A Note on the Baroclinic Instability of General Time-Dependent Basic Fields of the Eady Type

Abstract

The Eady problem concerning the stability of quasi-geostrophic baroclinic flows which have uniform vertical shear is generalized to include time-dependent basic flows. By means of a simple transformation an exact solution can be obtained. The instability of the flow, in the sense of boundedness as t ? ∞, is determined by the usual Eady criterion derived for steady basic flows, but the growth rates can be significantly enhanced or diminished. In the special case of purely periodic time dependence, the flow is always stable in the above sense.