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3    
4  %\section{Getting started}  %\section{Getting started}
5    
6  In this section, we describe how to use the model. In the first  We believe the best way to familiarize yourself with the
 section, we provide enough information to help you get started with  
 the model. We believe the best way to familiarize yourself with the  
7  model is to run the case study examples provided with the base  model is to run the case study examples provided with the base
8  version. Information on how to obtain, compile, and run the code is  version. Information on how to obtain, compile, and run the code is
9  found there as well as a brief description of the model structure  found here as well as a brief description of the model structure
10  directory and the case study examples.  The latter and the code  directory and the case study examples. Information is also provided
11  structure are described more fully in chapters  here on how to customize the code when you are ready to try implementing
12  \ref{chap:discretization} and \ref{chap:sarch}, respectively. Here, in  the configuration you have in mind.  The code and algorithm
13  this section, we provide information on how to customize the code when  are described more fully in chapters \ref{chap:discretization} and
14  you are ready to try implementing the configuration you have in mind.  \ref{chap:sarch}.
15    
16  \section{Where to find information}  \section{Where to find information}
17  \label{sect:whereToFindInfo}  \label{sec:whereToFindInfo}
18    \begin{rawhtml}
19    <!-- CMIREDIR:whereToFindInfo: -->
20    \end{rawhtml}
21    
22  A web site is maintained for release 2 (``Pelican'') of MITgcm:  There is a web-archived support mailing list for the model that
 \begin{rawhtml} <A href=http://mitgcm.org/pelican/ target="idontexist"> \end{rawhtml}  
 \begin{verbatim}  
 http://mitgcm.org/pelican  
 \end{verbatim}  
 \begin{rawhtml} </A> \end{rawhtml}  
 Here you will find an on-line version of this document, a  
 ``browsable'' copy of the code and a searchable database of the model  
 and site, as well as links for downloading the model and  
 documentation, to data-sources, and other related sites.  
   
 There is also a web-archived support mailing list for the model that  
23  you can email at \texttt{MITgcm-support@mitgcm.org} or browse at:  you can email at \texttt{MITgcm-support@mitgcm.org} or browse at:
24  \begin{rawhtml} <A href=http://mitgcm.org/mailman/listinfo/mitgcm-support/ target="idontexist"> \end{rawhtml}  \begin{rawhtml} <A href=http://mitgcm.org/mailman/listinfo/mitgcm-support/ target="idontexist"> \end{rawhtml}
25  \begin{verbatim}  \begin{verbatim}
# Line 37  http://mitgcm.org/mailman/listinfo/mitgc Line 27  http://mitgcm.org/mailman/listinfo/mitgc
27  http://mitgcm.org/pipermail/mitgcm-support/  http://mitgcm.org/pipermail/mitgcm-support/
28  \end{verbatim}  \end{verbatim}
29  \begin{rawhtml} </A> \end{rawhtml}  \begin{rawhtml} </A> \end{rawhtml}
 Essentially all of the MITgcm web pages can be searched using a  
 popular web crawler such as Google or through our own search facility:  
 \begin{rawhtml} <A href=http://mitgcm.org/mailman/htdig/ target="idontexist"> \end{rawhtml}  
 \begin{verbatim}  
 http://mitgcm.org/htdig/  
 \end{verbatim}  
 \begin{rawhtml} </A> \end{rawhtml}  
 %%% http://www.google.com/search?q=hydrostatic+site%3Amitgcm.org  
   
   
30    
31  \section{Obtaining the code}  \section{Obtaining the code}
32  \label{sect:obtainingCode}  \label{sec:obtainingCode}
33    \begin{rawhtml}
34    <!-- CMIREDIR:obtainingCode: -->
35    \end{rawhtml}
36    
37  MITgcm can be downloaded from our system by following  MITgcm can be downloaded from our system by following
38  the instructions below. As a courtesy we ask that you send e-mail to us at  the instructions below. As a courtesy we ask that you send e-mail to us at
# Line 79  provide easy support for maintenance upd Line 62  provide easy support for maintenance upd
62    
63  \end{enumerate}  \end{enumerate}
64    
65    \subsection{Method 1 - Checkout from CVS}
66    \label{sec:cvs_checkout}
67    
68  If CVS is available on your system, we strongly encourage you to use it. CVS  If CVS is available on your system, we strongly encourage you to use it. CVS
69  provides an efficient and elegant way of organizing your code and keeping  provides an efficient and elegant way of organizing your code and keeping
70  track of your changes. If CVS is not available on your machine, you can also  track of your changes. If CVS is not available on your machine, you can also
# Line 89  be set within your shell.  For a csh or Line 75  be set within your shell.  For a csh or
75  \begin{verbatim}  \begin{verbatim}
76  % setenv CVSROOT :pserver:cvsanon@mitgcm.org:/u/gcmpack  % setenv CVSROOT :pserver:cvsanon@mitgcm.org:/u/gcmpack
77  \end{verbatim}  \end{verbatim}
78  in your .cshrc or .tcshrc file.  For bash or sh shells, put:  in your \texttt{.cshrc} or \texttt{.tcshrc} file.  For bash or sh
79    shells, put:
80  \begin{verbatim}  \begin{verbatim}
81  % export CVSROOT=':pserver:cvsanon@mitgcm.org:/u/gcmpack'  % export CVSROOT=':pserver:cvsanon@mitgcm.org:/u/gcmpack'
82  \end{verbatim}  \end{verbatim}
83  in your .profile or .bashrc file.  in your \texttt{.profile} or \texttt{.bashrc} file.
84    
85    
86  To get MITgcm through CVS, first register with the MITgcm CVS server  To get MITgcm through CVS, first register with the MITgcm CVS server
# Line 105  You only need to do a ``cvs login'' once Line 92  You only need to do a ``cvs login'' once
92    
93  To obtain the latest sources type:  To obtain the latest sources type:
94  \begin{verbatim}  \begin{verbatim}
95  % cvs co MITgcm  % cvs co -P MITgcm
96  \end{verbatim}  \end{verbatim}
97  or to get a specific release type:  or to get a specific release type:
98  \begin{verbatim}  \begin{verbatim}
99  % cvs co -P -r checkpoint52i_post  MITgcm  % cvs co -P -r checkpoint52i_post MITgcm
100  \end{verbatim}  \end{verbatim}
101    The CVS command ``\texttt{cvs co}'' is the abreviation of the full-name
102    ``\texttt{cvs checkout}'' command and using the option ``-P'' (\texttt{cvs co -P})
103    will prevent to download unnecessary empty directories.
104    
105  The MITgcm web site contains further directions concerning the source  The MITgcm web site contains further directions concerning the source
106  code and CVS.  It also contains a web interface to our CVS archive so  code and CVS.  It also contains a web interface to our CVS archive so
107  that one may easily view the state of files, revisions, and other  that one may easily view the state of files, revisions, and other
108  development milestones:  development milestones:
109  \begin{rawhtml} <A href=''http://mitgcm.org/download'' target="idontexist"> \end{rawhtml}  \begin{rawhtml} <A href="http://mitgcm.org/viewvc/MITgcm/MITgcm/" target="idontexist"> \end{rawhtml}
110  \begin{verbatim}  \begin{verbatim}
111  http://mitgcm.org/source_code.html  http://mitgcm.org/viewvc/MITgcm/MITgcm/
112  \end{verbatim}  \end{verbatim}
113  \begin{rawhtml} </A> \end{rawhtml}  \begin{rawhtml} </A> \end{rawhtml}
114    
115    As a convenience, the MITgcm CVS server contains aliases which are
116    named subsets of the codebase.  These aliases can be especially
117    helpful when used over slow internet connections or on machines with
118    restricted storage space.  Table \ref{tab:cvsModules} contains a list
119    of CVS aliases
120    \begin{table}[htb]
121      \centering
122      \begin{tabular}[htb]{|lp{3.25in}|}\hline
123        \textbf{Alias Name}    &  \textbf{Information (directories) Contained}  \\\hline
124        \texttt{MITgcm\_code}  &  Only the source code -- none of the verification examples.  \\
125        \texttt{MITgcm\_verif\_basic}
126        &  Source code plus a small set of the verification examples
127        (\texttt{global\_ocean.90x40x15}, \texttt{aim.5l\_cs}, \texttt{hs94.128x64x5},
128        \texttt{front\_relax}, and \texttt{plume\_on\_slope}).  \\
129        \texttt{MITgcm\_verif\_atmos}  &  Source code plus all of the atmospheric examples.  \\
130        \texttt{MITgcm\_verif\_ocean}  &  Source code plus all of the oceanic examples.  \\
131        \texttt{MITgcm\_verif\_all}    &  Source code plus all of the
132        verification examples. \\\hline
133      \end{tabular}
134      \caption{MITgcm CVS Modules}
135      \label{tab:cvsModules}
136    \end{table}
137    
138  The checkout process creates a directory called \textit{MITgcm}. If  The checkout process creates a directory called \texttt{MITgcm}. If
139  the directory \textit{MITgcm} exists this command updates your code  the directory \texttt{MITgcm} exists this command updates your code
140  based on the repository. Each directory in the source tree contains a  based on the repository. Each directory in the source tree contains a
141  directory \textit{CVS}. This information is required by CVS to keep  directory \texttt{CVS}. This information is required by CVS to keep
142  track of your file versions with respect to the repository. Don't edit  track of your file versions with respect to the repository. Don't edit
143  the files in \textit{CVS}!  You can also use CVS to download code  the files in \texttt{CVS}!  You can also use CVS to download code
144  updates.  More extensive information on using CVS for maintaining  updates.  More extensive information on using CVS for maintaining
145  MITgcm code can be found  MITgcm code can be found
146  \begin{rawhtml} <A href=''http://mitgcm.org/usingcvstoget.html'' target="idontexist"> \end{rawhtml}  \begin{rawhtml} <A href="http://mitgcm.org/public/using_cvs.html" target="idontexist"> \end{rawhtml}
147  here  here
148  \begin{rawhtml} </A> \end{rawhtml}  \begin{rawhtml} </A> \end{rawhtml}
149  .  .
150    It is important to note that the CVS aliases in Table
151    \ref{tab:cvsModules} cannot be used in conjunction with the CVS
152  \paragraph*{Conventional download method}  \texttt{-d DIRNAME} option.  However, the \texttt{MITgcm} directories
153  \label{sect:conventionalDownload}  they create can be changed to a different name following the check-out:
   
