Onset of Edge Wave Breaking in an Idealized Model of the Polar Stratospheric Vortex

Abstract

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, quasigeostrophic 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.