Vortex Flows and Related Numerical Methods II
ESAIM: Proceedings,
Vol. 1, 1996, pp. 481-501
Vortex Expulsion by a Zonal Coastal Jet
on a Transverse Canyon
Laurent M. Chérubin and Xavier J. Carton
David G. Dritschel
DAMTP, University of Cambridge, Cambridge, UK
Abstract
Recent observations of subsurface-intensified, alongshore slope-currents
have shown vortex formation over a transverse canyon, in the Gulf of
Cadiz. To analyze this process, we idealize this situation to a zonal
coastal jet, with piecewise-constant potential-vorticity, flowing over a
meridionally sloping bottom. We analytically calculate the linear
barotropic and baroclinic stability of the flow in the quasi-geostrophic
framework (in the absence of the canyon). Several physical and geometrical
cases are considered. The effect of an additional transverse canyon is
simulated numerically using the two-dimensional contour-surgery code. It
is shown that
- a double strip of vorticity is linearly unstable and a very shallow
canyo is sufficient to provoke wave growth on the vorticity interfaces;
these waves nonlinearly sat rate into a dipolar vortex;
- a single active vorticity region is linearly stable, but a deep enough
ca yon can trigger various nonlinear responses (waves, filaments, vortex
detachment, turbulence).
The relevance of such an idealized model to real oceanic cases is finally
discussed, its shortcomings are highlighted, and possible improvements are
suggested for futur work.
Vortex Flows and Related
Numerical Methods II
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