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% $Header: /u/u3/gcmpack/manual/part3/getting_started.tex,v 1.14 2003/07/30 13:42:52 edhill Exp $ |
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% $Name: $ |
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|
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%\section{Getting started} |
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|
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In this section, we describe how to use the model. In the first |
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section, we provide enough information to help you get started with |
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the model. We believe the best way to familiarize yourself with the |
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model is to run the case study examples provided with the base |
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version. Information on how to obtain, compile, and run the code is |
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found there as well as a brief description of the model structure |
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directory and the case study examples. The latter and the code |
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structure are described more fully in chapters |
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\ref{chap:discretization} and \ref{chap:sarch}, respectively. Here, in |
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this section, we provide information on how to customize the code when |
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you are ready to try implementing the configuration you have in mind. |
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|
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\section{Where to find information} |
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\label{sect:whereToFindInfo} |
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|
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A web site is maintained for release 2 (``Pelican'') of MITgcm: |
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\begin{rawhtml} <A href=http://mitgcm.org/pelican/ target="idontexist"> \end{rawhtml} |
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\begin{verbatim} |
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http://mitgcm.org/pelican |
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\end{verbatim} |
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\begin{rawhtml} </A> \end{rawhtml} |
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Here you will find an on-line version of this document, a |
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``browsable'' copy of the code and a searchable database of the model |
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and site, as well as links for downloading the model and |
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documentation, to data-sources, and other related sites. |
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|
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There is also a web-archived support mailing list for the model that |
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you can email at \texttt{MITgcm-support@mitgcm.org} or browse at: |
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\begin{rawhtml} <A href=http://mitgcm.org/mailman/listinfo/mitgcm-support/ target="idontexist"> \end{rawhtml} |
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\begin{verbatim} |
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http://mitgcm.org/mailman/listinfo/mitgcm-support/ |
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http://mitgcm.org/pipermail/mitgcm-support/ |
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\end{verbatim} |
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\begin{rawhtml} </A> \end{rawhtml} |
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Essentially all of the MITgcm web pages can be searched using a |
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popular web crawler such as Google or through our own search facility: |
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\begin{verbatim} |
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http://mitgcm.org/htdig/ |
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\end{verbatim} |
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\begin{rawhtml} </A> \end{rawhtml} |
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%%% http://www.google.com/search?q=hydrostatic+site%3Amitgcm.org |
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|
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|
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|
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\section{Obtaining the code} |
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\label{sect:obtainingCode} |
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|
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MITgcm can be downloaded from our system by following |
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the instructions below. As a courtesy we ask that you send e-mail to us at |
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\begin{rawhtml} <A href=mailto:MITgcm-support@mitgcm.org> \end{rawhtml} |
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MITgcm-support@mitgcm.org |
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\begin{rawhtml} </A> \end{rawhtml} |
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to enable us to keep track of who's using the model and in what application. |
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You can download the model two ways: |
