s_examples/barotropic_gyre/baro.tex

% $Header: /u/u0/gcmpack/mitgcmdoc/part3/case_studies/barotropic_gyre/baro.tex,v 1.2 2001/09/27 00:58:17 cnh Exp $
% $Name:  $

\section{Example: Barotropic Ocean Gyre In Cartesian Coordinates}
\label{sec:eg-baro}

\bodytext{bgcolor="#FFFFFFFF"}

%\begin{center} 
%{\Large \bf Using MITgcm to Simulate a Barotropic Ocean Gyre In Cartesian
%Coordinates}
%
%\vspace*{4mm}
%
%\vspace*{3mm}
%{\large May 2001}
%\end{center}

This is the first in a series of sections describing
example MITgcm numerical experiments. The example experiments 
include both straightforward examples of idealised geophysical 
fluid simulations and more involved cases encompassing
large scale modeling and
automatic differentiation. Both hydrostatic and non-hydrostatic 
experiments are presented, as well as experiments employing
cartesian, spherical-polar and cube-sphere coordinate systems.
These ``case study'' documents include information describing
the experimental configuration and detailed information on how to
configure the MITgcm code and input files for each experiment.

\subsection{Experiment Overview}

This example experiment demonstrates using the MITgcm to simulate
a barotropic, wind-forced, ocean gyre circulation. The experiment 
is a numerical rendition of the gyre circulation problem simliar
to the problems described analytically by Stommel in 1966 
\cite{Stommel66} and numerically in Holland et. al \cite{Holland75}.

In this experiment the model 
is configured to represent a rectangular enclosed box of fluid,
$1200 \times 1200 $~km in lateral extent. The fluid is $5$~km deep and is forced
by a constant in time zonal wind stress, $\tau_x$, that varies sinusoidally
in the ``north-south'' direction. Topologically the grid is cartesian and 
the coriolis parameter $f$ is defined according to a mid-latitude beta-plane 
equation

\begin{equation}
\label{EQ:fcori}
f(y) = f_{0}+\beta y
\end{equation}
 
\noindent where $y$ is the distance along the ``north-south'' axis of the 
simulated domain. For this experiment $f_{0}$ is set to $10^{-4}s^{-1}$ in 
(\ref{EQ:fcori}) and $\beta = 10^{-11}s^{-1}m^{-1}$. 
\\
\\
 The sinusoidal wind-stress variations are defined according to 

\begin{equation}
\label{EQ:taux}
\tau_x(y) = \tau_{0}\sin(\pi \frac{y}{L_y})
\end{equation}
 
\noindent where $L_{y}$ is the lateral domain extent ($1200$~km) and 
$\tau_0$ is set to $0.1N m^{-2}$. 
\\
\\
Figure \ref{FIG:simulation_config}
summarises the configuration simulated.

\begin{figure}
\begin{center}
 \resizebox{7.5in}{5.5in}{
   \includegraphics*[0.2in,0.7in][10.5in,10.5in]
    {part3/case_studies/barotropic_gyre/simulation_config.eps} }
\end{center}
\caption{Schematic of simulation domain and wind-stress forcing function 
for barotropic gyre numerical experiment. The domain is enclosed bu solid
walls at $x=$~0,1200km and at $y=$~0,1200km.}
\label{FIG:simulation_config}
\end{figure}

\subsection{Equations Solved}
The model is configured in hydrostatic form. The implicit free surface form of the
pressure equation described in Marshall et. al \cite{Marshall97a} is
employed.
A horizontal laplacian operator $\nabla_{h}^2$ provides viscous
dissipation. The wind-stress momentum input is added to the momentum equation
for the ``zonal flow'', $u$. Other terms in the model
are explicitly switched off for this experiement configuration (see section
\ref{SEC:code_config} ), yielding an active set of equations solved in this
configuration as follows 

\begin{eqnarray}
\label{EQ:model_equations}
\frac{Du}{Dt} - fv +
              g\frac{\partial \eta}{\partial x} -
              A_{h}\nabla_{h}^2u
& = &
\frac{\tau_{x}}{\rho_{0}\Delta z}
\\
\frac{Dv}{Dt} + fu + g\frac{\partial \eta}{\partial y} -
              A_{h}\nabla_{h}^2v
& = &
0
\\
\frac{\partial \eta}{\partial t} + \nabla_{h}\cdot \vec{u}
&=&
0
\end{eqnarray}

