this section is in collaboration with Isaac Held and Pablo Zurita-Gotor). We vary the moisture content of the atmosphere over a wide range, from dry to 10 times the moisture of the current climate, by varying a parameter in the Clausius-Clapeyron equation. In these simulations, the midlatitude static stability is found to be remarkably neutral with respect to moist convection. Despite the large changes in dry stability as the moisture content is increased, the eddy length scales in the simulations remain nearly constant, a fact we interpret with the Rhines scale at the jet latitude. Finally, as moisture content is increased, the poleward fluxes of energy are remarkably constant as well, indicating a high degree of compensation between dry static energy fluxes and moisture fluxes (the compensation is 99% from the control case to the dry limit). We interpret these findings with energy balance models, including a model with exact compensation, and a model which predicts the jet latitude and strength, and moist static energy diffusivity.; We then shift our focus to the tropics, first by deriving a one-dimensional model to study the effect of moisture on large-scale dynamics on the equator. We use this to formulate a theory for "precipitation fronts" in the tropical atmosphere, which mark the boundary between precipitating and non-precipitating regions in the tropics. This section is in collaboration with Andy Majda and Olivier Pauluis.; As the tropical circulation in the GCM is somewhat unrealistic with no convection scheme, we develop a simplified convection scheme in the style of Betts and Miller (1986) and study the effects of this scheme and its parameters on the zonally averaged circulation in the tropics. We find that a key categorization of convection schemes is whether these can build up and rapidly release convectively available potential energy. The formulation of some kind of shallow convection scheme is important in determining this behavior. |