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|
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\begin{enumerate} |
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\item Using CVS software. CVS is a freely available source code management |
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tool. To use CVS you need to have the software installed. Many systems |
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come with CVS pre-installed, otherwise good places to look for |
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the software for a particular platform are |
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\begin{rawhtml} <A href=http://www.cvshome.org/ target="idontexist"> \end{rawhtml} |
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cvshome.org |
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\begin{rawhtml} </A> \end{rawhtml} |
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and |
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\begin{rawhtml} <A href=http://www.wincvs.org/ target="idontexist"> \end{rawhtml} |
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wincvs.org |
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\begin{rawhtml} </A> \end{rawhtml} |
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. |
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|
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\item Using a tar file. This method is simple and does not |
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require any special software. However, this method does not |
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provide easy support for maintenance updates. |
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|
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\end{enumerate} |
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|
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If CVS is available on your system, we strongly encourage you to use it. CVS |
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provides an efficient and elegant way of organizing your code and keeping |
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track of your changes. If CVS is not available on your machine, you can also |
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download a tar file. |
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|
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Before you can use CVS, the following environment variable(s) should |
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be set within your shell. For a csh or tcsh shell, put the following |
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\begin{verbatim} |
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% setenv CVSROOT :pserver:cvsanon@mitgcm.org:/u/gcmpack |
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\end{verbatim} |
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in your .cshrc or .tcshrc file. For bash or sh shells, put: |
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\begin{verbatim} |
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% export CVSROOT=':pserver:cvsanon@mitgcm.org:/u/gcmpack' |
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\end{verbatim} |
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in your .profile or .bashrc file. |
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|
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|
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To get MITgcm through CVS, first register with the MITgcm CVS server |
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using command: |
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\begin{verbatim} |
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% cvs login ( CVS password: cvsanon ) |
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\end{verbatim} |
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You only need to do a ``cvs login'' once. |
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|
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To obtain the latest sources type: |
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\begin{verbatim} |
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% cvs co MITgcm |
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\end{verbatim} |
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or to get a specific release type: |
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\begin{verbatim} |
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% cvs co -d directory -P -r release1_beta1 MITgcm |
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\end{verbatim} |
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The MITgcm web site contains further directions concerning the source |
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code and CVS. It also contains a web interface to our CVS archive so |
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that one may easily view the state of files, revisions, and other |
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development milestones: |
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\begin{rawhtml} <A href=http://mitgcm.org/download target="idontexist"> \end{rawhtml} |
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\begin{verbatim} |
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http://mitgcm.org/source_code.html |
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\end{verbatim} |
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\begin{rawhtml} </A> \end{rawhtml} |
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|
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|
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The checkout process creates a directory called \textit{MITgcm}. If |