\noindent where $u$ and $v$ and the $x$ and $y$ components of the
flow vector $\vec{u}$.
\\


\subsection{Discrete Numerical Configuration}

 The domain is discretised with 
a uniform grid spacing in the horizontal set to
 $\Delta x=\Delta y=20$~km, so 
that there are sixty grid cells in the $x$ and $y$ directions. Vertically the 
model is configured with a single layer with depth, $\Delta z$, of $5000$~m. 

\subsubsection{Numerical Stability Criteria}

The laplacian dissipation coefficient, $A_{h}$, is set to $400 m s^{-1}$.
This value is chosen to yield a Munk layer width \cite{Adcroft_thesis},

\begin{eqnarray}
\label{EQ:munk_layer}
M_{w} = \pi ( \frac { A_{h} }{ \beta } )^{\frac{1}{3}}
\end{eqnarray}

\noindent  of $\approx 100$km. This is greater than the model
resolution $\Delta x$, ensuring that the frictional boundary
layer is well resolved.
\\

\noindent The model is stepped forward with a 
time step $\delta t=1200$secs. With this time step the stability 
parameter to the horizontal laplacian friction \cite{Adcroft_thesis}


\begin{eqnarray}
\label{EQ:laplacian_stability}
S_{l} = 4 \frac{A_{h} \delta t}{{\Delta x}^2}
\end{eqnarray}

\noindent evaluates to 0.012, which is well below the 0.3 upper limit
for stability. 
\\

\noindent The numerical stability for inertial oscillations  
\cite{Adcroft_thesis} 

\begin{eqnarray}
\label{EQ:inertial_stability}
S_{i} = f^{2} {\delta t}^2
\end{eqnarray}

\noindent evaluates to $0.0144$, which is well below the $0.5$ upper 
limit for stability.
\\

\noindent The advective CFL \cite{Adcroft_thesis} for an extreme maximum 
horizontal flow speed of $ | \vec{u} | = 2 ms^{-1}$

\begin{eqnarray}
\label{EQ:cfl_stability}
S_{a} = \frac{| \vec{u} | \delta t}{ \Delta x}
\end{eqnarray}

\noindent evaluates to 0.12. This is approaching the stability limit
of 0.5 and limits $\delta t$ to $1200s$.

\subsection{Code Configuration}
\label{SEC:code_config}

The model configuration for this experiment resides under the 
directory {\it verification/exp0/}.  The experiment files 
\begin{itemize}
\item {\it input/data}
\item {\it input/data.pkg}
\item {\it input/eedata},
\item {\it input/windx.sin\_y},
\item {\it input/topog.box},
\item {\it code/CPP\_EEOPTIONS.h}
\item {\it code/CPP\_OPTIONS.h},
\item {\it code/SIZE.h}. 
\end{itemize}
contain the code customisations and parameter settings for this 
experiements. Below we describe the customisations
to these files associated with this experiment.

\subsubsection{File {\it input/data}}

This file, reproduced completely below, specifies the main parameters 
for the experiment. The parameters that are significant for this configuration
are

\begin{itemize}

\item Line 7, \begin{verbatim} viscAh=4.E2, \end{verbatim} this line sets
the laplacian friction coefficient to $400 m^2s^{-1}$
\item Line 10, \begin{verbatim} beta=1.E-11, \end{verbatim} this line sets
$\beta$ (the gradient of the coriolis parameter, $f$) to $10^{-11} s^{-1}m^{-1}$

\item Lines 15 and 16
\begin{verbatim}
rigidLid=.FALSE.,
implicitFreeSurface=.TRUE.,
\end{verbatim}
these lines suppress the rigid lid formulation of the surface
pressure inverter and activate the implicit free surface form
of the pressure inverter.

