The Roles of Mean Meridional Motions and Large-Scale Eddies in Zonally Averaged Circulations

Abstract A hierarchy of zonally averaged atmospheric models is used to study the role of mean meridional motions and large-scale eddies in determining the zonal climate. Five models are developed: a radiative-convective equilibrium model (no large-scale motion), a zonally uniform model (no longitudinal asymmetries), an energy balance model (parameterized energy transport), a model that combines the physics of the two previous models, and a full statistical-dynamic model (with parameterizations of eddy momentum transport as well as eddy sensible heat transport). In the most complete model, the zonally averaged primitive equations are solved after parameterizing the eddies, friction and the diabatic heating rates. All the models have two layers in the vertical and a latitudinal grid resolution of 5°. For simplicity, we treat a “dry earth” case and calculate annual-average equilibrium states with each of the five models. We find that in the tropics a parameterized energy transport commonly used in energy bal...