Studies in Climate Dynamics for Environmental Security

A Note on the Lateral Eddy Viscosity Due to Transient Rossby Waves in a Barotropic Model

by W. Lawrence Gates

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Simulation of a wind-driven homogeneous ocean and its characteristic circulation. From time-dependent numerical solutions of the model, a negative lateral eddy viscosity is estimated in the basin interior, where flow is dominated by transient Rossby waves. These waves produce a systematic meridional convergence of eddy momentum into the latitudes of mean eastward current and are analogous to the Rossby waves in the general circulation of the atmosphere. This regime exists in spite of the formally prescribed lateral viscosity in the model's equations; the required viscous dissipation apparently occurs in the standing waves of the western boundary current system. Results suggest that a strong gradient of the effective eddy viscosity may be characteristic of an ocean with meridional boundaries. This investigation was begun as part of an effort to evaluate the effects of environmental perturbations that could be detrimental to the security and welfare of our nation. (See also RM-6110, RM-6211.)

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