\item Line 27,
\begin{verbatim}
startTime=0,
\end{verbatim}
this line indicates that the experiment should start from $t=0$
and implicitly supresses searching for checkpoint files associated
with restarting an numerical integration from a previously saved state.

\item Line 29,
\begin{verbatim}
endTime=12000,
\end{verbatim}
this line indicates that the experiment should start finish at $t=12000s$.
A restart file will be written at this time that will enable the
simulation to be continued from this point.

\item Line 30,
\begin{verbatim}
deltaTmom=1200,
\end{verbatim}
This line sets the momentum equation timestep to $1200s$.

\item Line 39,
\begin{verbatim}
usingCartesianGrid=.TRUE.,
\end{verbatim}
This line requests that the simulation be performed in a 
cartesian coordinate system.

\item Line 41,
\begin{verbatim}
delX=60*20E3,
\end{verbatim}
This line sets the horizontal grid spacing between each x-coordinate line
in the discrete grid. The syntax indicates that the discrete grid
should be comprise of $60$ grid lines each separated by $20 \times 10^{3}m$
($20$~km).

\item Line 42,
\begin{verbatim}
delY=60*20E3,
\end{verbatim}
This line sets the horizontal grid spacing between each y-coordinate line
in the discrete grid to $20 \times 10^{3}m$ ($20$~km).

\item Line 43,
\begin{verbatim}
delZ=5000,
\end{verbatim}
This line sets the vertical grid spacing between each z-coordinate line
in the discrete grid to $5000m$ ($5$~km).

\item Line 46,
\begin{verbatim}
bathyFile='topog.box'
\end{verbatim}
This line specifies the name of the file from which the domain
bathymetry is read. This file is a two-dimensional ($x,y$) map of
depths. This file is assumed to contain 64-bit binary numbers 
giving the depth of the model at each grid cell, ordered with the x 
coordinate varying fastest. The points are ordered from low coordinate
to high coordinate for both axes. The units and orientation of the
depths in this file are the same as used in the MITgcm code. In this
experiment, a depth of $0m$ indicates a solid wall and a depth
of $-5000m$ indicates open ocean. The matlab program
{\it input/gendata.m} shows an example of how to generate a
bathymetry file.


\item Line 49,
\begin{verbatim}
zonalWindFile='windx.sin_y'
\end{verbatim}
This line specifies the name of the file from which the x-direction
surface wind stress is read. This file is also a two-dimensional
($x,y$) map and is enumerated and formatted in the same manner as the 
bathymetry file. The matlab program {\it input/gendata.m} includes example 
code to generate a valid {\bf zonalWindFile} file.  

\end{itemize}

\noindent other lines in the file {\it input/data} are standard values
that are described in the MITgcm Getting Started and MITgcm Parameters
notes.

\begin{small}
\input{part3/case_studies/barotropic_gyre/input/data}
\end{small}

\subsubsection{File {\it input/data.pkg}}

This file uses standard default values and does not contain
customisations for this experiment.

\subsubsection{File {\it input/eedata}}

This file uses standard default values and does not contain
customisations for this experiment.

\subsubsection{File {\it input/windx.sin\_y}}

The {\it input/windx.sin\_y} file specifies a two-dimensional ($x,y$) 
map of wind stress ,$\tau_{x}$, values. The units used are $Nm^{-2}$.
Although $\tau_{x}$ is only a function of $y$n in this experiment
this file must still define a complete two-dimensional map in order
to be compatible with the standard code for loading forcing fields 
in MITgcm. The included matlab program {\it input/gendata.m} gives a complete
code for creating the {\it input/windx.sin\_y} file.

\subsubsection{File {\it input/topog.box}}


The {\it input/topog.box} file specifies a two-dimensional ($x,y$) 
map of depth values. For this experiment values are either
$0m$ or {\bf -delZ}m, corresponding respectively to a wall or to deep
ocean. The file contains a raw binary stream of data that is enumerated
in the same way as standard MITgcm two-dimensional, horizontal arrays.
The included matlab program {\it input/gendata.m} gives a complete
code for creating the {\it input/topog.box} file.

