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\section{Example: Four layer Baroclinic Ocean Gyre In Spherical Coordinates} |
\section{Example: Four layer Baroclinic Ocean Gyre In Spherical Coordinates} |
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\label{sec:eg-fourlayer} |
\label{sect:eg-fourlayer} |
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\bodytext{bgcolor="#FFFFFFFF"} |
\bodytext{bgcolor="#FFFFFFFF"} |
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This document describes an example experiment using MITgcm |
This document describes an example experiment using MITgcm |
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to simulate a baroclinic ocean gyre in spherical |
to simulate a baroclinic ocean gyre in spherical |
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polar coordinates. The barotropic |
polar coordinates. The barotropic |
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example experiment in section \ref{sec:eg-baro} |
example experiment in section \ref{sect:eg-baro} |
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illustrated how to configure the code for a single layer |
illustrated how to configure the code for a single layer |
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simulation in a Cartesian grid. In this example a similar physical problem |
simulation in a Cartesian grid. In this example a similar physical problem |
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is simulated, but the code is now configured |
is simulated, but the code is now configured |
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Figure \ref{FIG:simulation_config} |
Figure \ref{FIG:simulation_config} |
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summarizes the configuration simulated. |
summarizes the configuration simulated. |
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In contrast to the example in section \ref{sec:eg-baro}, the |
In contrast to the example in section \ref{sect:eg-baro}, the |
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current experiment simulates a spherical polar domain. As indicated |
current experiment simulates a spherical polar domain. As indicated |
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by the axes in the lower left of the figure the model code works internally |
by the axes in the lower left of the figure the model code works internally |
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in a locally orthogonal coordinate $(x,y,z)$. For this experiment description |
in a locally orthogonal coordinate $(x,y,z)$. For this experiment description |
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\subsection{Equations solved} |
\subsection{Equations solved} |
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For this problem |
For this problem |
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the implicit free surface, {\bf HPE} (see section \ref{sec:hydrostatic_and_quasi-hydrostatic_forms}) form of the |
the implicit free surface, {\bf HPE} (see section \ref{sect:hydrostatic_and_quasi-hydrostatic_forms}) form of the |
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equations described in Marshall et. al \cite{Marshall97a} are |
equations described in Marshall et. al \cite{marshall:97a} are |
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employed. The flow is three-dimensional with just temperature, $\theta$, as |
employed. The flow is three-dimensional with just temperature, $\theta$, as |
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an active tracer. The equation of state is linear. |
an active tracer. The equation of state is linear. |
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A horizontal Laplacian operator $\nabla_{h}^2$ provides viscous |
A horizontal Laplacian operator $\nabla_{h}^2$ provides viscous |
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The procedure for generating a set of internal grid variables from a |
The procedure for generating a set of internal grid variables from a |
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spherical polar grid specification is discussed in section |
spherical polar grid specification is discussed in section |
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\ref{sec:spatial_discrete_horizontal_grid}. |
\ref{sect:spatial_discrete_horizontal_grid}. |
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\noindent\fbox{ \begin{minipage}{5.5in} |
\noindent\fbox{ \begin{minipage}{5.5in} |
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{\em S/R INI\_SPHERICAL\_POLAR\_GRID} ({\em |
{\em S/R INI\_SPHERICAL\_POLAR\_GRID} ({\em |
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As described in \ref{sec:tracer_equations}, the time evolution of potential |
As described in \ref{sect:tracer_equations}, the time evolution of potential |
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temperature, |
temperature, |
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$\theta$, (equation \ref{eq:eg_fourl_theta}) |
$\theta$, (equation \ref{eq:eg_fourl_theta}) |
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is evaluated prognostically. The centered second-order scheme with |
is evaluated prognostically. The centered second-order scheme with |
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Adams-Bashforth time stepping described in section |
Adams-Bashforth time stepping described in section |
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\ref{sec:tracer_equations_abII} is used to step forward the temperature |
\ref{sect:tracer_equations_abII} is used to step forward the temperature |
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equation. Prognostic terms in |
equation. Prognostic terms in |
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the momentum equations are solved using flux form as |
the momentum equations are solved using flux form as |
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described in section \ref{sec:flux-form_momentum_eqautions}. |
described in section \ref{sect:flux-form_momentum_eqautions}. |
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The pressure forces that drive the fluid motions, ( |
The pressure forces that drive the fluid motions, ( |
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$\frac{\partial p^{'}}{\partial \lambda}$ and $\frac{\partial p^{'}}{\partial \varphi}$), are found by summing pressure due to surface |
$\frac{\partial p^{'}}{\partial \lambda}$ and $\frac{\partial p^{'}}{\partial \varphi}$), are found by summing pressure due to surface |
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elevation $\eta$ and the hydrostatic pressure. The hydrostatic part of the |
elevation $\eta$ and the hydrostatic pressure. The hydrostatic part of the |
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height, $\eta$, is diagnosed using an implicit scheme. The pressure |
height, $\eta$, is diagnosed using an implicit scheme. The pressure |
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field solution method is described in sections |
field solution method is described in sections |
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\ref{sect:pressure-method-linear-backward} and |
\ref{sect:pressure-method-linear-backward} and |
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\ref{sec:finding_the_pressure_field}. |
\ref{sect:finding_the_pressure_field}. |
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\subsubsection{Numerical Stability Criteria} |
\subsubsection{Numerical Stability Criteria} |
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