Nonlinear Processes in Oceanic and Atmospheric Flows

Presentation

Nonlinear geostrophic adjustment in the presence of frontal and topographic waveguides

Author: E. Scherer, Laboratoire de Météorologie Dynamique, Ecole Normale Supérieure & Université Paris VI.

Names and affiliation of other authors:
F. Bouchut, Département de Mathématiques et Applications, ENS, Paris, France
J. Le Sommer, LEGI, Grenoble, France
V. Zeitlin, Laboratoire de Météorologie Dynamique, ENS, Paris, France

Oral or poster: Poster

Abstract:
Geostrophic adjustment, well-known in an infinite fluid, is modified in the presence of waveguides. Waveguides are ubiquitous in the ocean and in the atmosphere: varying topography (marine / mountains) and density fronts. We present the modification of the scenario of geostrophic adjustment in the presence of three waveguides: the topographic waveguide, the midlatitude frontal waveguide and the equatorial frontal waveguide. We used the rotating shallow water model and finite volume numerical methods adapted to treat the topography and the incropping/outcropping of fronts. In all cases, generation of trapped waves takes place and the nonlinear evolution of the trapped waves depend on the dispersive properties of the trapped waves. Dispersive waves like the topographic Rossby waves, or the waves propagating along the midlatitude frontal waveguide, reconnect streamlines, altering the transport properties of the flow. We show that the dynamical splitting between slow/balanced and fast/unbalanced motions, known in free flow, is always effective in the presence of these waveguides.
Réf:
- Le Sommer, Scherer & Zeitlin, J. Phys. Ocean, 2006
- Bouchut, Scherer & Zeitlin, Phys. Fluids, 2008
- Scherer & Zeitlin, to appear in J. Fluid Mech.

*Satellite images from NASA and ESA

Nonlinear Processes in Oceanic and Atmospheric Flows. July 2-4, 2008. Castro Urdiales, Cantabria, Spain.