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the directory \textit{MITgcm} exists this command updates your code |
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based on the repository. Each directory in the source tree contains a |
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directory \textit{CVS}. This information is required by CVS to keep |
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track of your file versions with respect to the repository. Don't edit |
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the files in \textit{CVS}! You can also use CVS to download code |
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updates. More extensive information on using CVS for maintaining |
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MITgcm code can be found |
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\begin{rawhtml} <A href=http://mitgcm.org/usingcvstoget.html target="idontexist"> \end{rawhtml} |
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here |
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\begin{rawhtml} </A> \end{rawhtml} |
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. |
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|
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|
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\paragraph*{Conventional download method} |
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\label{sect:conventionalDownload} |
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|
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If you do not have CVS on your system, you can download the model as a |
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tar file from the web site at: |
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\begin{rawhtml} <A href=http://mitgcm.org/download target="idontexist"> \end{rawhtml} |
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\begin{verbatim} |
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http://mitgcm.org/download/ |
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\end{verbatim} |
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\begin{rawhtml} </A> \end{rawhtml} |
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The tar file still contains CVS information which we urge you not to |
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delete; even if you do not use CVS yourself the information can help |
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us if you should need to send us your copy of the code. If a recent |
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tar file does not exist, then please contact the developers through |
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the MITgcm-support list. |
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|
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\paragraph*{Upgrading from an earlier version} |
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|
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If you already have an earlier version of the code you can ``upgrade'' |
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your copy instead of downloading the entire repository again. First, |
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``cd'' (change directory) to the top of your working copy: |
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\begin{verbatim} |
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% cd MITgcm |
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\end{verbatim} |
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and then issue the cvs update command such as: |
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\begin{verbatim} |
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% cvs -q update -r release1_beta1 -d -P |
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\end{verbatim} |
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This will update the ``tag'' to ``release1\_beta1'', add any new |
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directories (-d) and remove any empty directories (-P). The -q option |
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means be quiet which will reduce the number of messages you'll see in |
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the terminal. If you have modified the code prior to upgrading, CVS |
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will try to merge your changes with the upgrades. If there is a |
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conflict between your modifications and the upgrade, it will report |
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that file with a ``C'' in front, e.g.: |
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\begin{verbatim} |
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C model/src/ini_parms.F |
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\end{verbatim} |
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If the list of conflicts scrolled off the screen, you can re-issue the |
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cvs update command and it will report the conflicts. Conflicts are |
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indicated in the code by the delimites ``$<<<<<<<$'', ``======='' and |
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``$>>>>>>>$''. For example, |
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\begin{verbatim} |
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<<<<<<< ini_parms.F |
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& bottomDragLinear,myOwnBottomDragCoefficient, |
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======= |