\subsubsection{File {\it code/SIZE.h}}

Two lines are customized in this file for the current experiment

\begin{itemize}

\item Line 39, 
\begin{verbatim} sNx=60, \end{verbatim} this line sets
the lateral domain extent in grid points for the
axis aligned with the x-coordinate.

\item Line 40, 
\begin{verbatim} sNy=60, \end{verbatim} this line sets
the lateral domain extent in grid points for the
axis aligned with the y-coordinate.

\end{itemize}

\begin{small}
\input{part3/case_studies/barotropic_gyre/code/SIZE.h}
\end{small}

\subsubsection{File {\it code/CPP\_OPTIONS.h}}

This file uses standard default values and does not contain
customisations for this experiment.


\subsubsection{File {\it code/CPP\_EEOPTIONS.h}}

This file uses standard default values and does not contain
customisations for this experiment.

1	cnh	1.3	% $Header: /u/u0/gcmpack/mitgcmdoc/part3/case_studies/barotropic_gyre/baro.tex,v 1.2 2001/09/27 00:58:17 cnh Exp $
2	cnh	1.2	% $Name: $
3	adcroft	1.1
4			\section{Example: Barotropic Ocean Gyre In Cartesian Coordinates}
5	cnh	1.3	\label{sec:eg-baro}
6	adcroft	1.1
7			\bodytext{bgcolor="#FFFFFFFF"}
8
9			%\begin{center}
10			%{\Large \bf Using MITgcm to Simulate a Barotropic Ocean Gyre In Cartesian
11			%Coordinates}
12			%
13			%\vspace*{4mm}
14			%
15			%\vspace*{3mm}
16			%{\large May 2001}
17			%\end{center}
18
19	cnh	1.3	This is the first in a series of sections describing
20	adcroft	1.1	example MITgcm numerical experiments. The example experiments
21			include both straightforward examples of idealised geophysical
22			fluid simulations and more involved cases encompassing
23			large scale modeling and
24			automatic differentiation. Both hydrostatic and non-hydrostatic
25	cnh	1.3	experiments are presented, as well as experiments employing
26	adcroft	1.1	cartesian, spherical-polar and cube-sphere coordinate systems.
27			These ``case study'' documents include information describing
28			the experimental configuration and detailed information on how to
29			configure the MITgcm code and input files for each experiment.
30
31			\subsection{Experiment Overview}
32
33			This example experiment demonstrates using the MITgcm to simulate
34			a barotropic, wind-forced, ocean gyre circulation. The experiment
35			is a numerical rendition of the gyre circulation problem simliar
36			to the problems described analytically by Stommel in 1966
37			\cite{Stommel66} and numerically in Holland et. al \cite{Holland75}.
38
39			In this experiment the model
40			is configured to represent a rectangular enclosed box of fluid,
41			$1200 \times 1200 $~km in lateral extent. The fluid is $5$~km deep and is forced
42			by a constant in time zonal wind stress, $\tau_x$, that varies sinusoidally
43			in the ``north-south'' direction. Topologically the grid is cartesian and
44			the coriolis parameter $f$ is defined according to a mid-latitude beta-plane
45			equation
46
47			\begin{equation}
48			\label{EQ:fcori}
49			f(y) = f_{0}+\beta y
50			\end{equation}
51
52			\noindent where $y$ is the distance along the ``north-south'' axis of the
53			simulated domain. For this experiment $f_{0}$ is set to $10^{-4}s^{-1}$ in
54			(\ref{EQ:fcori}) and $\beta = 10^{-11}s^{-1}m^{-1}$.
55			\\
56			\\
57			The sinusoidal wind-stress variations are defined according to
58
59			\begin{equation}
60			\label{EQ:taux}
61			\tau_x(y) = \tau_{0}\sin(\pi \frac{y}{L_y})
62			\end{equation}
63
64			\noindent where $L_{y}$ is the lateral domain extent ($1200$~km) and
65			$\tau_0$ is set to $0.1N m^{-2}$.
66			\\
67			\\
68			Figure \ref{FIG:simulation_config}
69			summarises the configuration simulated.
70
71			\begin{figure}
72	cnh	1.2	\begin{center}
