The Interaction of an Eddy with an Unstable Jet

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Abstract
Interactions between an unstable jet and eddy are explored using a jet with piecewise constant potential vorticity. A linear theory is developed for the case where the jet is nearly zonal and the eddy is far away in the sense that the eddy may be replaced by a point vortex that induces velocity perturbations in the jet small compared with the maximum jet velocity. The calculations are extended into the nonlinear domain by the method of contour dynamics. Specific examples of barotropic and equivalent barotropic jets are discussed, with particular attention to processes leading to eddy propagation. In the barotropic case, long-range eddy-jet interactions are dominated by the jet instability, which breaks the jet up into eddies downstream from the forcing eddy. For a forcing eddy south of an unperturbed eastward flowing jet, the initial eddy propagation tendency is southwestward (SW) for cyclones and northeastward (NE) for anticyclones. In the equivalent barotropic case, the fact that long waves in ... Abstract Interactions between an unstable jet and eddy are explored using a jet with piecewise constant potential vorticity. A linear theory is developed for the case where the jet is nearly zonal and the eddy is far away in the sense that the eddy may be replaced by a point vortex that induces velocity perturbations in the jet small compared with the maximum jet velocity. The calculations are extended into the nonlinear domain by the method of contour dynamics. Specific examples of barotropic and equivalent barotropic jets are discussed, with particular attention to processes leading to eddy propagation. In the barotropic case, long-range eddy-jet interactions are dominated by the jet instability, which breaks the jet up into eddies downstream from the forcing eddy. For a forcing eddy south of an unperturbed eastward flowing jet, the initial eddy propagation tendency is southwestward (SW) for cyclones and northeastward (NE) for anticyclones. In the equivalent barotropic case, the fact that long waves in ...

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