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& bottomDragLinear,bottomDragQuadratic, |
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>>>>>>> 1.18 |
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\end{verbatim} |
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means that you added ``myOwnBottomDragCoefficient'' to a namelist at |
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the same time and place that we added ``bottomDragQuadratic''. You |
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need to resolve this conflict and in this case the line should be |
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changed to: |
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\begin{verbatim} |
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& bottomDragLinear,bottomDragQuadratic,myOwnBottomDragCoefficient, |
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\end{verbatim} |
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and the lines with the delimiters ($<<<<<<$,======,$>>>>>>$) be deleted. |
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Unless you are making modifications which exactly parallel |
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developments we make, these types of conflicts should be rare. |
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|
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\paragraph*{Upgrading to the current pre-release version} |
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|
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We don't make a ``release'' for every little patch and bug fix in |
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order to keep the frequency of upgrades to a minimum. However, if you |
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have run into a problem for which ``we have already fixed in the |
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latest code'' and we haven't made a ``tag'' or ``release'' since that |
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patch then you'll need to get the latest code: |
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\begin{verbatim} |
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% cvs -q update -A -d -P |
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\end{verbatim} |
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Unlike, the ``check-out'' and ``update'' procedures above, there is no |
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``tag'' or release name. The -A tells CVS to upgrade to the |
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very latest version. As a rule, we don't recommend this since you |
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might upgrade while we are in the processes of checking in the code so |
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that you may only have part of a patch. Using this method of updating |
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also means we can't tell what version of the code you are working |
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with. So please be sure you understand what you're doing. |
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|
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\section{Model and directory structure} |
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|
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The ``numerical'' model is contained within a execution environment |
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support wrapper. This wrapper is designed to provide a general |
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framework for grid-point models. MITgcmUV is a specific numerical |
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model that uses the framework. Under this structure the model is split |
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into execution environment support code and conventional numerical |
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model code. The execution environment support code is held under the |
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\textit{eesupp} directory. The grid point model code is held under the |
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\textit{model} directory. Code execution actually starts in the |
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\textit{eesupp} routines and not in the \textit{model} routines. For |
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this reason the top-level |
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\textit{MAIN.F} is in the \textit{eesupp/src} directory. In general, |
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end-users should not need to worry about this level. The top-level routine |
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for the numerical part of the code is in \textit{model/src/THE\_MODEL\_MAIN.F% |
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}. Here is a brief description of the directory structure of the model under |
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the root tree (a detailed description is given in section 3: Code structure). |
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|
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\begin{itemize} |
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\item \textit{bin}: this directory is initially empty. It is the default |
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directory in which to compile the code. |
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|
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\item \textit{diags}: contains the code relative to time-averaged |
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diagnostics. It is subdivided into two subdirectories \textit{inc} and |
