Interaction between Extratropical Stationary Waves and the Zonal Mean Circulation

Abstract

A troposphere–stratosphere simple GCM that simulates the wintertime general circulation with considerable accuracy is presented. The model is driven by temperature relaxation, additional prescribed tropical heating, self-induced heating in midlatitudes, and boundary layer mixing. The idealizations in diabatic heating are used to study the basic impacts of orographic and midlatitude thermal forcing of stationary waves on the zonally averaged northern winter climatology in the troposphere. It is found that large-scale mountains in the winter hemispheric midlatitudes do generally lead to enhanced eddy feedback onto the Hadley circulation; that is, the tropical streamfunction maximum is reduced and the surface near equatorward flow is enhanced due to enhanced eddy heat flux from the subtropics into midlatitudes. In addition, the subtropical jet is reduced and shifted poleward due to enhanced eddy deceleration in the poleward branch of the Hadley cell. A prescribed longitude dependence of self-induced heating in the winter extratropics gives rise to quite an opposite response with regard to Hadley cell, subtropical Eliassen–Palm flux divergence, and eddy heat flux from the subtropics into midlatitudes. The subtropical jet is displaced equatorward and the overall wave activity shifts poleward. These effects depend on the nonlinear nature of self-induced midlatitude heating.