 If you do not have CVS on your system, you can download the model as a  
 tar file from the web site at:  
 \begin{rawhtml} <A href=http://mitgcm.org/download target="idontexist"> \end{rawhtml}  
154  \begin{verbatim}  \begin{verbatim}
155  http://mitgcm.org/download/     %  cvs co -P MITgcm_verif_basic
156       %  mv MITgcm MITgcm_verif_basic
157  \end{verbatim}  \end{verbatim}
 \begin{rawhtml} </A> \end{rawhtml}  
 The tar file still contains CVS information which we urge you not to  
 delete; even if you do not use CVS yourself the information can help  
 us if you should need to send us your copy of the code.  If a recent  
 tar file does not exist, then please contact the developers through  
 the  
 \begin{rawhtml} <A href=''mailto:MITgcm-support@mitgcm.org"> \end{rawhtml}  
 MITgcm-support@mitgcm.org  
 \begin{rawhtml} </A> \end{rawhtml}  
 mailing list.  
158    
159  \paragraph*{Upgrading from an earlier version}  \subsubsection{Upgrading from an earlier version}
160    
161  If you already have an earlier version of the code you can ``upgrade''  If you already have an earlier version of the code you can ``upgrade''
162  your copy instead of downloading the entire repository again. First,  your copy instead of downloading the entire repository again. First,
# Line 166  your copy instead of downloading the ent Line 166  your copy instead of downloading the ent
166  \end{verbatim}  \end{verbatim}
167  and then issue the cvs update command such as:  and then issue the cvs update command such as:
168  \begin{verbatim}  \begin{verbatim}
169  % cvs -q update -r checkpoint52i_post -d -P  % cvs -q update -d -P -r checkpoint52i_post
170  \end{verbatim}  \end{verbatim}
171  This will update the ``tag'' to ``checkpoint52i\_post'', add any new  This will update the ``tag'' to ``checkpoint52i\_post'', add any new
172  directories (-d) and remove any empty directories (-P). The -q option  directories (-d) and remove any empty directories (-P). The -q option
# Line 212  have run into a problem for which ``we h Line 212  have run into a problem for which ``we h
212  latest code'' and we haven't made a ``tag'' or ``release'' since that  latest code'' and we haven't made a ``tag'' or ``release'' since that
213  patch then you'll need to get the latest code:  patch then you'll need to get the latest code:
214  \begin{verbatim}  \begin{verbatim}
215  % cvs -q update -A -d -P  % cvs -q update -d -P -A
216  \end{verbatim}  \end{verbatim}
217  Unlike, the ``check-out'' and ``update'' procedures above, there is no  Unlike, the ``check-out'' and ``update'' procedures above, there is no
218  ``tag'' or release name. The -A tells CVS to upgrade to the  ``tag'' or release name. The -A tells CVS to upgrade to the
# Line 222  that you may only have part of a patch. Line 222  that you may only have part of a patch.
222  also means we can't tell what version of the code you are working  also means we can't tell what version of the code you are working
223  with. So please be sure you understand what you're doing.  with. So please be sure you understand what you're doing.
224    
225    \subsection{Method 2 - Tar file download}
226    \label{sec:conventionalDownload}
227    
228    If you do not have CVS on your system, you can download the model as a
229    tar file from the web site at:
230    \begin{rawhtml} <A href=http://mitgcm.org/download/ target="idontexist"> \end{rawhtml}
231    \begin{verbatim}
232    http://mitgcm.org/download/
233    \end{verbatim}
234    \begin{rawhtml} </A> \end{rawhtml}
235    The tar file still contains CVS information which we urge you not to
236    delete; even if you do not use CVS yourself the information can help
237    us if you should need to send us your copy of the code.  If a recent
238    tar file does not exist, then please contact the developers through
239    the
240    \begin{rawhtml} <A href="mailto:MITgcm-support@mitgcm.org"> \end{rawhtml}
241    MITgcm-support@mitgcm.org
242    \begin{rawhtml} </A> \end{rawhtml}
243    mailing list.
244    
245  \section{Model and directory structure}  \section{Model and directory structure}
246    \begin{rawhtml}
247    <!-- CMIREDIR:directory_structure: -->
248    \end{rawhtml}
249    
250  The ``numerical'' model is contained within a execution environment  The ``numerical'' model is contained within a execution environment
251  support wrapper. This wrapper is designed to provide a general  support wrapper. This wrapper is designed to provide a general
# Line 230  framework for grid-point models. MITgcmU Line 253  framework for grid-point models. MITgcmU
253  model that uses the framework. Under this structure the model is split  model that uses the framework. Under this structure the model is split
254  into execution environment support code and conventional numerical  into execution environment support code and conventional numerical
255  model code. The execution environment support code is held under the  model code. The execution environment support code is held under the
256  \textit{eesupp} directory. The grid point model code is held under the  \texttt{eesupp} directory. The grid point model code is held under the
257  \textit{model} directory. Code execution actually starts in the  \texttt{model} directory. Code execution actually starts in the
258  \textit{eesupp} routines and not in the \textit{model} routines. For  \texttt{eesupp} routines and not in the \texttt{model} routines. For
259  this reason the top-level \textit{MAIN.F} is in the  this reason the top-level \texttt{MAIN.F} is in the
260  \textit{eesupp/src} directory. In general, end-users should not need  \texttt{eesupp/src} directory. In general, end-users should not need
261  to worry about this level. The top-level routine for the numerical  to worry about this level. The top-level routine for the numerical
262  part of the code is in \textit{model/src/THE\_MODEL\_MAIN.F}. Here is  part of the code is in \texttt{model/src/THE\_MODEL\_MAIN.F}. Here is
263  a brief description of the directory structure of the model under the  a brief description of the directory structure of the model under the
264  root tree (a detailed description is given in section 3: Code  root tree (a detailed description is given in section 3: Code
265  structure).  structure).
266    
267  \begin{itemize}  \begin{itemize}
268    
269  \item \textit{bin}: this directory is initially empty. It is the  \item \texttt{doc}: contains brief documentation notes.
   default directory in which to compile the code.  
     
 \item \textit{diags}: contains the code relative to time-averaged  
   diagnostics. It is subdivided into two subdirectories \textit{inc}  
   and \textit{src} that contain include files (*.\textit{h} files) and  
   Fortran subroutines (*.\textit{F} files), respectively.  
   
 \item \textit{doc}: contains brief documentation notes.  
     
 \item \textit{eesupp}: contains the execution environment source code.  
   Also subdivided into two subdirectories \textit{inc} and  
   \textit{src}.  
     
 \item \textit{exe}: this directory is initially empty. It is the  
   default directory in which to execute the code.  
270        
271  \item \textit{model}: this directory contains the main source code.  \item \texttt{eesupp}: contains the execution environment source code.
272    Also subdivided into two subdirectories \textit{inc} and    Also subdivided into two subdirectories \texttt{inc} and
273    \textit{src}.    \texttt{src}.
274      
275    \item \texttt{model}: this directory contains the main source code.
276      Also subdivided into two subdirectories \texttt{inc} and
277      \texttt{src}.
278        
279  \item \textit{pkg}: contains the source code for the packages. Each  \item \texttt{pkg}: contains the source code for the packages. Each
280    package corresponds to a subdirectory. For example, \textit{gmredi}    package corresponds to a subdirectory. For example, \texttt{gmredi}
281    contains the code related to the Gent-McWilliams/Redi scheme,    contains the code related to the Gent-McWilliams/Redi scheme,
282    \textit{aim} the code relative to the atmospheric intermediate    \texttt{aim} the code relative to the atmospheric intermediate
283    physics. The packages are described in detail in section 3.    physics. The packages are described in detail in chapter \ref{chap:packagesI}.
284        
285  \item \textit{tools}: this directory contains various useful tools.  \item \texttt{tools}: this directory contains various useful tools.
286    For example, \textit{genmake2} is a script written in csh (C-shell)    For example, \texttt{genmake2} is a script written in csh (C-shell)
287    that should be used to generate your makefile. The directory    that should be used to generate your makefile. The directory
288    \textit{adjoint} contains the makefile specific to the Tangent    \texttt{adjoint} contains the makefile specific to the Tangent
289    linear and Adjoint Compiler (TAMC) that generates the adjoint code.    linear and Adjoint Compiler (TAMC) that generates the adjoint code.
290    The latter is described in details in part V.    The latter is described in detail in part \ref{chap.ecco}.
291      This directory also contains the subdirectory build\_options, which
292      contains the `optfiles' with the compiler options for the different
293      compilers and machines that can run MITgcm.
294        
295  \item \textit{utils}: this directory contains various utilities. The  \item \texttt{utils}: this directory contains various utilities. The
296    subdirectory \textit{knudsen2} contains code and a makefile that    subdirectory \texttt{knudsen2} contains code and a makefile that
297    compute coefficients of the polynomial approximation to the knudsen    compute coefficients of the polynomial approximation to the knudsen
298    formula for an ocean nonlinear equation of state. The    formula for an ocean nonlinear equation of state. The
299    \textit{matlab} subdirectory contains matlab scripts for reading    \texttt{matlab} subdirectory contains matlab scripts for reading
300    model output directly into matlab. \textit{scripts} contains C-shell    model output directly into matlab. \texttt{scripts} contains C-shell
301    post-processing scripts for joining processor-based and tiled-based    post-processing scripts for joining processor-based and tiled-based
302    model output.    model output. The subdirectory exch2 contains the code needed for
303      the exch2 package to work with different combinations of domain
304      decompositions.
305        
306  \item \textit{verification}: this directory contains the model  \item \texttt{verification}: this directory contains the model
307    examples. See section \ref{sect:modelExamples}.    examples. See section \ref{sec:modelExamples}.
   