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\textit{src} that contain include files (*.\textit{h} files) and Fortran |
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subroutines (*.\textit{F} files), respectively. |
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|
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\item \textit{doc}: contains brief documentation notes. |
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|
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\item \textit{eesupp}: contains the execution environment source code. Also |
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subdivided into two subdirectories \textit{inc} and \textit{src}. |
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|
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\item \textit{exe}: this directory is initially empty. It is the default |
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directory in which to execute the code. |
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|
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\item \textit{model}: this directory contains the main source code. Also |
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subdivided into two subdirectories \textit{inc} and \textit{src}. |
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|
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\item \textit{pkg}: contains the source code for the packages. Each package |
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corresponds to a subdirectory. For example, \textit{gmredi} contains the |
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code related to the Gent-McWilliams/Redi scheme, \textit{aim} the code |
| 257 |
relative to the atmospheric intermediate physics. The packages are described |
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in detail in section 3. |
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|
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\item \textit{tools}: this directory contains various useful tools. For |
| 261 |
example, \textit{genmake2} is a script written in csh (C-shell) that should |
| 262 |
be used to generate your makefile. The directory \textit{adjoint} contains |
| 263 |
the makefile specific to the Tangent linear and Adjoint Compiler (TAMC) that |
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generates the adjoint code. The latter is described in details in part V. |
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|
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\item \textit{utils}: this directory contains various utilities. The |
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subdirectory \textit{knudsen2} contains code and a makefile that |
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compute coefficients of the polynomial approximation to the knudsen |
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formula for an ocean nonlinear equation of state. The \textit{matlab} |
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subdirectory contains matlab scripts for reading model output directly |
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into matlab. \textit{scripts} contains C-shell post-processing |
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scripts for joining processor-based and tiled-based model output. |
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|
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\item \textit{verification}: this directory contains the model examples. See |
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section \ref{sect:modelExamples}. |
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\end{itemize} |
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|
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\section{Example experiments} |
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\label{sect:modelExamples} |
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|
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%% a set of twenty-four pre-configured numerical experiments |
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|
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The MITgcm distribution comes with more than a dozen pre-configured |
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numerical experiments. Some of these example experiments are tests of |
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individual parts of the model code, but many are fully fledged |
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numerical simulations. A few of the examples are used for tutorial |
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documentation in sections \ref{sect:eg-baro} - \ref{sect:eg-global}. |
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The other examples follow the same general structure as the tutorial |
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examples. However, they only include brief instructions in a text file |
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called {\it README}. The examples are located in subdirectories under |
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the directory \textit{verification}. Each example is briefly described |
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below. |
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|
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\subsection{Full list of model examples} |
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|
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\begin{enumerate} |
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\item \textit{exp0} - single layer, ocean double gyre (barotropic with |
