A Nonhydrostatic Mesoscale Ocean Model. Part II: Numerical Implementation

Amala Mahadevan Department of Geophysical Sciences, University of Chicago, Chicago, Illinois

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Joseph Oliger Department of Computer Science, Stanford University, Stanford, California

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Robert Street Environmental Fluid Mechanics Laboratory, Stanford University, Stanford, California

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Abstract

The nonhydrostatic model with a free surface is numerically implemented in boundary-fitted curvilinear coordinates to model the mesoscale circulation in an ocean basin with natural topography. A semi-implicit numerical scheme is used, and the directional inhomogeneity in the elliptic equation for pressure is exploited to speed up the computation of its solution while using the multigrid method.

The model is used to simulate the circulation in the Gulf of Mexico. We observe the formation of the Loop Current and several eddies. The flow is very strongly controlled by the topography and our numerical experiments reveal that in the bottom layers, the flow along topographic contours is in the opposite direction of the anticyclonic circulation in the top layers.

Abstract

The nonhydrostatic model with a free surface is numerically implemented in boundary-fitted curvilinear coordinates to model the mesoscale circulation in an ocean basin with natural topography. A semi-implicit numerical scheme is used, and the directional inhomogeneity in the elliptic equation for pressure is exploited to speed up the computation of its solution while using the multigrid method.

The model is used to simulate the circulation in the Gulf of Mexico. We observe the formation of the Loop Current and several eddies. The flow is very strongly controlled by the topography and our numerical experiments reveal that in the bottom layers, the flow along topographic contours is in the opposite direction of the anticyclonic circulation in the top layers.

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