 \end{itemize}  
   
 \section{Example experiments}  
 \label{sect:modelExamples}  
308    
309  %% a set of twenty-four pre-configured numerical experiments  \item \texttt{jobs}: contains sample job scripts for running MITgcm.
   
 The MITgcm distribution comes with more than a dozen pre-configured  
 numerical experiments. Some of these example experiments are tests of  
 individual parts of the model code, but many are fully fledged  
 numerical simulations. A few of the examples are used for tutorial  
 documentation in sections \ref{sect:eg-baro} - \ref{sect:eg-global}.  
 The other examples follow the same general structure as the tutorial  
 examples. However, they only include brief instructions in a text file  
 called {\it README}.  The examples are located in subdirectories under  
 the directory \textit{verification}. Each example is briefly described  
 below.  
   
 \subsection{Full list of model examples}  
   
 \begin{enumerate}  
     
 \item \textit{exp0} - single layer, ocean double gyre (barotropic with  
   free-surface). This experiment is described in detail in section  
   \ref{sect:eg-baro}.  
   
 \item \textit{exp1} - Four layer, ocean double gyre. This experiment  
   is described in detail in section \ref{sect:eg-baroc}.  
     
 \item \textit{exp2} - 4x4 degree global ocean simulation with steady  
   climatological forcing. This experiment is described in detail in  
   section \ref{sect:eg-global}.  
     
 \item \textit{exp4} - Flow over a Gaussian bump in open-water or  
   channel with open boundaries.  
     
 \item \textit{exp5} - Inhomogenously forced ocean convection in a  
   doubly periodic box.  
   
 \item \textit{front\_relax} - Relaxation of an ocean thermal front (test for  
 Gent/McWilliams scheme). 2D (Y-Z).  
   
 \item \textit{internal wave} - Ocean internal wave forced by open  
   boundary conditions.  
     
 \item \textit{natl\_box} - Eastern subtropical North Atlantic with KPP  
   scheme; 1 month integration  
     
 \item \textit{hs94.1x64x5} - Zonal averaged atmosphere using Held and  
   Suarez '94 forcing.  
     
 \item \textit{hs94.128x64x5} - 3D atmosphere dynamics using Held and  
   Suarez '94 forcing.  
     
 \item \textit{hs94.cs-32x32x5} - 3D atmosphere dynamics using Held and  
   Suarez '94 forcing on the cubed sphere.  
     
 \item \textit{aim.5l\_zon-ave} - Intermediate Atmospheric physics.  
   Global Zonal Mean configuration, 1x64x5 resolution.  
     
 \item \textit{aim.5l\_XZ\_Equatorial\_Slice} - Intermediate  
   Atmospheric physics, equatorial Slice configuration.  2D (X-Z).  
     
 \item \textit{aim.5l\_Equatorial\_Channel} - Intermediate Atmospheric  
   physics. 3D Equatorial Channel configuration.  
     
 \item \textit{aim.5l\_LatLon} - Intermediate Atmospheric physics.  
   Global configuration, on latitude longitude grid with 128x64x5 grid  
   points ($2.8^\circ{\rm degree}$ resolution).  
     
 \item \textit{adjustment.128x64x1} Barotropic adjustment problem on  
   latitude longitude grid with 128x64 grid points ($2.8^\circ{\rm  
     degree}$ resolution).  
     
 \item \textit{adjustment.cs-32x32x1} Barotropic adjustment problem on  
   cube sphere grid with 32x32 points per face ( roughly $2.8^\circ{\rm  
     degree}$ resolution).  
     
 \item \textit{advect\_cs} Two-dimensional passive advection test on  
   cube sphere grid.  
     
 \item \textit{advect\_xy} Two-dimensional (horizontal plane) passive  
   advection test on Cartesian grid.  
     
 \item \textit{advect\_yz} Two-dimensional (vertical plane) passive  
   advection test on Cartesian grid.  
310        
311  \item \textit{carbon} Simple passive tracer experiment. Includes  \item \texttt{lsopt}: Line search code used for optimization.
   derivative calculation. Described in detail in section  
   \ref{sect:eg-carbon-ad}.  
   
 \item \textit{flt\_example} Example of using float package.  
     
 \item \textit{global\_ocean.90x40x15} Global circulation with GM, flux  
   boundary conditions and poles.  
   
 \item \textit{global\_ocean\_pressure} Global circulation in pressure  
   coordinate (non-Boussinesq ocean model). Described in detail in  
   section \ref{sect:eg-globalpressure}.  
     
 \item \textit{solid-body.cs-32x32x1} Solid body rotation test for cube  
   sphere grid.  
   
 \end{enumerate}  
   
 \subsection{Directory structure of model examples}  
   
 Each example directory has the following subdirectories:  
   
 \begin{itemize}  
 \item \textit{code}: contains the code particular to the example. At a  
   minimum, this directory includes the following files:  
   
   \begin{itemize}  
   \item \textit{code/CPP\_EEOPTIONS.h}: declares CPP keys relative to  
     the ``execution environment'' part of the code. The default  
     version is located in \textit{eesupp/inc}.  
     
   \item \textit{code/CPP\_OPTIONS.h}: declares CPP keys relative to  
     the ``numerical model'' part of the code. The default version is  
     located in \textit{model/inc}.  
     
   \item \textit{code/SIZE.h}: declares size of underlying  
     computational grid.  The default version is located in  
     \textit{model/inc}.  
   \end{itemize}  
     
   In addition, other include files and subroutines might be present in  
   \textit{code} depending on the particular experiment. See Section 2  
   for more details.  
     
 \item \textit{input}: contains the input data files required to run  
   the example. At a minimum, the \textit{input} directory contains the  
   following files:  
   
   \begin{itemize}  
   \item \textit{input/data}: this file, written as a namelist,  
     specifies the main parameters for the experiment.  
     
   \item \textit{input/data.pkg}: contains parameters relative to the  
     packages used in the experiment.  
312        
313    \item \textit{input/eedata}: this file contains ``execution  \item \texttt{optim}: Interface between MITgcm and line search code.
     environment'' data. At present, this consists of a specification  
     of the number of threads to use in $X$ and $Y$ under multithreaded  
     execution.  
   \end{itemize}  
314        
   In addition, you will also find in this directory the forcing and  
   topography files as well as the files describing the initial state  
   of the experiment.  This varies from experiment to experiment. See  
   section 2 for more details.  
   
 \item \textit{results}: this directory contains the output file  
   \textit{output.txt} produced by the simulation example. This file is  
   useful for comparison with your own output when you run the  
   experiment.  
315  \end{itemize}  \end{itemize}
316    
317  Once you have chosen the example you want to run, you are ready to  \section[Building MITgcm]{Building the code}
318    \label{sec:buildingCode}
319    \begin{rawhtml}
320    <!-- CMIREDIR:buildingCode: -->
321    \end{rawhtml}
322    
323    To compile the code, we use the \texttt{make} program. This uses a
324    file (\texttt{Makefile}) that allows us to pre-process source files,
325    specify compiler and optimization options and also figures out any
326    file dependencies. We supply a script (\texttt{genmake2}), described
327    in section \ref{sec:genmake}, that automatically creates the
328    \texttt{Makefile} for you. You then need to build the dependencies and
329  compile the code.  compile the code.
330    
331  \section{Building the code}  As an example, assume that you want to build and run experiment
332  \label{sect:buildingCode}  \texttt{verification/exp2}. The are multiple ways and places to
   
 To compile the code, we use the {\em make} program. This uses a file  
 ({\em Makefile}) that allows us to pre-process source files, specify  
 compiler and optimization options and also figures out any file  
 dependencies. We supply a script ({\em genmake2}), described in  
 section \ref{sect:genmake}, that automatically creates the {\em  
   Makefile} for you. You then need to build the dependencies and  
 compile the code.  
   
