A mechanism for the breakdown of vertically-propagating edge waves in a Boussinesq fluid is investigated within the context of the destruction of the polar stratospheric vortex. Under inviscid, quasi-linear and slowly-varying conditions in a three-dimensional, quasi-geostrophic Contour Dynamics model it is analytically predicted that planetary-scale edge wave breaking will occur if the zonal mean flow is decelerated by more than approximately one-half its initial value via a positive group-velocity/mean-flow feedback mechanism. Fully nonlinear model simulations confirm this "one-half rule" and detail the sequence of events leading to the breaking.
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12th Conference on Atmospheric and Oceanic Fluid Dynamics