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- Title
Equatorial Circulation of a Global Ocean Climate Model with Anisotropic Horizontal Viscosity.
- Authors
Large, William G.; Danabasoglu, Gokhan; McWilliams, James C.; Gent, Peter R.; Bryan, Frank O.
- Abstract
ABSTRACT Horizontal momentum flux in a global ocean climate model is formulated as an anisotropic viscosity with two spatially varying coefficients. This friction can be made purely dissipative, does not produce unphysical torques, and satisfies the symmetry conditions required of the Reynolds stress tensor. The two primary design criteria are to have viscosity at values appropriate for the parameterization of missing mesoscale eddies wherever possible and to use other values only where required by the numerics. These other viscosities control numerical noise from advection and generate western boundary currents that are wide enough to be resolved by the coarse grid of the model. Noise on the model gridscale is tolerated provided its amplitude is less than about 0.05 cm s[sup -1]. Parameter tuning is minimized by applying physical and numerical principles. The potential value of this line of model development is demonstrated by comparison with equatorial ocean observations. In particular, the goal of producing model equatorial ocean currents comparable to observations was achieved in the Pacific Ocean. The Equatorial Undercurrent reaches a maximum magnitude of nearly 100 cms[sup -1] in the annual mean. Also, the spatial distribution of near-surface currents compares favorably with observations from the Global Drifter Program. The exceptions are off the equator; in the model the North Equatorial Countercurrent is improved, but still too weak, and the northward flow along the coast of South America may be too shallow. Equatorial Pacific upwelling has a realistic...
- Subjects
OCEAN; EDDY flux; REYNOLDS stress
- Publication
Journal of Physical Oceanography, 2001, Vol 31, Issue 2, p518
- ISSN
0022-3670
- Publication type
Article
- DOI
10.1175/1520-0485(2001)031<0518:ECOAGO>2.0.CO;2