 As an example, let's assume that you want to build and run experiment  
 \textit{verification/exp2}. The are multiple ways and places to  
333  actually do this but here let's build the code in  actually do this but here let's build the code in
334  \textit{verification/exp2/input}:  \texttt{verification/exp2/build}:
335  \begin{verbatim}  \begin{verbatim}
336  % cd verification/exp2/input  % cd verification/exp2/build
337  \end{verbatim}  \end{verbatim}
338  First, build the {\em Makefile}:  First, build the \texttt{Makefile}:
339  \begin{verbatim}  \begin{verbatim}
340  % ../../../tools/genmake2 -mods=../code  % ../../../tools/genmake2 -mods=../code
341  \end{verbatim}  \end{verbatim}
342  The command line option tells {\em genmake} to override model source  The command line option tells \texttt{genmake} to override model source
343  code with any files in the directory {\em ./code/}.  code with any files in the directory \texttt{../code/}.
344    
345  On many systems, the {\em genmake2} program will be able to  On many systems, the \texttt{genmake2} program will be able to
346  automatically recognize the hardware, find compilers and other tools  automatically recognize the hardware, find compilers and other tools
347  within the user's path (``echo \$PATH''), and then choose an  within the user's path (``\texttt{echo \$PATH}''), and then choose an
348  appropriate set of options from the files contained in the {\em  appropriate set of options from the files (``optfiles'') contained in
349    tools/build\_options} directory.  Under some circumstances, a user  the \texttt{tools/build\_options} directory.  Under some
350  may have to create a new ``optfile'' in order to specify the exact  circumstances, a user may have to create a new ``optfile'' in order to
351  combination of compiler, compiler flags, libraries, and other options  specify the exact combination of compiler, compiler flags, libraries,
352  necessary to build a particular configuration of MITgcm.  In such  and other options necessary to build a particular configuration of
353  cases, it is generally helpful to read the existing ``optfiles'' and  MITgcm.  In such cases, it is generally helpful to read the existing
354  mimic their syntax.  ``optfiles'' and mimic their syntax.
355    
356  Through the MITgcm-support list, the MITgcm developers are willing to  Through the MITgcm-support list, the MITgcm developers are willing to
357  provide help writing or modifing ``optfiles''.  And we encourage users  provide help writing or modifing ``optfiles''.  And we encourage users
358  to post new ``optfiles'' (particularly ones for new machines or  to post new ``optfiles'' (particularly ones for new machines or
359  architectures) to the  architectures) to the
360  \begin{rawhtml} <A href=''mailto:MITgcm-support@mitgcm.org"> \end{rawhtml}  \begin{rawhtml} <A href="mailto:MITgcm-support@mitgcm.org"> \end{rawhtml}
361  MITgcm-support@mitgcm.org  MITgcm-support@mitgcm.org
362  \begin{rawhtml} </A> \end{rawhtml}  \begin{rawhtml} </A> \end{rawhtml}
363  list.  list.
364    
365  To specify an optfile to {\em genmake2}, the syntax is:  To specify an optfile to \texttt{genmake2}, the syntax is:
366  \begin{verbatim}  \begin{verbatim}
367  % ../../../tools/genmake2 -mods=../code -of /path/to/optfile  % ../../../tools/genmake2 -mods=../code -of /path/to/optfile
368  \end{verbatim}  \end{verbatim}
369    
370  Once a {\em Makefile} has been generated, we create the dependencies:  Once a \texttt{Makefile} has been generated, we create the
371    dependencies with the command:
372  \begin{verbatim}  \begin{verbatim}
373  % make depend  % make depend
374  \end{verbatim}  \end{verbatim}
375  This modifies the {\em Makefile} by attaching a [long] list of files  This modifies the \texttt{Makefile} by attaching a (usually, long)
376  upon which other files depend. The purpose of this is to reduce  list of files upon which other files depend. The purpose of this is to
377  re-compilation if and when you start to modify the code. The {\tt make  reduce re-compilation if and when you start to modify the code. The
378    depend} command also creates links from the model source to this  {\tt make depend} command also creates links from the model source to
379  directory.  this directory.  It is important to note that the {\tt make depend}
380    stage will occasionally produce warnings or errors since the
381    dependency parsing tool is unable to find all of the necessary header
382    files (\textit{eg.}  \texttt{netcdf.inc}).  In these circumstances, it
383    is usually OK to ignore the warnings/errors and proceed to the next
384    step.
385    
386  Next compile the code:  Next one can compile the code using:
387  \begin{verbatim}  \begin{verbatim}
388  % make  % make
389  \end{verbatim}  \end{verbatim}
390  The {\tt make} command creates an executable called \textit{mitgcmuv}.  The {\tt make} command creates an executable called \texttt{mitgcmuv}.
391  Additional make ``targets'' are defined within the makefile to aid in  Additional make ``targets'' are defined within the makefile to aid in
392  the production of adjoint and other versions of MITgcm.  the production of adjoint and other versions of MITgcm.  On SMP
393    (shared multi-processor) systems, the build process can often be sped
394    up appreciably using the command:
395    \begin{verbatim}
396    % make -j 2
397    \end{verbatim}
398    where the ``2'' can be replaced with a number that corresponds to the
399    number of CPUs available.
400    
401  Now you are ready to run the model. General instructions for doing so are  Now you are ready to run the model. General instructions for doing so are
402  given in section \ref{sect:runModel}. Here, we can run the model with:  given in section \ref{sec:runModel}. Here, we can run the model by
403    first creating links to all the input files:
404    \begin{verbatim}
405    ln -s ../input/* .
406    \end{verbatim}
407    and then calling the executable with:
408  \begin{verbatim}  \begin{verbatim}
409  ./mitgcmuv > output.txt  ./mitgcmuv > output.txt
410  \end{verbatim}  \end{verbatim}
411  where we are re-directing the stream of text output to the file {\em  where we are re-directing the stream of text output to the file
412  output.txt}.  \texttt{output.txt}.
   
413    
414  \subsection{Building/compiling the code elsewhere}  \subsection{Building/compiling the code elsewhere}
415    
416  In the example above (section \ref{sect:buildingCode}) we built the  In the example above (section \ref{sec:buildingCode}) we built the
417  executable in the {\em input} directory of the experiment for  executable in the {\em input} directory of the experiment for
418  convenience. You can also configure and compile the code in other  convenience. You can also configure and compile the code in other
419  locations, for example on a scratch disk with out having to copy the  locations, for example on a scratch disk with out having to copy the
# Line 633  the one experiment: Line 516  the one experiment:
516  \end{verbatim}  \end{verbatim}
517    
518    
519    \subsection{Using \texttt{genmake2}}
520  \subsection{Using \textit{genmake2}}  \label{sec:genmake}
 \label{sect:genmake}  
521    
522  To compile the code, first use the program \texttt{genmake2} (located  To compile the code, first use the program \texttt{genmake2} (located
523  in the \textit{tools} directory) to generate a Makefile.  in the \texttt{tools} directory) to generate a Makefile.
524  \texttt{genmake2} is a shell script written to work with all  \texttt{genmake2} is a shell script written to work with all
525  ``sh''--compatible shells including bash v1, bash v2, and Bourne.  ``sh''--compatible shells including bash v1, bash v2, and Bourne.
526  Internally, \texttt{genmake2} determines the locations of needed  %Internally, \texttt{genmake2} determines the locations of needed
527  files, the compiler, compiler options, libraries, and Unix tools.  It  %files, the compiler, compiler options, libraries, and Unix tools.  It
528  relies upon a number of ``optfiles'' located in the {\em  %relies upon a number of ``optfiles'' located in the
529    tools/build\_options} directory.  %\texttt{tools/build\_options} directory.
530    \texttt{genmake2} parses information from the following sources:
531    \begin{description}
532    \item[-] a {\em gemake\_local} file if one is found in the current
533      directory
534    \item[-] command-line options
535    \item[-] an "options file" as specified by the command-line option
536      \texttt{--optfile=/PATH/FILENAME}
537    \item[-] a {\em packages.conf} file (if one is found) with the
538      specific list of packages to compile. The search path for
539      file {\em packages.conf} is, first, the current directory and
540      then each of the "MODS" directories in the given order (see below).
541    \end{description}
542    
543    \subsubsection{Optfiles in \texttt{tools/build\_options} directory:}
544    
545  The purpose of the optfiles is to provide all the compilation options  The purpose of the optfiles is to provide all the compilation options
546  for particular ``platforms'' (where ``platform'' roughly means the  for particular ``platforms'' (where ``platform'' roughly means the
# Line 717  for inclusion.  Please send the file to Line 613  for inclusion.  Please send the file to
613  \begin{rawhtml} </A> \end{rawhtml}  \begin{rawhtml} </A> \end{rawhtml}
614  mailing list.  mailing list.
615    
616    \subsubsection{Command-line options:}
617    
618  In addition to the optfiles, \texttt{genmake2} supports a number of  In addition to the optfiles, \texttt{genmake2} supports a number of
619  helpful command-line options.  A complete list of these options can be  helpful command-line options.  A complete list of these options can be
620  obtained from:  obtained from:
# Line 739  The most important command-line options Line 637  The most important command-line options
637    the user's path.  When these three items have been identified,    the user's path.  When these three items have been identified,
638    genmake2 will try to find an optfile that has a matching name.    genmake2 will try to find an optfile that has a matching name.
639        
640    \item[\texttt{--mods='DIR1 DIR2 DIR3 ...'}] specifies a list of
641      directories containing ``modifications''.  These directories contain
642      files with names that may (or may not) exist in the main MITgcm
643      source tree but will be overridden by any identically-named sources
644      within the ``MODS'' directories.
645      
646      The order of precedence for this "name-hiding" is as follows:
647      \begin{itemize}
648      \item ``MODS'' directories (in the order given)
649      \item Packages either explicitly specified or provided by default
650        (in the order given)
651      \item Packages included due to package dependencies (in the order
652        that that package dependencies are parsed)
653      \item The "standard dirs" (which may have been specified by the
654        ``-standarddirs'' option)
655      \end{itemize}
656      
657    \item[\texttt{--pgroups=/PATH/FILENAME}] specifies the file
658      where package groups are defined. If not set, the package-groups
659      definition will be read from {\em pkg/pkg\_groups}.
660      It also contains the default list of packages (defined
661      as the group ``{\it default\_pkg\_list}'' which is used
662      when no specific package list ({\em packages.conf})
663      is found in current directory or in any "MODS" directory.
664    
665  \item[\texttt{--pdepend=/PATH/FILENAME}] specifies the dependency file  \item[\texttt{--pdepend=/PATH/FILENAME}] specifies the dependency file
666    used for packages.    used for packages.
667        
# Line 751  The most important command-line options Line 674  The most important command-line options
674    assumed that the two packages are compatible and will function    assumed that the two packages are compatible and will function
675    either with or without each other.    either with or without each other.
676        
 \item[\texttt{--pdefault='PKG1 PKG2 PKG3 ...'}] specifies the default  
   set of packages to be used.  
     
   If not set, the default package list will be read from {\em  
     pkg/pkg\_default}  
     
677  \item[\texttt{--adof=/path/to/file}] specifies the "adjoint" or  \item[\texttt{--adof=/path/to/file}] specifies the "adjoint" or
678    automatic differentiation options file to be used.  The file is    automatic differentiation options file to be used.  The file is
679    analogous to the ``optfile'' defined above but it specifies    analogous to the ``optfile'' defined above but it specifies
# Line 769  The most important command-line options Line 686  The most important command-line options
686    "STAF" compiler.  As with any compilers, it is helpful to have their    "STAF" compiler.  As with any compilers, it is helpful to have their
687    directories listed in your {\tt \$PATH} environment variable.    directories listed in your {\tt \$PATH} environment variable.
688        
689  \item[\texttt{--mods='DIR1 DIR2 DIR3 ...'}] specifies a list of  \item[\texttt{--mpi}] This option enables certain MPI features (using
690    directories containing ``modifications''.  These directories contain    CPP \texttt{\#define}s) within the code and is necessary for MPI
691    files with names that may (or may not) exist in the main MITgcm    builds (see Section \ref{sec:mpi-build}).
   source tree but will be overridden by any identically-named sources  
   within the ``MODS'' directories.  
     
