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\section{Example: Barotropic Ocean Gyre In Cartesian Coordinates} |
\section{Example: Barotropic Ocean Gyre In Cartesian Coordinates} |
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\label{sec:eg-baro} |
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\bodytext{bgcolor="#FFFFFFFF"} |
\bodytext{bgcolor="#FFFFFFFF"} |
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%{\large May 2001} |
%{\large May 2001} |
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%\end{center} |
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\subsection{Introduction} |
This is the first in a series of sections describing |
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This document is the first in a series of documents describing |
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example MITgcm numerical experiments. The example experiments |
example MITgcm numerical experiments. The example experiments |
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include both straightforward examples of idealised geophysical |
include both straightforward examples of idealised geophysical |
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fluid simulations and more involved cases encompassing |
fluid simulations and more involved cases encompassing |
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large scale modeling and |
large scale modeling and |
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automatic differentiation. Both hydrostatic and non-hydrostatic |
automatic differentiation. Both hydrostatic and non-hydrostatic |
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experiements are presented, as well as experiments employing |
experiments are presented, as well as experiments employing |
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cartesian, spherical-polar and cube-sphere coordinate systems. |
cartesian, spherical-polar and cube-sphere coordinate systems. |
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These ``case study'' documents include information describing |
These ``case study'' documents include information describing |
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the experimental configuration and detailed information on how to |
the experimental configuration and detailed information on how to |
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summarises the configuration simulated. |
summarises the configuration simulated. |
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\begin{figure} |
\begin{figure} |
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\centerline{ |
\begin{center} |
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\resizebox{7.5in}{5.5in}{ |
\resizebox{7.5in}{5.5in}{ |
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\includegraphics*[0.2in,0.7in][10.5in,10.5in] |
\includegraphics*[0.2in,0.7in][10.5in,10.5in] |
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{part3/case_studies/barotropic_gyre/simulation_config.eps} } |
{part3/case_studies/barotropic_gyre/simulation_config.eps} } |
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} |
\end{center} |
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\caption{Schematic of simulation domain and wind-stress forcing function |
\caption{Schematic of simulation domain and wind-stress forcing function |
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for barotropic gyre numerical experiment. The domain is enclosed bu solid |
for barotropic gyre numerical experiment. The domain is enclosed bu solid |
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walls at $x=$~0,1200km and at $y=$~0,1200km.} |
walls at $x=$~0,1200km and at $y=$~0,1200km.} |
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\label{FIG:simulation_config} |
\label{FIG:simulation_config} |
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\end{figure} |
\end{figure} |
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\subsection{Discrete Numerical Configuration} |
\subsection{Equations Solved} |
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The model is configured in hydrostatic form. The implicit free surface form of the |
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The model is configured in hydrostatic form. The domain is discretised with |
pressure equation described in Marshall et. al \cite{Marshall97a} is |
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a uniform grid spacing in the horizontal set to |
employed. |
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$\Delta x=\Delta y=20$~km, so |
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that there are sixty grid cells in the $x$ and $y$ directions. Vertically the |
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model is configured with a single layer with depth, $\Delta z$, of $5000$~m. |
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The implicit free surface form of the |
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pressure equation described in Marshall et. al \cite{Marshall97a} is |
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employed. |
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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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dissipation. The wind-stress momentum input is added to the momentum equation |
dissipation. The wind-stress momentum input is added to the momentum equation |
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for the ``zonal flow'', $u$. Other terms in the model |
for the ``zonal flow'', $u$. Other terms in the model |
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are explicitly switched off for this experiement configuration (see section |
are explicitly switched off for this experiement configuration (see section |
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\ref{SEC:code_config} ), yielding an active set of equations solved in this |
\ref{SEC:code_config} ), yielding an active set of equations solved in this |
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configuration as follows |
configuration as follows |
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\begin{eqnarray} |
\begin{eqnarray} |
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\label{EQ:model_equations} |
\label{EQ:model_equations} |
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\frac{Du}{Dt} - fv + |
\frac{Du}{Dt} - fv + |
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g\frac{\partial \eta}{\partial x} - |
g\frac{\partial \eta}{\partial x} - |
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A_{h}\nabla_{h}^2u |
A_{h}\nabla_{h}^2u |
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& = & |
& = & |
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\frac{\tau_{x}}{\rho_{0}\Delta z} |
\frac{\tau_{x}}{\rho_{0}\Delta z} |
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\\ |
\\ |
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\frac{Dv}{Dt} + fu + g\frac{\partial \eta}{\partial y} - |
\frac{Dv}{Dt} + fu + g\frac{\partial \eta}{\partial y} - |
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A_{h}\nabla_{h}^2v |
A_{h}\nabla_{h}^2v |
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& = & |
& = & |
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0 |
0 |
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\\ |
\\ |
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\end{eqnarray} |
\end{eqnarray} |
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\noindent where $u$ and $v$ and the $x$ and $y$ components of the |
\noindent where $u$ and $v$ and the $x$ and $y$ components of the |
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flow vector $\vec{u}$. |
flow vector $\vec{u}$. |
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\\ |
\\ |
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\subsection{Discrete Numerical Configuration} |
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The domain is discretised with |
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a uniform grid spacing in the horizontal set to |
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$\Delta x=\Delta y=20$~km, so |
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that there are sixty grid cells in the $x$ and $y$ directions. Vertically the |
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model is configured with a single layer with depth, $\Delta z$, of $5000$~m. |
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\subsubsection{Numerical Stability Criteria} |
\subsubsection{Numerical Stability Criteria} |
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The laplacian dissipation coefficient, $A_{h}$, is set to $400 m s^{-1}$. |
The laplacian dissipation coefficient, $A_{h}$, is set to $400 m s^{-1}$. |