The
Enhancement of Rossby Wave Breaking by Steep Potential
Vorticity Gradients in the Winter Stratosphere
Dr. Richard Scott
Department of Applied
Physics and Applied Mathematics
Abstract:
The talk will illustrate the extent to which potential
vorticity gradients affect the vertical propagation
of planetary scale Rossby waves on the edge of a
stratospheric polar vortex and their eventual nonlinear saturation and
breaking. Using two different numerical modeling approaches, we show that
wave propagation and wave breaking is significantly reduced when the potential vorticity gradients at the vortex edge are weak, compared
with when they are strong. The efficiency of the first model, based on high
resolution contour dynamics, permits a full exploration of the parameter space
of wave forcing amplitude and edge steepness. A more realistic primitive
equation model in spherical geometry both confirms the contour dynamics results
and highlights some direct implications for stratospheric modeling in more
comprehensive models. The results suggest that stratospheric models using
horizontal resolutions of spectral T42 or less may significantly underestimate
the vertical propagation and breaking of planetary waves, and consequently misrepresent
such important stratospheric processes as the mean meridional
circulation and the mixing of chemically distinct polar and midlatitude
air.