73	adcroft	1.1	\resizebox{7.5in}{5.5in}{
74			\includegraphics*[0.2in,0.7in][10.5in,10.5in]
75			{part3/case_studies/barotropic_gyre/simulation_config.eps} }
76	cnh	1.2	\end{center}
77	adcroft	1.1	\caption{Schematic of simulation domain and wind-stress forcing function
78			for barotropic gyre numerical experiment. The domain is enclosed bu solid
79			walls at $x=$~0,1200km and at $y=$~0,1200km.}
80			\label{FIG:simulation_config}
81			\end{figure}
82
83	cnh	1.3	\subsection{Equations Solved}
84			The model is configured in hydrostatic form. The implicit free surface form of the
85			pressure equation described in Marshall et. al \cite{Marshall97a} is
86			employed.
87	adcroft	1.1	A horizontal laplacian operator $\nabla_{h}^2$ provides viscous
88			dissipation. The wind-stress momentum input is added to the momentum equation
89			for the ``zonal flow'', $u$. Other terms in the model
90			are explicitly switched off for this experiement configuration (see section
91	cnh	1.3	\ref{SEC:code_config} ), yielding an active set of equations solved in this
92			configuration as follows
93	adcroft	1.1
94			\begin{eqnarray}
95			\label{EQ:model_equations}
96	cnh	1.3	\frac{Du}{Dt} - fv +
97			g\frac{\partial \eta}{\partial x} -
98			A_{h}\nabla_{h}^2u
99	adcroft	1.1	& = &
100			\frac{\tau_{x}}{\rho_{0}\Delta z}
101			\\
102			\frac{Dv}{Dt} + fu + g\frac{\partial \eta}{\partial y} -
103	cnh	1.3	A_{h}\nabla_{h}^2v
104	adcroft	1.1	& = &
105			0
106			\\
107			\frac{\partial \eta}{\partial t} + \nabla_{h}\cdot \vec{u}
108			&=&
109			0
110			\end{eqnarray}
111
112			\noindent where $u$ and $v$ and the $x$ and $y$ components of the
113	cnh	1.3	flow vector $\vec{u}$.
114	adcroft	1.1	\\
115	cnh	1.3
116
117			\subsection{Discrete Numerical Configuration}
118
119			The domain is discretised with
120			a uniform grid spacing in the horizontal set to
121			$\Delta x=\Delta y=20$~km, so
122			that there are sixty grid cells in the $x$ and $y$ directions. Vertically the
123			model is configured with a single layer with depth, $\Delta z$, of $5000$~m.
124	adcroft	1.1
125			\subsubsection{Numerical Stability Criteria}
126
127			The laplacian dissipation coefficient, $A_{h}$, is set to $400 m s^{-1}$.
128			This value is chosen to yield a Munk layer width \cite{Adcroft_thesis},
129
130			\begin{eqnarray}
131			\label{EQ:munk_layer}
132			M_{w} = \pi ( \frac { A_{h} }{ \beta } )^{\frac{1}{3}}
133			\end{eqnarray}
134
135			\noindent of $\approx 100$km. This is greater than the model
136			resolution $\Delta x$, ensuring that the frictional boundary
137			layer is well resolved.
138			\\
139
140			\noindent The model is stepped forward with a
141			time step $\delta t=1200$secs. With this time step the stability
142			parameter to the horizontal laplacian friction \cite{Adcroft_thesis}
143
144
145
146			\begin{eqnarray}
147			\label{EQ:laplacian_stability}
148			S_{l} = 4 \frac{A_{h} \delta t}{{\Delta x}^2}
149			\end{eqnarray}
150
151			\noindent evaluates to 0.012, which is well below the 0.3 upper limit
152			for stability.
153			\\
154
155			\noindent The numerical stability for inertial oscillations
156			\cite{Adcroft_thesis}
157
158			\begin{eqnarray}
159			\label{EQ:inertial_stability}
160			S_{i} = f^{2} {\delta t}^2
161			\end{eqnarray}
162
163			\noindent evaluates to $0.0144$, which is well below the $0.5$ upper
164			limit for stability.
165			\\
166
167			\noindent The advective CFL \cite{Adcroft_thesis} for an extreme maximum
168			horizontal flow speed of $ \| \vec{u} \| = 2 ms^{-1}$
169
170			\begin{eqnarray}
171			\label{EQ:cfl_stability}
172			S_{a} = \frac{\| \vec{u} \| \delta t}{ \Delta x}
173			\end{eqnarray}
174
175			\noindent evaluates to 0.12. This is approaching the stability limit
