Influence of a Strong Bottom Slope on the Evolution of a Surface-Intensified Vortex

Abstract

The authors investigate the influence of steep bottom topography on the propagation of a vortex in a two-layer quasigeostrophic model. The vortex is intensified in the upper layer and the planetary beta effect is taken into account. The authors find that steep topography can scatter disturbances created by the upper-layer vortex displacement and maintain the lower-layer motion weak. It is thus shown that, when the vortex radius is smaller than a critical value, the vortex behaves as if the lower layer was at rest (or infinitely deep as in a reduced gravity model). If the radius is increased while holding the maximum vorticity of the vortex, the topographic Rossby waves?generated during the scattering process?have a stronger signature in the upper layer, and the vortex evolution begins to change in comparison with the reduced-gravity case. However, numerical experiments show that both the steep topography and reduced-gravity trajectories remain close up to a large radius, after which a vortex above a strong slope becomes unstable and is dispersed by topographic Rossby waves.