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free-surface). This experiment is described in detail in section |
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\ref{sect:eg-baro}. |
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|
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\item \textit{exp1} - Four layer, ocean double gyre. This experiment |
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is described in detail in section \ref{sect:eg-baroc}. |
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|
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\item \textit{exp2} - 4x4 degree global ocean simulation with steady |
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climatological forcing. This experiment is described in detail in |
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section \ref{sect:eg-global}. |
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|
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\item \textit{exp4} - Flow over a Gaussian bump in open-water or |
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channel with open boundaries. |
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|
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\item \textit{exp5} - Inhomogenously forced ocean convection in a |
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doubly periodic box. |
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|
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\item \textit{front\_relax} - Relaxation of an ocean thermal front (test for |
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Gent/McWilliams scheme). 2D (Y-Z). |
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|
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\item \textit{internal wave} - Ocean internal wave forced by open |
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boundary conditions. |
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|
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\item \textit{natl\_box} - Eastern subtropical North Atlantic with KPP |
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scheme; 1 month integration |
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|
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\item \textit{hs94.1x64x5} - Zonal averaged atmosphere using Held and |
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Suarez '94 forcing. |
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|
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\item \textit{hs94.128x64x5} - 3D atmosphere dynamics using Held and |
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Suarez '94 forcing. |
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|
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\item \textit{hs94.cs-32x32x5} - 3D atmosphere dynamics using Held and |
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Suarez '94 forcing on the cubed sphere. |
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|
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\item \textit{aim.5l\_zon-ave} - Intermediate Atmospheric physics. |
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Global Zonal Mean configuration, 1x64x5 resolution. |
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|
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\item \textit{aim.5l\_XZ\_Equatorial\_Slice} - Intermediate |
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Atmospheric physics, equatorial Slice configuration. 2D (X-Z). |
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|
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\item \textit{aim.5l\_Equatorial\_Channel} - Intermediate Atmospheric |
| 339 |
physics. 3D Equatorial Channel configuration. |
| 340 |
|
| 341 |
\item \textit{aim.5l\_LatLon} - Intermediate Atmospheric physics. |
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Global configuration, on latitude longitude grid with 128x64x5 grid |
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points ($2.8^\circ{\rm degree}$ resolution). |
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|
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\item \textit{adjustment.128x64x1} Barotropic adjustment problem on |
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latitude longitude grid with 128x64 grid points ($2.8^\circ{\rm |
| 347 |
degree}$ resolution). |
| 348 |
|
| 349 |
\item \textit{adjustment.cs-32x32x1} Barotropic adjustment problem on |
| 350 |
cube sphere grid with 32x32 points per face ( roughly $2.8^\circ{\rm |
| 351 |
degree}$ resolution). |
| 352 |
|
| 353 |
\item \textit{advect\_cs} Two-dimensional passive advection test on |
| 354 |
cube sphere grid. |
| 355 |
|
| 356 |
\item \textit{advect\_xy} Two-dimensional (horizontal plane) passive |
| 357 |
advection test on Cartesian grid. |
| 358 |
|
| 359 |
\item \textit{advect\_yz} Two-dimensional (vertical plane) passive |
| 360 |
advection test on Cartesian grid. |
| 361 |
|
| 362 |
\item \textit{carbon} Simple passive tracer experiment. Includes |
| 363 |
derivative calculation. Described in detail in section |
| 364 |
\ref{sect:eg-carbon-ad}. |
| 365 |
|
| 366 |
\item \textit{flt\_example} Example of using float package. |
| 367 |
|
| 368 |
\item \textit{global\_ocean.90x40x15} Global circulation with GM, flux |
| 369 |
boundary conditions and poles. |
| 370 |
|
| 371 |
\item \textit{global\_ocean\_pressure} Global circulation in pressure |
| 372 |
coordinate (non-Boussinesq ocean model). Described in detail in |
| 373 |
section \ref{sect:eg-globalpressure}. |
| 374 |
|
| 375 |
\item \textit{solid-body.cs-32x32x1} Solid body rotation test for cube |
| 376 |
sphere grid. |
| 377 |
|
| 378 |
\end{enumerate} |
| 379 |
|
