Linear and Nonliear Barotropic Decay on the Sphere

Isaac M. Held Geophysical Fluid Dynamics Laboratary/NOAA, Princeton, NJ 08542

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Peter J. Phillips Geophysical Fluid Dynamics Laboratary/NOAA, Princeton, NJ 08542

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Abstract

An example of the barotropic decay of wavelike midlatitude disturbance in the presence of a shear flow on the sphere is examined. The linear theory for the evolution of the disturbance is first described, with emphasis on the importance of the pseudomomentum spectrum for the resulting drag on the mean flow. After a brief discussion of the ways in which this linear theory can break down, a high-resolution nonlinear numerical model is used to examine the dependence of the mean-flow modification and the qualitative character of the decay on the amplitude of the initial disturbance.

Abstract

An example of the barotropic decay of wavelike midlatitude disturbance in the presence of a shear flow on the sphere is examined. The linear theory for the evolution of the disturbance is first described, with emphasis on the importance of the pseudomomentum spectrum for the resulting drag on the mean flow. After a brief discussion of the ways in which this linear theory can break down, a high-resolution nonlinear numerical model is used to examine the dependence of the mean-flow modification and the qualitative character of the decay on the amplitude of the initial disturbance.

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