   The order of precedence for this "name-hiding" is as follows:  
   \begin{itemize}  
   \item ``MODS'' directories (in the order given)  
   \item Packages either explicitly specified or provided by default  
     (in the order given)  
   \item Packages included due to package dependencies (in the order  
     that that package dependencies are parsed)  
   \item The "standard dirs" (which may have been specified by the  
     ``-standarddirs'' option)  
   \end{itemize}  
692        
693  \item[\texttt{--make=/path/to/gmake}] Due to the poor handling of  \item[\texttt{--make=/path/to/gmake}] Due to the poor handling of
694    soft-links and other bugs common with the \texttt{make} versions    soft-links and other bugs common with the \texttt{make} versions
695    provided by commercial Unix vendors, GNU \texttt{make} (sometimes    provided by commercial Unix vendors, GNU \texttt{make} (sometimes
696    called \texttt{gmake}) should be preferred.  This option provides a    called \texttt{gmake}) should be preferred.  This option provides a
697    means for specifying the make executable to be used.    means for specifying the make executable to be used.
698      
699    \item[\texttt{--bash=/path/to/sh}] On some (usually older UNIX)
700      machines, the ``bash'' shell is unavailable.  To run on these
701      systems, \texttt{genmake2} can be invoked using an ``sh'' (that is,
702      a Bourne, POSIX, or compatible) shell.  The syntax in these
703      circumstances is:
704      \begin{center}
705        \texttt{\%  /bin/sh genmake2 -bash=/bin/sh [...options...]}
706      \end{center}
707      where \texttt{/bin/sh} can be replaced with the full path and name
708      of the desired shell.
709    
710  \end{description}  \end{description}
711    
712    
713    \subsection{Building with MPI}
714    \label{sec:mpi-build}
715    
716    Building MITgcm to use MPI libraries can be complicated due to the
717    variety of different MPI implementations available, their dependencies
718    or interactions with different compilers, and their often ad-hoc
719    locations within file systems.  For these reasons, its generally a
720    good idea to start by finding and reading the documentation for your
721    machine(s) and, if necessary, seeking help from your local systems
722    administrator.
723    
724    The steps for building MITgcm with MPI support are:
725    \begin{enumerate}
726      
727    \item Determine the locations of your MPI-enabled compiler and/or MPI
728      libraries and put them into an options file as described in Section
729      \ref{sec:genmake}.  One can start with one of the examples in:
730      \begin{rawhtml} <A
731        href="http://mitgcm.org/viewvc/MITgcm/MITgcm/tools/build_options/">
732      \end{rawhtml}
733      \begin{center}
734        \texttt{MITgcm/tools/build\_options/}
735      \end{center}
736      \begin{rawhtml} </A> \end{rawhtml}
737      such as \texttt{linux\_ia32\_g77+mpi\_cg01} or
738      \texttt{linux\_ia64\_efc+mpi} and then edit it to suit the machine at
739      hand.  You may need help from your user guide or local systems
740      administrator to determine the exact location of the MPI libraries.
741      If libraries are not installed, MPI implementations and related
742      tools are available including:
743      \begin{itemize}
744      \item \begin{rawhtml} <A
745          href="http://www-unix.mcs.anl.gov/mpi/mpich/">
746        \end{rawhtml}
747        MPICH
748        \begin{rawhtml} </A> \end{rawhtml}
749    
750      \item \begin{rawhtml} <A
751          href="http://www.lam-mpi.org/">
752        \end{rawhtml}
753        LAM/MPI
754        \begin{rawhtml} </A> \end{rawhtml}
755    
756      \item \begin{rawhtml} <A
757          href="http://www.osc.edu/~pw/mpiexec/">
758        \end{rawhtml}
759        MPIexec
760        \begin{rawhtml} </A> \end{rawhtml}
761      \end{itemize}
762      
763    \item Build the code with the \texttt{genmake2} \texttt{-mpi} option
764      (see Section \ref{sec:genmake}) using commands such as:
765    {\footnotesize \begin{verbatim}
766      %  ../../../tools/genmake2 -mods=../code -mpi -of=YOUR_OPTFILE
767      %  make depend
768      %  make
769    \end{verbatim} }
770      
771    \item Run the code with the appropriate MPI ``run'' or ``exec''
772      program provided with your particular implementation of MPI.
773      Typical MPI packages such as MPICH will use something like:
774    \begin{verbatim}
775      %  mpirun -np 4 -machinefile mf ./mitgcmuv
776    \end{verbatim}
777      Sightly more complicated scripts may be needed for many machines
778      since execution of the code may be controlled by both the MPI
779      library and a job scheduling and queueing system such as PBS,
780      LoadLeveller, Condor, or any of a number of similar tools.  A few
781      example scripts (those used for our \begin{rawhtml} <A
782        href="http://mitgcm.org/public/testing.html"> \end{rawhtml}regular
783      verification runs\begin{rawhtml} </A> \end{rawhtml}) are available
784      at:
785      \begin{rawhtml} <A
786        href="http://mitgcm.org/viewvc/MITgcm/MITgcm/tools/example_scripts/">
787      \end{rawhtml}
788      {\footnotesize \tt
789        http://mitgcm.org/viewvc/MITgcm/MITgcm/tools/example\_scripts/ }
790      \begin{rawhtml} </A> \end{rawhtml}
791      or at:
792      \begin{rawhtml} <A
793        href="http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/test_scripts/">
794      \end{rawhtml}
795      {\footnotesize \tt
796        http://mitgcm.org/viewvc/MITgcm/MITgcm\_contrib/test\_scripts/ }
797      \begin{rawhtml} </A> \end{rawhtml}
798    
799    \end{enumerate}
800    
801  \section{Running the model}  An example of the above process on the MITgcm cluster (``cg01'') using
802  \label{sect:runModel}  the GNU g77 compiler and the mpich MPI library is:
803    
804  If compilation finished succesfuully (section \ref{sect:buildModel})  {\footnotesize \begin{verbatim}
805  then an executable called {\em mitgcmuv} will now exist in the local    %  cd MITgcm/verification/exp5
806  directory.    %  mkdir build
807      %  cd build
808      %  ../../../tools/genmake2 -mpi -mods=../code \
809           -of=../../../tools/build_options/linux_ia32_g77+mpi_cg01
810      %  make depend
811      %  make
812      %  cd ../input
813      %  /usr/local/pkg/mpi/mpi-1.2.4..8a-gm-1.5/g77/bin/mpirun.ch_gm \
814           -machinefile mf --gm-kill 5 -v -np 2  ../build/mitgcmuv
815    \end{verbatim} }
816    
817    \section[Running MITgcm]{Running the model in prognostic mode}
818    \label{sec:runModel}
819    \begin{rawhtml}
820    <!-- CMIREDIR:runModel: -->
821    \end{rawhtml}
822    
823    If compilation finished succesfully (section \ref{sec:buildingCode})
824    then an executable called \texttt{mitgcmuv} will now exist in the
825    local directory.
826    
827  To run the model as a single process (ie. not in parallel) simply  To run the model as a single process (\textit{ie.} not in parallel)
828  type:  simply type:
829  \begin{verbatim}  \begin{verbatim}
830  % ./mitgcmuv  % ./mitgcmuv
831  \end{verbatim}  \end{verbatim}
# Line 814  do!). The above command will spew out ma Line 835  do!). The above command will spew out ma
835  your screen.  This output contains details such as parameter values as  your screen.  This output contains details such as parameter values as
836  well as diagnostics such as mean Kinetic energy, largest CFL number,  well as diagnostics such as mean Kinetic energy, largest CFL number,
837  etc. It is worth keeping this text output with the binary output so we  etc. It is worth keeping this text output with the binary output so we
838  normally re-direct the {\em stdout} stream as follows:  normally re-direct the \texttt{stdout} stream as follows:
839  \begin{verbatim}  \begin{verbatim}
840  % ./mitgcmuv > output.txt  % ./mitgcmuv > output.txt
841  \end{verbatim}  \end{verbatim}
842    In the event that the model encounters an error and stops, it is very
843  For the example experiments in {\em verification}, an example of the  helpful to include the last few line of this \texttt{output.txt} file
844  output is kept in {\em results/output.txt} for comparison. You can compare  along with the (\texttt{stderr}) error message within any bug reports.
845  your {\em output.txt} with this one to check that the set-up works.  
846    For the example experiments in \texttt{verification}, an example of the
847    output is kept in \texttt{results/output.txt} for comparison. You can
848    compare your \texttt{output.txt} with the corresponding one for that
849    experiment to check that the set-up works.
850    
851    
852    
853  \subsection{Output files}  \subsection{Output files}
854    
855  The model produces various output files. At a minimum, the instantaneous  The model produces various output files and, when using \texttt{mnc},
856  ``state'' of the model is written out, which is made of the following files:  sometimes even directories.  Depending upon the I/O package(s)
857    selected at compile time (either \texttt{mdsio} or \texttt{mnc} or
858    both as determined by \texttt{code/packages.conf}) and the run-time
859    flags set (in \texttt{input/data.pkg}), the following output may
860    appear.
861    
862    
863    \subsubsection{MDSIO output files}
864    
865    The ``traditional'' output files are generated by the \texttt{mdsio}
866    package.  At a minimum, the instantaneous ``state'' of the model is
867    written out, which is made of the following files:
868    
869  \begin{itemize}  \begin{itemize}
870  \item \textit{U.00000nIter} - zonal component of velocity field (m/s and $>  \item \texttt{U.00000nIter} - zonal component of velocity field (m/s
871  0 $ eastward).    and positive eastward).
872    
873  \item \textit{V.00000nIter} - meridional component of velocity field (m/s  \item \texttt{V.00000nIter} - meridional component of velocity field
874  and $> 0$ northward).    (m/s and positive northward).
875    
876  \item \textit{W.00000nIter} - vertical component of velocity field (ocean:  \item \texttt{W.00000nIter} - vertical component of velocity field
877  m/s and $> 0$ upward, atmosphere: Pa/s and $> 0$ towards increasing pressure    (ocean: m/s and positive upward, atmosphere: Pa/s and positive
878  i.e. downward).    towards increasing pressure i.e. downward).
879    
880  \item \textit{T.00000nIter} - potential temperature (ocean: $^{0}$C,  \item \texttt{T.00000nIter} - potential temperature (ocean:
881  atmosphere: $^{0}$K).    $^{\circ}\mathrm{C}$, atmosphere: $^{\circ}\mathrm{K}$).
882    
883  \item \textit{S.00000nIter} - ocean: salinity (psu), atmosphere: water vapor  \item \texttt{S.00000nIter} - ocean: salinity (psu), atmosphere: water
884  (g/kg).    vapor (g/kg).
885    
886  \item \textit{Eta.00000nIter} - ocean: surface elevation (m), atmosphere:  \item \texttt{Eta.00000nIter} - ocean: surface elevation (m),
887  surface pressure anomaly (Pa).    atmosphere: surface pressure anomaly (Pa).
888  \end{itemize}  \end{itemize}
889    
890  The chain \textit{00000nIter} consists of ten figures that specify the  The chain \texttt{00000nIter} consists of ten figures that specify the
891  iteration number at which the output is written out. For example, \textit{%  iteration number at which the output is written out. For example,
892  U.0000000300} is the zonal velocity at iteration 300.  \texttt{U.0000000300} is the zonal velocity at iteration 300.
893    
894  In addition, a ``pickup'' or ``checkpoint'' file called:  In addition, a ``pickup'' or ``checkpoint'' file called:
895    
896  \begin{itemize}  \begin{itemize}
897  \item \textit{pickup.00000nIter}  \item \texttt{pickup.00000nIter}
898  \end{itemize}  \end{itemize}
899    
900  is written out. This file represents the state of the model in a condensed  is written out. This file represents the state of the model in a condensed
# Line 866  form and is used for restarting the inte Line 902  form and is used for restarting the inte
902  there is an additional ``pickup'' file:  there is an additional ``pickup'' file:
903    
904  \begin{itemize}  \begin{itemize}
905  \item \textit{pickup\_cd.00000nIter}  \item \texttt{pickup\_cd.00000nIter}
906  \end{itemize}  \end{itemize}
907    
908  containing the D-grid velocity data and that has to be written out as well  containing the D-grid velocity data and that has to be written out as well
909  in order to restart the integration. Rolling checkpoint files are the same  in order to restart the integration. Rolling checkpoint files are the same
910  as the pickup files but are named differently. Their name contain the chain  as the pickup files but are named differently. Their name contain the chain
911  \textit{ckptA} or \textit{ckptB} instead of \textit{00000nIter}. They can be  \texttt{ckptA} or \texttt{ckptB} instead of \texttt{00000nIter}. They can be
912  used to restart the model but are overwritten every other time they are  used to restart the model but are overwritten every other time they are
913  output to save disk space during long integrations.  output to save disk space during long integrations.
914    
915    \subsubsection{MNC output files}
916    
917    Unlike the \texttt{mdsio} output, the \texttt{mnc}--generated output
918    is usually (though not necessarily) placed within a subdirectory with
919    a name such as \texttt{mnc\_test\_\${DATE}\_\${SEQ}}.  
920    
921  \subsection{Looking at the output}  \subsection{Looking at the output}
922    
923  All the model data are written according to a ``meta/data'' file format.  The ``traditional'' or mdsio model data are written according to a
924  Each variable is associated with two files with suffix names \textit{.data}  ``meta/data'' file format.  Each variable is associated with two files
925  and \textit{.meta}. The \textit{.data} file contains the data written in  with suffix names \texttt{.data} and \texttt{.meta}. The
926  binary form (big\_endian by default). The \textit{.meta} file is a  \texttt{.data} file contains the data written in binary form
927  ``header'' file that contains information about the size and the structure  (big\_endian by default). The \texttt{.meta} file is a ``header'' file
928  of the \textit{.data} file. This way of organizing the output is  that contains information about the size and the structure of the
929  particularly useful when running multi-processors calculations. The base  \texttt{.data} file. This way of organizing the output is particularly
930  version of the model includes a few matlab utilities to read output files  useful when running multi-processors calculations. The base version of
931  written in this format. The matlab scripts are located in the directory  the model includes a few matlab utilities to read output files written
932  \textit{utils/matlab} under the root tree. The script \textit{rdmds.m} reads  in this format. The matlab scripts are located in the directory
933  the data. Look at the comments inside the script to see how to use it.  \texttt{utils/matlab} under the root tree. The script \texttt{rdmds.m}
934    reads the data. Look at the comments inside the script to see how to
935    use it.
936    
937  Some examples of reading and visualizing some output in {\em Matlab}:  Some examples of reading and visualizing some output in {\em Matlab}:
938  \begin{verbatim}  \begin{verbatim}
# Line 905  Some examples of reading and visualizing Line 949  Some examples of reading and visualizing
949  >> for n=1:11; imagesc(eta(:,:,n)');axis ij;colorbar;pause(.5);end  >> for n=1:11; imagesc(eta(:,:,n)');axis ij;colorbar;pause(.5);end
950  \end{verbatim}  \end{verbatim}
951    
952  \section{Doing it yourself: customizing the code}  Similar scripts for netCDF output (\texttt{rdmnc.m}) are available and
953    they are described in Section \ref{sec:pkg:mnc}.
 When you are ready to run the model in the configuration you want, the  
 easiest thing is to use and adapt the setup of the case studies  
 experiment (described previously) that is the closest to your  
 configuration. Then, the amount of setup will be minimized. In this  
 section, we focus on the setup relative to the ``numerical model''  
 part of the code (the setup relative to the ``execution environment''  
 part is covered in the parallel implementation section) and on the  
 variables and parameters that you are likely to change.  
   