| 380 |
\subsection{Directory structure of model examples} |
| 381 |
|
| 382 |
Each example directory has the following subdirectories: |
| 383 |
|
| 384 |
\begin{itemize} |
| 385 |
\item \textit{code}: contains the code particular to the example. At a |
| 386 |
minimum, this directory includes the following files: |
| 387 |
|
| 388 |
\begin{itemize} |
| 389 |
\item \textit{code/CPP\_EEOPTIONS.h}: declares CPP keys relative to |
| 390 |
the ``execution environment'' part of the code. The default version |
| 391 |
is located in \textit{eesupp/inc}. |
| 392 |
|
| 393 |
\item \textit{code/CPP\_OPTIONS.h}: declares CPP keys relative to the |
| 394 |
``numerical model'' part of the code. The default version is located |
| 395 |
in \textit{model/inc}. |
| 396 |
|
| 397 |
\item \textit{code/SIZE.h}: declares size of underlying computational |
| 398 |
grid. The default version is located in \textit{model/inc}. |
| 399 |
\end{itemize} |
| 400 |
|
| 401 |
In addition, other include files and subroutines might be present in |
| 402 |
\textit{code} depending on the particular experiment. See Section 2 |
| 403 |
for more details. |
| 404 |
|
| 405 |
\item \textit{input}: contains the input data files required to run |
| 406 |
the example. At a minimum, the \textit{input} directory contains the |
| 407 |
following files: |
| 408 |
|
| 409 |
\begin{itemize} |
| 410 |
\item \textit{input/data}: this file, written as a namelist, specifies |
| 411 |
the main parameters for the experiment. |
| 412 |
|
| 413 |
\item \textit{input/data.pkg}: contains parameters relative to the |
| 414 |
packages used in the experiment. |
| 415 |
|
| 416 |
\item \textit{input/eedata}: this file contains ``execution |
| 417 |
environment'' data. At present, this consists of a specification of |
| 418 |
the number of threads to use in $X$ and $Y$ under multithreaded |
| 419 |
execution. |
| 420 |
\end{itemize} |
| 421 |
|
| 422 |
In addition, you will also find in this directory the forcing and topography |
| 423 |
files as well as the files describing the initial state of the experiment. |
| 424 |
This varies from experiment to experiment. See section 2 for more details. |
| 425 |
|
| 426 |
\item \textit{results}: this directory contains the output file \textit{% |
| 427 |
output.txt} produced by the simulation example. This file is useful for |
| 428 |
comparison with your own output when you run the experiment. |
| 429 |
\end{itemize} |
| 430 |
|
| 431 |
Once you have chosen the example you want to run, you are ready to compile |
| 432 |
the code. |
| 433 |
|
| 434 |
\section{Building the code} |
| 435 |
\label{sect:buildingCode} |
| 436 |
|
| 437 |
To compile the code, we use the {\em make} program. This uses a file |
| 438 |
({\em Makefile}) that allows us to pre-process source files, specify |
| 439 |
compiler and optimization options and also figures out any file |
| 440 |
dependencies. We supply a script ({\em genmake}), described in section |
| 441 |
\ref{sect:genmake}, that automatically creates the {\em Makefile} for |
| 442 |
you. You then need to build the dependencies and compile the code. |
| 443 |
|
| 444 |
As an example, let's assume that you want to build and run experiment |
| 445 |
\textit{verification/exp2}. The are multiple ways and places to actually |
| 446 |
do this but here let's build the code in |
| 447 |
\textit{verification/exp2/input}: |
| 448 |
\begin{verbatim} |
| 449 |
% cd verification/exp2/input |
| 450 |
\end{verbatim} |
| 451 |
First, build the {\em Makefile}: |
| 452 |
\begin{verbatim} |
| 453 |
% ../../../tools/genmake -mods=../code |
| 454 |
\end{verbatim} |
| 455 |
The command line option tells {\em genmake} to override model source |
| 456 |
code with any files in the directory {\em ./code/}. |
| 457 |
|
| 458 |
If there is no \textit{.genmakerc} in the \textit{input} directory, you have |
| 459 |
to use the following options when invoking \textit{genmake}: |
| 460 |
\begin{verbatim} |
| 461 |
% ../../../tools/genmake -mods=../code |
| 462 |
\end{verbatim} |
| 463 |
|
| 464 |
Next, create the dependencies: |
| 465 |
\begin{verbatim} |
| 466 |
% make depend |
| 467 |
\end{verbatim} |
| 468 |
This modifies {\em Makefile} by attaching a [long] list of files on |
| 469 |
which other files depend. The purpose of this is to reduce |
| 470 |
re-compilation if and when you start to modify the code. {\tt make |
| 471 |
depend} also created links from the model source to this directory. |
| 472 |
|
| 473 |
Now compile the code: |
| 474 |
\begin{verbatim} |
| 475 |
% make |
| 476 |
\end{verbatim} |
| 477 |
The {\tt make} command creates an executable called \textit{mitgcmuv}. |
| 478 |
|
| 479 |
Now you are ready to run the model. General instructions for doing so are |
| 480 |
given in section \ref{sect:runModel}. Here, we can run the model with: |
| 481 |
\begin{verbatim} |
| 482 |
./mitgcmuv > output.txt |
| 483 |
\end{verbatim} |
| 484 |
where we are re-directing the stream of text output to the file {\em |
| 485 |
output.txt}. |
| 486 |
|
| 487 |
|
| 488 |
\subsection{Building/compiling the code elsewhere} |
| 489 |
|
| 490 |
In the example above (section \ref{sect:buildingCode}) we built the |
| 491 |
executable in the {\em input} directory of the experiment for |
| 492 |
convenience. You can also configure and compile the code in other |
| 493 |
locations, for example on a scratch disk with out having to copy the |
| 494 |
entire source tree. The only requirement to do so is you have {\tt |
| 495 |
genmake} in your path or you know the absolute path to {\tt genmake}. |
| 496 |
|
| 497 |
The following sections outline some possible methods of organizing you |
| 498 |
source and data. |
| 499 |
|
| 500 |
\subsubsection{Building from the {\em ../code directory}} |
| 501 |
|
| 502 |
