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3.10.2 Equations solved

For this problem the implicit free surface, HPE (see section 1.3.4.2) form of the equations described in Marshall et. al Marshall et al. [1997b] are employed. The flow is three-dimensional with just temperature, $ \theta $ , as an active tracer. The equation of state is linear. A horizontal Laplacian operator $ \nabla_{h}^2$ provides viscous dissipation and provides a diffusive sub-grid scale closure for the temperature equation. A wind-stress momentum forcing is added to the momentum equation for the zonal flow, $ u$ . Other terms in the model are explicitly switched off for this experiment configuration (see section 3.10.4 ). This yields an active set of equations solved in this configuration, written in spherical polar coordinates as follows


$\displaystyle \frac{Du}{Dt} - fv +
\frac{1}{\rho}\frac{\partial p^{\prime}}{\...
...ial \lambda} -
A_{h}\nabla_{h}^2u - A_{z}\frac{\partial^{2}u}{\partial z^{2}}$ $\displaystyle =$ $\displaystyle \cal{F}_{\lambda}$ (3.14)
$\displaystyle \frac{Dv}{Dt} + fu +
\frac{1}{\rho}\frac{\partial p^{\prime}}{\...
...ial \varphi} -
A_{h}\nabla_{h}^2v - A_{z}\frac{\partial^{2}v}{\partial z^{2}}$ $\displaystyle =$ 0 (3.15)
$\displaystyle \frac{\partial \eta}{\partial t} + \frac{\partial H \widehat{u}}{\partial \lambda} +
\frac{\partial H \widehat{v}}{\partial \varphi}$ $\displaystyle =$ 0 (3.16)
$\displaystyle \frac{D\theta}{Dt} -
K_{h}\nabla_{h}^2\theta - K_{z}\frac{\partial^{2}\theta}{\partial z^{2}}$ $\displaystyle =$ 0 (3.17)
$\displaystyle p^{\prime}$ $\displaystyle =$ $\displaystyle g\rho_{0} \eta + \int^{0}_{-z}\rho^{\prime} dz$ (3.18)
$\displaystyle \rho ^{\prime }$ $\displaystyle =$ $\displaystyle - \alpha_{\theta}\rho_{0}\theta^{\prime}$ (3.19)
$\displaystyle {\cal F}_{\lambda} \vert _{s}$ $\displaystyle =$ $\displaystyle \frac{\tau_{\lambda}}{\rho_{0}\Delta z_{s}}$ (3.20)
$\displaystyle {\cal F}_{\lambda} \vert _{i}$ $\displaystyle =$ 0 (3.21)

where $ u$ and $ v$ are the components of the horizontal flow vector $ \vec{u}$ on the sphere ( $ u=\dot{\lambda},v=\dot{\varphi}$ ). The terms $ H\widehat{u}$ and $ H\widehat{v}$ are the components of the vertical integral term given in equation 1.35 and explained in more detail in section 2.4. However, for the problem presented here, the continuity relation (equation 3.16) differs from the general form given in section 2.4, equation 2.15, because the source terms $ {\cal P}-{\cal E}+{\cal R}$ are all 0 .

The pressure field, $ p^{\prime }$ , is separated into a barotropic part due to variations in sea-surface height, $ \eta $ , and a hydrostatic part due to variations in density, $ \rho ^{\prime }$ , integrated through the water column.

The suffices $ {s},{i}$ indicate surface layer and the interior of the domain. The windstress forcing, $ {\cal F}_{\lambda}$ , is applied in the surface layer by a source term in the zonal momentum equation. In the ocean interior this term is zero.

In the momentum equations lateral and vertical boundary conditions for the $ \nabla_{h}^{2}$ and $ \frac{\partial^{2}}{\partial z^{2}}$ operators are specified when the numerical simulation is run - see section 3.10.4. For temperature the boundary condition is ``zero-flux'' e.g. $ \frac{\partial \theta}{\partial \varphi}=
\frac{\partial \theta}{\partial \lambda}=\frac{\partial \theta}{\partial z}=0$ .


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Next: 3.10.3 Discrete Numerical Configuration Up: 3.10 Baroclinic Gyre MITgcm Previous: 3.10.1 Overview   Contents
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