176			of 0.5 and limits $\delta t$ to $1200s$.
177
178			\subsection{Code Configuration}
179			\label{SEC:code_config}
180
181			The model configuration for this experiment resides under the
182			directory {\it verification/exp0/}. The experiment files
183			\begin{itemize}
184			\item {\it input/data}
185			\item {\it input/data.pkg}
186			\item {\it input/eedata},
187			\item {\it input/windx.sin\_y},
188			\item {\it input/topog.box},
189			\item {\it code/CPP\_EEOPTIONS.h}
190			\item {\it code/CPP\_OPTIONS.h},
191			\item {\it code/SIZE.h}.
192			\end{itemize}
193			contain the code customisations and parameter settings for this
194			experiements. Below we describe the customisations
195			to these files associated with this experiment.
196
197			\subsubsection{File {\it input/data}}
198
199			This file, reproduced completely below, specifies the main parameters
200			for the experiment. The parameters that are significant for this configuration
201			are
202
203			\begin{itemize}
204
205			\item Line 7, \begin{verbatim} viscAh=4.E2, \end{verbatim} this line sets
206			the laplacian friction coefficient to $400 m^2s^{-1}$
207			\item Line 10, \begin{verbatim} beta=1.E-11, \end{verbatim} this line sets
208			$\beta$ (the gradient of the coriolis parameter, $f$) to $10^{-11} s^{-1}m^{-1}$
209
210			\item Lines 15 and 16
211			\begin{verbatim}
212			rigidLid=.FALSE.,
213			implicitFreeSurface=.TRUE.,
214			\end{verbatim}
215			these lines suppress the rigid lid formulation of the surface
216			pressure inverter and activate the implicit free surface form
217			of the pressure inverter.
218
219			\item Line 27,
220			\begin{verbatim}
221			startTime=0,
222			\end{verbatim}
223			this line indicates that the experiment should start from $t=0$
224			and implicitly supresses searching for checkpoint files associated
225			with restarting an numerical integration from a previously saved state.
226
227			\item Line 29,
228			\begin{verbatim}
229			endTime=12000,
230			\end{verbatim}
231			this line indicates that the experiment should start finish at $t=12000s$.
232			A restart file will be written at this time that will enable the
233			simulation to be continued from this point.
234
235			\item Line 30,
236			\begin{verbatim}
237			deltaTmom=1200,
238			\end{verbatim}
239			This line sets the momentum equation timestep to $1200s$.
240
241			\item Line 39,
242			\begin{verbatim}
243			usingCartesianGrid=.TRUE.,
244			\end{verbatim}
245			This line requests that the simulation be performed in a
246			cartesian coordinate system.
247
248			\item Line 41,
249			\begin{verbatim}
250			delX=60*20E3,
251			\end{verbatim}
252			This line sets the horizontal grid spacing between each x-coordinate line
253			in the discrete grid. The syntax indicates that the discrete grid
254			should be comprise of $60$ grid lines each separated by $20 \times 10^{3}m$
255			($20$~km).
256
257			\item Line 42,
258			\begin{verbatim}
259			delY=60*20E3,
260			\end{verbatim}
261			This line sets the horizontal grid spacing between each y-coordinate line
262			in the discrete grid to $20 \times 10^{3}m$ ($20$~km).
263
264			\item Line 43,
265			\begin{verbatim}
266			delZ=5000,
267			\end{verbatim}
268			This line sets the vertical grid spacing between each z-coordinate line
269			in the discrete grid to $5000m$ ($5$~km).
270
271			\item Line 46,
272			\begin{verbatim}
273			bathyFile='topog.box'
274			\end{verbatim}
275			This line specifies the name of the file from which the domain
276			bathymetry is read. This file is a two-dimensional ($x,y$) map of
277			depths. This file is assumed to contain 64-bit binary numbers
