Yves Morel

The Interaction of a Vortex with a Stable Jet

We examine the nonlinear interactions between a zonal jet and a vortex (oceanic eddy), using a one-and-a-half-layer quasi-geostrophic numerical model. The eastward jet is defined by two strips of constant and opposite potential vorticity; it is stable in isolation. The anticyclonic eddy is initialized north of the jet by a circular patch of constant potential vorticity. We numerically determine the physical conditions under which the eddy crosses the jet meridionally, or drifts along its northern side. Three groups of dynamic regimes are found: the first one with the eddy staying north of the jet and drifting eastward, the second one with the eddy crossing the jet and then drifting away as a dipole, and the last one with the eddy also crossing the jet, and progressing eastward. Furthermore, an analytical criterion for the crossing of the jet is established, which remarkably compares with the numerical experiments. The sensitivity of these dynamic regimes to environmental parameters is finally examined.