 \subsection{Configuration and setup}  
   
 The CPP keys relative to the ``numerical model'' part of the code are  
 all defined and set in the file \textit{CPP\_OPTIONS.h }in the  
 directory \textit{ model/inc }or in one of the \textit{code  
 }directories of the case study experiments under  
 \textit{verification.} The model parameters are defined and declared  
 in the file \textit{model/inc/PARAMS.h }and their default values are  
 set in the routine \textit{model/src/set\_defaults.F. }The default  
 values can be modified in the namelist file \textit{data }which needs  
 to be located in the directory where you will run the model. The  
 parameters are initialized in the routine  
 \textit{model/src/ini\_parms.F}.  Look at this routine to see in what  
 part of the namelist the parameters are located.  
   
 In what follows the parameters are grouped into categories related to  
 the computational domain, the equations solved in the model, and the  
 simulation controls.  
   
 \subsection{Computational domain, geometry and time-discretization}  
   
 \begin{description}  
 \item[dimensions] \  
     
   The number of points in the x, y,\textit{\ }and r\textit{\  
   }directions are represented by the variables \textbf{sNx}\textit{,  
   }\textbf{sNy}\textit{, } and \textbf{Nr}\textit{\ }respectively  
   which are declared and set in the file \textit{model/inc/SIZE.h.  
   }(Again, this assumes a mono-processor calculation. For  
   multiprocessor calculations see section on parallel implementation.)  
   
 \item[grid] \  
     
   Three different grids are available: cartesian, spherical polar, and  
   curvilinear (including the cubed sphere). The grid is set through  
   the logical variables \textbf{usingCartesianGrid}\textit{, }\textbf{  
     usingSphericalPolarGrid}\textit{, }and \textit{\ }\textbf{  
     usingCurvilinearGrid}\textit{. }In the case of spherical and  
   curvilinear grids, the southern boundary is defined through the  
   variable \textbf{phiMin} \textit{\ }which corresponds to the  
   latitude of the southern most cell face (in degrees). The resolution  
   along the x and y directions is controlled by the 1D arrays  
   \textbf{delx}\textit{\ }and \textbf{dely}\textit{\ }(in meters in  
   the case of a cartesian grid, in degrees otherwise). The vertical  
   grid spacing is set through the 1D array \textbf{delz }for the ocean  
   (in meters) or \textbf{delp}\textit{\ }for the atmosphere (in Pa).  
   The variable \textbf{ Ro\_SeaLevel} represents the standard position  
   of Sea-Level in ''R'' coordinate. This is typically set to 0m for  
   the ocean (default value) and 10$ ^{5}$Pa for the atmosphere. For  
   the atmosphere, also set the logical variable \textbf{groundAtK1} to  
   '.\texttt{TRUE}.'. which put the first level (k=1) at the lower  
   boundary (ground).  
     
   For the cartesian grid case, the Coriolis parameter $f$ is set  
   through the variables \textbf{f0}\textit{\ }and  
   \textbf{beta}\textit{\ }which correspond to the reference Coriolis  
   parameter (in s$^{-1}$) and $\frac{\partial f}{ \partial y}$(in  
   m$^{-1}$s$^{-1}$) respectively. If \textbf{beta }\textit{\ } is set  
   to a nonzero value, \textbf{f0}\textit{\ }is the value of $f$ at the  
   southern edge of the domain.  
   
