Breaking Rossby waves in a model stratosphere diagnosed by a vortex- following coordinate system and a technique for advecting material contours

Abstract

This paper presents results from a single-layer, shallow-water, 100-day model integration that reproduces many features of the wintertime stratosphere, particularly in the tropics, more realistically than earlier single-layer integrations. The advective transport of passive tracers by breaking Rossby waves is examined using a new polar-vortex-following coordinate system and a technique for advecting material contours, in which they are followed very accurately using the contour-dynamics algorithm of Dritschel. Unlike any Eulerian tracer advection scheme, the technique for advecting material contours has no numerical diffusion and can handle the ultrafinescale, exponentially shrinking tracer features characteristic of chaotic advective transport or "stirring', which is conspicuous here in the stratospheric "surf zone'. -from Author