Chapter 3
MODELS OF THE OCEAN:
WHICH OCEAN?
Anne Marie Treguier
CNRS, LPO, Plouzan6, France
Abstract
Physics actually represented in an ocean model depend on each model's
resolution and its parameterization of subgridscale effects. This chapter is a review of parameterizations used in ocean models, focussing
on operational ocean forecasting systems for the North Atlantic and
Mediterranean Sea. This review is limited to zicoordinate models. A
detailed presentation of the physics underlying each parameterization is
out of the scope of this short chapter, but we try to discuss some uncertainties of the physical basis of current parameterizations. The concept
of subgrid scale effects and some interesting properties of the diffusion equation are presented first. Because ocean turbulence is strongly
anisotropic, parameterization in the vertical and horizontal (or isopycnal) directions differ and are presented separately. Special sections are
devoted to bottom boundary layers, flow topography interactions, and
the dynamical effects of mesoscale eddies.
Keywords: Parameterizations, ocean modelling, numerical models, subgrid scale
physics, diffusion, viscosity.
A simplistic view of the surface ocean circulation is often found in
geographical maps, with arrows displaying the direction and location
of the main surface currents. Those are the large scale, wind driven
currents which Sverdrup and Stommel, among others pioneers, have tried
to understand. The first models of the wind-forced ocean circulation that
they built were two-dimensional, used the simplified quasi-geostrophic
equations, and the western boundary currents were viscous boundary
layers.
This linear, viscous ocean is still what is represented in most climate
models today. The sea surface height distribution in the South Atlantic
75
E. P. Chassignet and J. Verron (eds.), Ocean Weather Forecasting, 75-108.
O 2006 Springer. Printed in the Netherlands.
MODELS OF THE OCEAN:
WHICH OCEAN?
Anne Marie Treguier
CNRS, LPO, Plouzan6, France
Abstract
Physics actually represented in an ocean model depend on each model's
resolution and its parameterization of subgridscale effects. This chapter is a review of parameterizations used in ocean models, focussing
on operational ocean forecasting systems for the North Atlantic and
Mediterranean Sea. This review is limited to zicoordinate models. A
detailed presentation of the physics underlying each parameterization is
out of the scope of this short chapter, but we try to discuss some uncertainties of the physical basis of current parameterizations. The concept
of subgrid scale effects and some interesting properties of the diffusion equation are presented first. Because ocean turbulence is strongly
anisotropic, parameterization in the vertical and horizontal (or isopycnal) directions differ and are presented separately. Special sections are
devoted to bottom boundary layers, flow topography interactions, and
the dynamical effects of mesoscale eddies.
Keywords: Parameterizations, ocean modelling, numerical models, subgrid scale
physics, diffusion, viscosity.
A simplistic view of the surface ocean circulation is often found in
geographical maps, with arrows displaying the direction and location
of the main surface currents. Those are the large scale, wind driven
currents which Sverdrup and Stommel, among others pioneers, have tried
to understand. The first models of the wind-forced ocean circulation that
they built were two-dimensional, used the simplified quasi-geostrophic
equations, and the western boundary currents were viscous boundary
layers.
This linear, viscous ocean is still what is represented in most climate
models today. The sea surface height distribution in the South Atlantic
75
E. P. Chassignet and J. Verron (eds.), Ocean Weather Forecasting, 75-108.
O 2006 Springer. Printed in the Netherlands.