 \item[topography - full and partial cells] \  
     
   The domain bathymetry is read from a file that contains a 2D (x,y)  
   map of depths (in m) for the ocean or pressures (in Pa) for the  
   atmosphere. The file name is represented by the variable  
   \textbf{bathyFile}\textit{. }The file is assumed to contain binary  
   numbers giving the depth (pressure) 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  
   model code applies without modification to enclosed, periodic, and  
   double periodic domains. Periodicity is assumed by default and is  
   suppressed by setting the depths to 0m for the cells at the limits  
   of the computational domain (note: not sure this is the case for the  
   atmosphere). The precision with which to read the binary data is  
   controlled by the integer variable \textbf{readBinaryPrec }which can  
   take the value \texttt{32} (single precision) or \texttt{64} (double  
   precision). See the matlab program \textit{ gendata.m }in the  
   \textit{input }directories under \textit{verification }to see how  
   the bathymetry files are generated for the case study experiments.  
     
   To use the partial cell capability, the variable  
   \textbf{hFacMin}\textit{\ } needs to be set to a value between 0 and  
   1 (it is set to 1 by default) corresponding to the minimum  
   fractional size of the cell. For example if the bottom cell is 500m  
   thick and \textbf{hFacMin}\textit{\ }is set to 0.1, the actual  
   thickness of the cell (i.e. used in the code) can cover a range of  
   discrete values 50m apart from 50m to 500m depending on the value of  
   the bottom depth (in \textbf{bathyFile}) at this point.  
     
   Note that the bottom depths (or pressures) need not coincide with  
   the models levels as deduced from \textbf{delz}\textit{\  
   }or\textit{\ }\textbf{delp} \textit{. }The model will interpolate  
   the numbers in \textbf{bathyFile} \textit{\ }so that they match the  
   levels obtained from \textbf{delz}\textit{ \ }or\textit{\  
   }\textbf{delp}\textit{\ }and \textbf{hFacMin}\textit{. }  
     
   (Note: the atmospheric case is a bit more complicated than what is  
   written here I think. To come soon...)  
   
 \item[time-discretization] \  
     
   The time steps are set through the real variables \textbf{deltaTMom}  
   and \textbf{deltaTtracer} (in s) which represent the time step for  
   the momentum and tracer equations, respectively. For synchronous  
   integrations, simply set the two variables to the same value (or you  
   can prescribe one time step only through the variable  
   \textbf{deltaT}). The Adams-Bashforth stabilizing parameter is set  
   through the variable \textbf{abEps} (dimensionless). The stagger  
   baroclinic time stepping can be activated by setting the logical  
   variable \textbf{staggerTimeStep} to '.\texttt{TRUE}.'.  
   
 \end{description}  
   
   
 \subsection{Equation of state}  
   
 First, because the model equations are written in terms of  
 perturbations, a reference thermodynamic state needs to be specified.  
 This is done through the 1D arrays \textbf{tRef} and \textbf{sRef}.  
 \textbf{tRef} specifies the reference potential temperature profile  
 (in $^{o}$C for the ocean and $^{o}$K for the atmosphere) starting  
 from the level k=1. Similarly, \textbf{sRef} specifies the reference  
 salinity profile (in ppt) for the ocean or the reference specific  
 humidity profile (in g/kg) for the atmosphere.  
   
 The form of the equation of state is controlled by the character  
 variables \textbf{buoyancyRelation} and \textbf{eosType}.  
 \textbf{buoyancyRelation} is set to '\texttt{OCEANIC}' by default and  
 needs to be set to '\texttt{ATMOSPHERIC}' for atmosphere simulations.  
 In this case, \textbf{eosType} must be set to '\texttt{IDEALGAS}'.  
 For the ocean, two forms of the equation of state are available:  
 linear (set \textbf{eosType} to '\texttt{LINEAR}') and a polynomial  
 approximation to the full nonlinear equation ( set  
 \textbf{eosType}\textit{\ }to '\texttt{POLYNOMIAL}'). In the linear  
 case, you need to specify the thermal and haline expansion  
 coefficients represented by the variables \textbf{tAlpha}\textit{\  
   }(in K$^{-1}$) and \textbf{sBeta} (in ppt$^{-1}$). For the nonlinear  
 case, you need to generate a file of polynomial coefficients called  
 \textit{POLY3.COEFFS}. To do this, use the program  
 \textit{utils/knudsen2/knudsen2.f} under the model tree (a Makefile is  
 available in the same directory and you will need to edit the number  
 and the values of the vertical levels in \textit{knudsen2.f} so that  
 they match those of your configuration).  
   
 There there are also higher polynomials for the equation of state:  
 \begin{description}  
 \item['\texttt{UNESCO}':] The UNESCO equation of state formula of  
   Fofonoff and Millard \cite{fofonoff83}. This equation of state  
   assumes in-situ temperature, which is not a model variable; \emph{its use  
   is therefore discouraged, and it is only listed for completeness}.  
 \item['\texttt{JMD95Z}':] A modified UNESCO formula by Jackett and  
   McDougall \cite{jackett95}, which uses the model variable potential  
   temperature as input. The '\texttt{Z}' indicates that this equation  
   of state uses a horizontally and temporally constant pressure  
   $p_{0}=-g\rho_{0}z$.  
 \item['\texttt{JMD95P}':] A modified UNESCO formula by Jackett and  
   McDougall \cite{jackett95}, which uses the model variable potential  
   temperature as input. The '\texttt{P}' indicates that this equation  
   of state uses the actual hydrostatic pressure of the last time  
   step. Lagging the pressure in this way requires an additional pickup  
   file for restarts.  
 \item['\texttt{MDJWF}':] The new, more accurate and less expensive  
   equation of state by McDougall et~al. \cite{mcdougall03}. It also  
   requires lagging the pressure and therefore an additional pickup  
   file for restarts.  
 \end{description}  
 For none of these options an reference profile of temperature or  
 salinity is required.  
   
 \subsection{Momentum equations}  
954    
955  In this section, we only focus for now on the parameters that you are likely  The MNC output files are all in the ``self-describing'' netCDF
956  to change, i.e. the ones relative to forcing and dissipation for example.  format and can thus be browsed and/or plotted using tools such as:
957  The details relevant to the vector-invariant form of the equations and the  \begin{itemize}
958  various advection schemes are not covered for the moment. We assume that you  \item \texttt{ncdump} is a utility which is typically included
959  use the standard form of the momentum equations (i.e. the flux-form) with    with every netCDF install:
960  the default advection scheme. Also, there are a few logical variables that    \begin{rawhtml} <A href="http://www.unidata.ucar.edu/packages/netcdf/"> \end{rawhtml}
961  allow you to turn on/off various terms in the momentum equation. These  \begin{verbatim}
962  variables are called \textbf{momViscosity, momAdvection, momForcing,  http://www.unidata.ucar.edu/packages/netcdf/
963  useCoriolis, momPressureForcing, momStepping}\textit{, }and \textit{\ }%  \end{verbatim}
964  \textbf{metricTerms }and are assumed to be set to '.\texttt{TRUE}.' here.    \begin{rawhtml} </A> \end{rawhtml} and it converts the netCDF
965  Look at the file \textit{model/inc/PARAMS.h }for a precise definition of    binaries into formatted ASCII text files.
 these variables.  
   
 \begin{description}  
 \item[initialization] \  
     
   The velocity components are initialized to 0 unless the simulation  
   is starting from a pickup file (see section on simulation control  
   parameters).  
   
 \item[forcing] \  
     
   This section only applies to the ocean. You need to generate  
   wind-stress data into two files \textbf{zonalWindFile}\textit{\ }and  
   \textbf{ meridWindFile }corresponding to the zonal and meridional  
   components of the wind stress, respectively (if you want the stress  
   to be along the direction of only one of the model horizontal axes,  
   you only need to generate one file). The format of the files is  
   similar to the bathymetry file. The zonal (meridional) stress data  
   are assumed to be in Pa and located at U-points (V-points). As for  
   the bathymetry, the precision with which to read the binary data is  
   controlled by the variable \textbf{readBinaryPrec}.\textbf{\ } See  
   the matlab program \textit{gendata.m }in the \textit{input  
   }directories under \textit{verification }to see how simple  
   analytical wind forcing data are generated for the case study  
   experiments.  
     
   There is also the possibility of prescribing time-dependent periodic  
   forcing. To do this, concatenate the successive time records into a  
   single file (for each stress component) ordered in a (x, y, t)  
   fashion and set the following variables:  
   \textbf{periodicExternalForcing }to '.\texttt{TRUE}.',  
   \textbf{externForcingPeriod }to the period (in s) of which the  
   forcing varies (typically 1 month), and \textbf{externForcingCycle  
   }to the repeat time (in s) of the forcing (typically 1 year -- note:  
   \textbf{ externForcingCycle }must be a multiple of  
   \textbf{externForcingPeriod}).  With these variables set up, the  
   model will interpolate the forcing linearly at each iteration.  
   
 \item[dissipation] \  
     
   The lateral eddy viscosity coefficient is specified through the  
   variable \textbf{viscAh}\textit{\ }(in m$^{2}$s$^{-1}$). The  
   vertical eddy viscosity coefficient is specified through the  
   variable \textbf{viscAz }(in m$^{2}$s$ ^{-1}$) for the ocean and  
   \textbf{viscAp}\textit{\ }(in Pa$^{2}$s$^{-1}$) for the atmosphere.  
   The vertical diffusive fluxes can be computed implicitly by setting  
   the logical variable \textbf{implicitViscosity }to '.\texttt{TRUE}  
   .'. In addition, biharmonic mixing can be added as well through the  
   variable \textbf{viscA4}\textit{\ }(in m$^{4}$s$^{-1}$). On a  
   spherical polar grid, you might also need to set the variable  
   \textbf{cosPower} which is set to 0 by default and which represents  
   the power of cosine of latitude to multiply viscosity. Slip or  
   no-slip conditions at lateral and bottom boundaries are specified  
   through the logical variables \textbf{no\_slip\_sides}\textit{\ }  
   and \textbf{no\_slip\_bottom}. If set to '\texttt{.FALSE.}',  
   free-slip boundary conditions are applied. If no-slip boundary  
   conditions are applied at the bottom, a bottom drag can be applied  
   as well. Two forms are available: linear (set the variable  
   \textbf{bottomDragLinear}\textit{\ }in s$ ^{-1}$) and quadratic (set  
   the variable \textbf{bottomDragQuadratic}\textit{ \ }in m$^{-1}$).  
   
