On the formation and maintenance of the stratospheric surf zone as inferred from the zonally averaged potential vorticity distribution

The diagnostic relation between eddy potential vorticity flux and Eliassen-Palm flux convergence in the transformed Eulerian mean shallow-water system is used to infer the flux convergence needed to establish a stratospheric surf zone comprising a single region of perfectly homogenized potential vorticity, or to maintain the surf zone in steady state against the restoring effect of radiative relaxation. In the transient case, and when wave breaking is assumed to mix potential vorticity on time-scales shorter than the radiative time-scale, the required flux convergence is an order of magnitude larger than that required to maintain the flow in steady state away from radiative equilibrium.