On the Motion of Isolated Lenses on a Beta-Plane

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  • 1 Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, U.K. CB3 9EW.
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Abstract

This paper examines the motion and propagation of an isolated of anomalous water on a beta-plane, considered previously by Nof (1981). His perturbation analysis is extended to show the following:

1) Only westward propagation can occur, induced by the beta-effect; the eddy's speed must be ten less than two-thirds of the long Rossby-wave speed (unless the potential vorticity of the eddy is somewhere negative, which would be unlikely).

2) The eddy must be at least 2√2 deformation radii in radius.

3) The shape and velocity structure of the eddy has a simple structure, which is calculated for one range of cases.

4) The unperturbed eddy (on an f-plane) is stable to small disturbances making it likely that the eddy can propagate great distances before decaying.

Abstract

This paper examines the motion and propagation of an isolated of anomalous water on a beta-plane, considered previously by Nof (1981). His perturbation analysis is extended to show the following:

1) Only westward propagation can occur, induced by the beta-effect; the eddy's speed must be ten less than two-thirds of the long Rossby-wave speed (unless the potential vorticity of the eddy is somewhere negative, which would be unlikely).

2) The eddy must be at least 2√2 deformation radii in radius.

3) The shape and velocity structure of the eddy has a simple structure, which is calculated for one range of cases.

4) The unperturbed eddy (on an f-plane) is stable to small disturbances making it likely that the eddy can propagate great distances before decaying.

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