   The Fourier and Shapiro filters are described elsewhere.  
   
 \item[C-D scheme] \  
     
   If you run at a sufficiently coarse resolution, you will need the  
   C-D scheme for the computation of the Coriolis terms. The  
   variable\textbf{\ tauCD}, which represents the C-D scheme coupling  
   timescale (in s) needs to be set.  
     
 \item[calculation of pressure/geopotential] \  
     
   First, to run a non-hydrostatic ocean simulation, set the logical  
   variable \textbf{nonHydrostatic} to '.\texttt{TRUE}.'. The pressure  
   field is then inverted through a 3D elliptic equation. (Note: this  
   capability is not available for the atmosphere yet.) By default, a  
   hydrostatic simulation is assumed and a 2D elliptic equation is used  
   to invert the pressure field. The parameters controlling the  
   behaviour of the elliptic solvers are the variables  
   \textbf{cg2dMaxIters}\textit{\ }and \textbf{cg2dTargetResidual } for  
   the 2D case and \textbf{cg3dMaxIters}\textit{\ }and \textbf{  
     cg3dTargetResidual }for the 3D case. You probably won't need to  
   alter the default values (are we sure of this?).  
     
   For the calculation of the surface pressure (for the ocean) or  
   surface geopotential (for the atmosphere) you need to set the  
   logical variables \textbf{rigidLid} and  
   \textbf{implicitFreeSurface}\textit{\ }(set one to '.  
   \texttt{TRUE}.' and the other to '.\texttt{FALSE}.' depending on how  
   you want to deal with the ocean upper or atmosphere lower boundary).  
   
 \end{description}  
   
 \subsection{Tracer equations}  
   
 This section covers the tracer equations i.e. the potential temperature  
 equation and the salinity (for the ocean) or specific humidity (for the  
 atmosphere) equation. As for the momentum equations, we only describe for  
 now the parameters that you are likely to change. The logical variables  
 \textbf{tempDiffusion}\textit{, }\textbf{tempAdvection}\textit{, }\textbf{  
 tempForcing}\textit{,} and \textbf{tempStepping} allow you to turn on/off  
 terms in the temperature equation (same thing for salinity or specific  
 humidity with variables \textbf{saltDiffusion}\textit{, }\textbf{  
 saltAdvection}\textit{\ }etc). These variables are all assumed here to be  
 set to '.\texttt{TRUE}.'. Look at file \textit{model/inc/PARAMS.h }for a  
 precise definition.  
   
 \begin{description}  
 \item[initialization] \  
     
   The initial tracer data can be contained in the binary files  
   \textbf{ hydrogThetaFile }and \textbf{hydrogSaltFile}. These files  
   should contain 3D data ordered in an (x, y, r) fashion with k=1 as  
   the first vertical level.  If no file names are provided, the  
   tracers are then initialized with the values of \textbf{tRef }and  
   \textbf{sRef }mentioned above (in the equation of state section). In  
   this case, the initial tracer data are uniform in x and y for each  
   depth level.  
   
 \item[forcing] \  
     
   This part is more relevant for the ocean, the procedure for the  
   atmosphere not being completely stabilized at the moment.  
     
   A combination of fluxes data and relaxation terms can be used for  
   driving the tracer equations. \ For potential temperature, heat flux  
   data (in W/m$ ^{2}$) can be stored in the 2D binary file  
   \textbf{surfQfile}\textit{. }  Alternatively or in addition, the  
   forcing can be specified through a relaxation term. The SST data to  
   which the model surface temperatures are restored to are supposed to  
   be stored in the 2D binary file \textbf{ thetaClimFile}\textit{.  
   }The corresponding relaxation time scale coefficient is set through  
   the variable \textbf{tauThetaClimRelax}\textit{\ }(in s). The same  
   procedure applies for salinity with the variable names  
   \textbf{EmPmRfile }\textit{, }\textbf{saltClimFile}\textit{, }and  
   \textbf{tauSaltClimRelax} \textit{\ }for freshwater flux (in m/s)  
   and surface salinity (in ppt) data files and relaxation time scale  
   coefficient (in s), respectively. Also for salinity, if the CPP key  
   \textbf{USE\_NATURAL\_BCS} is turned on, natural boundary conditions  
   are applied i.e. when computing the surface salinity tendency, the  
   freshwater flux is multiplied by the model surface salinity instead  
   of a constant salinity value.  
     
   As for the other input files, the precision with which to read the  
   data is controlled by the variable \textbf{readBinaryPrec}.  
   Time-dependent, periodic forcing can be applied as well following  
   the same procedure used for the wind forcing data (see above).  
   
 \item[dissipation] \  
     
   Lateral eddy diffusivities for temperature and salinity/specific  
   humidity are specified through the variables \textbf{diffKhT }and  
   \textbf{diffKhS } (in m$^{2}$/s). Vertical eddy diffusivities are  
   specified through the variables \textbf{diffKzT }and \textbf{diffKzS  
   }(in m$^{2}$/s) for the ocean and \textbf{diffKpT }and  
   \textbf{diffKpS }(in Pa$^{2}$/s) for the atmosphere. The vertical  
   diffusive fluxes can be computed implicitly by setting the logical  
   variable \textbf{implicitDiffusion }to '.\texttt{TRUE} .'. In  
   addition, biharmonic diffusivities can be specified as well through  
   the coefficients \textbf{diffK4T }and \textbf{diffK4S }(in  
   m$^{4}$/s). Note that the cosine power scaling (specified through  
   \textbf{cosPower }- see the momentum equations section) is applied  
   to the tracer diffusivities (Laplacian and biharmonic) as well. The  
   Gent and McWilliams parameterization for oceanic tracers is  
   described in the package section. Finally, note that tracers can be  
   also subject to Fourier and Shapiro filtering (see the corresponding  
   section on these filters).  
   
 \item[ocean convection] \  
     
   Two options are available to parameterize ocean convection: one is  
   to use the convective adjustment scheme. In this case, you need to  
   set the variable \textbf{cadjFreq}, which represents the frequency  
   (in s) with which the adjustment algorithm is called, to a non-zero  
   value (if set to a negative value by the user, the model will set it  
   to the tracer time step). The other option is to parameterize  
   convection with implicit vertical diffusion. To do this, set the  
   logical variable \textbf{implicitDiffusion }to '.\texttt{TRUE} .'  
   and the real variable \textbf{ivdc\_kappa }to a value (in m$^{2}$/s)  
   you wish the tracer vertical diffusivities to have when mixing  
   tracers vertically due to static instabilities. Note that  
   \textbf{cadjFreq }and \textbf{ivdc\_kappa }can not both have  
   non-zero value.  
   
 \end{description}  
   
 \subsection{Simulation controls}  
   
 The model ''clock'' is defined by the variable \textbf{deltaTClock }(in s)  
 which determines the IO frequencies and is used in tagging output.  
 Typically, you will set it to the tracer time step for accelerated runs  
 (otherwise it is simply set to the default time step \textbf{deltaT}).  
 Frequency of checkpointing and dumping of the model state are referenced to  
 this clock (see below).  
966    
967  \begin{description}  \item \texttt{ncview} utility is a very convenient and quick way
968  \item[run duration] \    to plot netCDF data and it runs on most OSes:
969      \begin{rawhtml} <A href="http://meteora.ucsd.edu/~pierce/ncview_home_page.html"> \end{rawhtml}
970    \begin{verbatim}
971    http://meteora.ucsd.edu/~pierce/ncview_home_page.html
972    \end{verbatim}
973      \begin{rawhtml} </A> \end{rawhtml}
974        
975    The beginning of a simulation is set by specifying a start time (in  \item MatLAB(c) and other common post-processing environments provide
976    s) through the real variable \textbf{startTime }or by specifying an    various netCDF interfaces including:
977    initial iteration number through the integer variable    \begin{rawhtml} <A href="http://mexcdf.sourceforge.net/"> \end{rawhtml}
978    \textbf{nIter0}. If these variables are set to nonzero values, the  \begin{verbatim}
979    model will look for a ''pickup'' file \textit{pickup.0000nIter0 }to  http://mexcdf.sourceforge.net/
980    restart the integration\textit{. }The end of a simulation is set  \end{verbatim}
981    through the real variable \textbf{endTime }(in s).  Alternatively,    \begin{rawhtml} </A> \end{rawhtml}
982    you can specify instead the number of time steps to execute through    \begin{rawhtml} <A href="http://woodshole.er.usgs.gov/staffpages/cdenham/public_html/MexCDF/nc4ml5.html"> \end{rawhtml}
983    the integer variable \textbf{nTimeSteps}.  \begin{verbatim}
984    http://woodshole.er.usgs.gov/staffpages/cdenham/public_html/MexCDF/nc4ml5.html
985  \item[frequency of output] \  \end{verbatim}
986        \begin{rawhtml} </A> \end{rawhtml}
987    Real variables defining frequencies (in s) with which output files  \end{itemize}
   are written on disk need to be set up. \textbf{dumpFreq }controls  
   the frequency with which the instantaneous state of the model is  
   saved. \textbf{chkPtFreq } and \textbf{pchkPtFreq }control the  
   output frequency of rolling and permanent checkpoint files,  
   respectively. See section 1.5.1 Output files for the definition of  
   model state and checkpoint files. In addition, time-averaged fields  
   can be written out by setting the variable \textbf{taveFreq} (in s).  
   The precision with which to write the binary data is controlled by  
   the integer variable w\textbf{riteBinaryPrec }(set it to \texttt{32}  
   or \texttt{ 64}).  
   
 \end{description}  
   
988    
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