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

Journal Article · Tue Feb 15 04:00:00 EST 1994 · Journal of the Atmospheric Sciences; (United States)

DOI:https://doi.org/10.1175/1520-0469(1994)051<0654:BRWIAM>2.0.CO;2· OSTI ID:6912565

Norton, W A ^[1]

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1. Univ. of Cambridge (United Kingdom)

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' surfzone.' The technique may become important as a benchmark for quantitative comparison with Eulerian tracer advection schemes, such as those used in general circulation models. Averages with respect to the vortex-following coordinate system give a clearer picture of the gross features of the tracer transport than conventional Eulerian zonal averages, because the reversible displacements associated with undulating Rossby waves are largely eliminated. Results indicate that the edge of the polar vortex acts as a flexible, Rossby elastic' barrier to eddy transport of air from the surf zone into the vortex, with air well inside the vortex completely isolated for the entire 100 days. This last point is precisely demonstrated by results from the technique for advecting material contours. Erosion of material from the vortex during days 30 to 100 of the model integration was not more than about 16% of the area of the model's surf zone, counted as the area between 30[degrees]N and 60[degrees]N. The model integration also shows, more realistically than earlier single-layer integrations, a partial barrier to exchange of air between the tropics and middle latitudes.

• OSTI ID: 6912565
• Journal Information: Journal of the Atmospheric Sciences; (United States), Journal Name: Journal of the Atmospheric Sciences; (United States) Vol. 51:4; ISSN 0022-4928; ISSN JAHSAK
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics &amp; Computers
ATMOSPHERIC CIRCULATION
CRYOSPHERE
EARTH ATMOSPHERE
MATHEMATICAL MODELS
POLAR REGIONS
STRATOSPHERE
VORTICES