An energy balance model based on potential vorticity homogenization

It has long been suggested that the extratropical eddies originating in bar oclinic instability act to neutralize the atmosphere with respect to barocl inic instability. These studies focused on the Charney-Stern condition for stability, and since the implication of this condition was the elimination of meridional temperature gradients at the surface, contrary to observation s, there appeared little possibility that the hypothesis was correct. However, Lindzen found that potential vorticity (PV) mixing along isentropi c surfaces accompanied by elevated tropopause height and/or reduced jet wid th could also lead to baroclinic neutralization. Since it is not obvious wh at implications such a neutral state would have for meridional structure of wind and especially temperature, the authors examine, as a first step, in this paper the implications of an assumed fixed PV gradient in the extratro pical troposphere. It is shown that this assumption, combined with an assumption of a moist ad iabatic temperature structure in the Tropics, a constraint on surface stati c stability, and overall radiative equilibrium, suffices to constrain a mod el earth's zonal mean climate. Comparison of the model climate with the obs erved climate, and variation of certain of the model's assumptions to resol ve differences, allow the authors to consider the role of deep convection i n the climate of the midlatitudes. to investigate the connection between su rface turbulent heat fluxes and meridional energy fluxes carried by barocli nic eddies, and to deduce the role of the stratosphere's overturning circul ation in determining the height of the tropopause.