278			giving the depth of the model at each grid cell, ordered with the x
279			coordinate varying fastest. The points are ordered from low coordinate
280			to high coordinate for both axes. The units and orientation of the
281			depths in this file are the same as used in the MITgcm code. In this
282			experiment, a depth of $0m$ indicates a solid wall and a depth
283			of $-5000m$ indicates open ocean. The matlab program
284			{\it input/gendata.m} shows an example of how to generate a
285			bathymetry file.
286
287
288			\item Line 49,
289			\begin{verbatim}
290			zonalWindFile='windx.sin_y'
291			\end{verbatim}
292			This line specifies the name of the file from which the x-direction
293			surface wind stress is read. This file is also a two-dimensional
294			($x,y$) map and is enumerated and formatted in the same manner as the
295			bathymetry file. The matlab program {\it input/gendata.m} includes example
296			code to generate a valid {\bf zonalWindFile} file.
297
298			\end{itemize}
299
300			\noindent other lines in the file {\it input/data} are standard values
301			that are described in the MITgcm Getting Started and MITgcm Parameters
302			notes.
303
304			\begin{small}
305			\input{part3/case_studies/barotropic_gyre/input/data}
306			\end{small}
307
308			\subsubsection{File {\it input/data.pkg}}
309
310			This file uses standard default values and does not contain
311			customisations for this experiment.
312
313			\subsubsection{File {\it input/eedata}}
314
315			This file uses standard default values and does not contain
316			customisations for this experiment.
317
318			\subsubsection{File {\it input/windx.sin\_y}}
319
320			The {\it input/windx.sin\_y} file specifies a two-dimensional ($x,y$)
321			map of wind stress ,$\tau_{x}$, values. The units used are $Nm^{-2}$.
322			Although $\tau_{x}$ is only a function of $y$n in this experiment
323			this file must still define a complete two-dimensional map in order
324			to be compatible with the standard code for loading forcing fields
325			in MITgcm. The included matlab program {\it input/gendata.m} gives a complete
326			code for creating the {\it input/windx.sin\_y} file.
327
328			\subsubsection{File {\it input/topog.box}}
329
330
331			The {\it input/topog.box} file specifies a two-dimensional ($x,y$)
332			map of depth values. For this experiment values are either
333			$0m$ or {\bf -delZ}m, corresponding respectively to a wall or to deep
334			ocean. The file contains a raw binary stream of data that is enumerated
335			in the same way as standard MITgcm two-dimensional, horizontal arrays.
336			The included matlab program {\it input/gendata.m} gives a complete
337			code for creating the {\it input/topog.box} file.
338
339			\subsubsection{File {\it code/SIZE.h}}
340
341			Two lines are customized in this file for the current experiment
342
343			\begin{itemize}
344
345			\item Line 39,
346			\begin{verbatim} sNx=60, \end{verbatim} this line sets
347			the lateral domain extent in grid points for the
348			axis aligned with the x-coordinate.
349
350			\item Line 40,
351			\begin{verbatim} sNy=60, \end{verbatim} this line sets
352			the lateral domain extent in grid points for the
353			axis aligned with the y-coordinate.
354
355			\end{itemize}
356
357			\begin{small}
358			\input{part3/case_studies/barotropic_gyre/code/SIZE.h}
359			\end{small}
360
361			\subsubsection{File {\it code/CPP\_OPTIONS.h}}
362
363			This file uses standard default values and does not contain
364			customisations for this experiment.
365
366
367			\subsubsection{File {\it code/CPP\_EEOPTIONS.h}}
368
369			This file uses standard default values and does not contain
370			customisations for this experiment.
371