Baroclinic Adjustment and Dissipative Control of Storm Tracks

Abstract

The steady-state response of a midlatitude storm track to large-scale extratropical thermal forcing and eddy friction is investigated in a dry general circulation model with a zonally symmetric forcing. A two-way equilibration is found between the relative responses of the mean baroclinicity and baroclinic eddy intensity, whereby mean baroclinicity responds more strongly to eddy friction whereas eddy intensity responds more strongly to the thermal forcing of baroclinicity. These seemingly counterintuitive responses are reconciled using the steady state of a predator–prey relationship between baroclinicity and eddy intensity. This relationship provides additional support for the well-studied mechanism of baroclinic adjustment in Earth’s atmosphere, as well as providing a new mechanism whereby eddy dissipation controls the large-scale thermal structure of a baroclinically unstable atmosphere. It is argued that these two mechanisms of baroclinic adjustment and dissipative control should be used in tandem when considering storm-track equilibration.