Using a multilayer quasigeostrophic model, we investigate the response of an idealized baroclinic polar vortex to topographically forced Rossby waves. We consider a number of initial potential vorticity configurations, and describe under which circumstances the wave breaking is confined to the bottom part of the vortex. In contrast to the findings of Dritschel & Saravanan (Q.J.R.M.S., vol. 120, 1994) for a barotropic vortex, we show that low-level wave breaking can occur even at small forcing amplitudes. We construct a kinematic interpretation of this behavior in terms of the distance between the polar vortex edge and the stagnation points of the flow. We discuss the relevance of these results to the maintenance of stratopsheric polar "sub-vortex".
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12th Conference on Atmospheric and Oceanic Fluid Dynamics