This is just as simple as building in the {\em input/} directory: |
| 503 |
\begin{verbatim} |
| 504 |
% cd verification/exp2/code |
| 505 |
% ../../../tools/genmake |
| 506 |
% make depend |
| 507 |
% make |
| 508 |
\end{verbatim} |
| 509 |
However, to run the model the executable ({\em mitgcmuv}) and input |
| 510 |
files must be in the same place. If you only have one calculation to make: |
| 511 |
\begin{verbatim} |
| 512 |
% cd ../input |
| 513 |
% cp ../code/mitgcmuv ./ |
| 514 |
% ./mitgcmuv > output.txt |
| 515 |
\end{verbatim} |
| 516 |
or if you will be making multiple runs with the same executable: |
| 517 |
\begin{verbatim} |
| 518 |
% cd ../ |
| 519 |
% cp -r input run1 |
| 520 |
% cp code/mitgcmuv run1 |
| 521 |
% cd run1 |
| 522 |
% ./mitgcmuv > output.txt |
| 523 |
\end{verbatim} |
| 524 |
|
| 525 |
\subsubsection{Building from a new directory} |
| 526 |
|
| 527 |
Since the {\em input} directory contains input files it is often more |
| 528 |
useful to keep {\em input} pristine and build in a new directory |
| 529 |
within {\em verification/exp2/}: |
| 530 |
\begin{verbatim} |
| 531 |
% cd verification/exp2 |
| 532 |
% mkdir build |
| 533 |
% cd build |
| 534 |
% ../../../tools/genmake -mods=../code |
| 535 |
% make depend |
| 536 |
% make |
| 537 |
\end{verbatim} |
| 538 |
This builds the code exactly as before but this time you need to copy |
| 539 |
either the executable or the input files or both in order to run the |
| 540 |
model. For example, |
| 541 |
\begin{verbatim} |
| 542 |
% cp ../input/* ./ |
| 543 |
% ./mitgcmuv > output.txt |
| 544 |
\end{verbatim} |
| 545 |
or if you tend to make multiple runs with the same executable then |
| 546 |
running in a new directory each time might be more appropriate: |
| 547 |
\begin{verbatim} |
| 548 |
% cd ../ |
| 549 |
% mkdir run1 |
| 550 |
% cp build/mitgcmuv run1/ |
| 551 |
% cp input/* run1/ |
| 552 |
% cd run1 |
| 553 |
% ./mitgcmuv > output.txt |
| 554 |
\end{verbatim} |
| 555 |
|
| 556 |
\subsubsection{Building from on a scratch disk} |
| 557 |
|
| 558 |
Model object files and output data can use up large amounts of disk |
| 559 |
space so it is often the case that you will be operating on a large |
| 560 |
scratch disk. Assuming the model source is in {\em ~/MITgcm} then the |
| 561 |
following commands will build the model in {\em /scratch/exp2-run1}: |
| 562 |
\begin{verbatim} |
| 563 |
% cd /scratch/exp2-run1 |
| 564 |
% ~/MITgcm/tools/genmake -rootdir=~/MITgcm -mods=~/MITgcm/verification/exp2/code |
| 565 |
% make depend |
| 566 |
% make |
| 567 |
\end{verbatim} |
| 568 |
To run the model here, you'll need the input files: |
| 569 |
\begin{verbatim} |
| 570 |
% cp ~/MITgcm/verification/exp2/input/* ./ |
| 571 |
% ./mitgcmuv > output.txt |
| 572 |
\end{verbatim} |
| 573 |
|
| 574 |
As before, you could build in one directory and make multiple runs of |
| 575 |
the one experiment: |
| 576 |
\begin{verbatim} |
| 577 |
% cd /scratch/exp2 |
| 578 |
% mkdir build |
| 579 |
% cd build |
| 580 |
% ~/MITgcm/tools/genmake -rootdir=~/MITgcm -mods=~/MITgcm/verification/exp2/code |
| 581 |
% make depend |
| 582 |
% make |
| 583 |
% cd ../ |
| 584 |
% cp -r ~/MITgcm/verification/exp2/input run2 |
| 585 |
% cd run2 |
| 586 |
% ./mitgcmuv > output.txt |
| 587 |
\end{verbatim} |
| 588 |
|
| 589 |
|
| 590 |
|
| 591 |
\subsection{\textit{genmake}} |
| 592 |
\label{sect:genmake} |
| 593 |
|
| 594 |
To compile the code, use the script \textit{genmake} located in the \textit{% |
| 595 |
tools} directory. \textit{genmake} is a script that generates the makefile. |
| 596 |
It has been written so that the code can be compiled on a wide diversity of |
| 597 |
machines and systems. However, if it doesn't work the first time on your |
| 598 |
platform, you might need to edit certain lines of \textit{genmake} in the |
| 599 |
section containing the setups for the different machines. The file is |
| 600 |
structured like this: |
| 601 |
\begin{verbatim} |
| 602 |
. |
| 603 |
. |
| 604 |
. |
| 605 |
general instructions (machine independent) |
| 606 |
. |
| 607 |
. |
| 608 |
. |
| 609 |
- setup machine 1 |
| 610 |
- setup machine 2 |
| 611 |
- setup machine 3 |
| 612 |
- setup machine 4 |
| 613 |
etc |
| 614 |
. |
| 615 |
. |
| 616 |
. |
| 617 |
\end{verbatim} |
| 618 |
|
| 619 |
For example, the setup corresponding to a DEC alpha machine is reproduced |
| 620 |
here: |
| 621 |
\begin{verbatim} |
| 622 |
case OSF1+mpi: |
| 623 |
echo "Configuring for DEC Alpha" |
| 624 |
set CPP = ( '/usr/bin/cpp -P' ) |
| 625 |
set DEFINES = ( ${DEFINES} '-DTARGET_DEC -DWORDLENGTH=1' ) |
| 626 |
set KPP = ( 'kapf' ) |
| 627 |
set KPPFILES = ( 'main.F' ) |
| 628 |
set KFLAGS1 = ( '-scan=132 -noconc -cmp=' ) |
| 629 |
set FC = ( 'f77' ) |
| 630 |
set FFLAGS = ( '-convert big_endian -r8 -extend_source -automatic -call_shared -notransform_loops -align dcommons' ) |
| 631 |
set FOPTIM = ( '-O5 -fast -tune host -inline all' ) |
| 632 |
set NOOPTFLAGS = ( '-O0' ) |
| 633 |
set LIBS = ( '-lfmpi -lmpi -lkmp_osfp10 -pthread' ) |
| 634 |
set NOOPTFILES = ( 'barrier.F different_multiple.F external_fields_load.F') |
| 635 |
set RMFILES = ( '*.p.out' ) |
| 636 |
breaksw |
| 637 |
\end{verbatim} |
| 638 |
|
| 639 |
Typically, these are the lines that you might need to edit to make \textit{% |
| 640 |
genmake} work on your platform if it doesn't work the first time. \textit{% |
| 641 |
genmake} understands several options that are described here: |
| 642 |
|
| 643 |
\begin{itemize} |
| 644 |
\item -rootdir=dir |
| 645 |
|
| 646 |
indicates where the model root directory is relative to the directory where |
| 647 |
you are compiling. This option is not needed if you compile in the \textit{% |
| 648 |
bin} directory (which is the default compilation directory) or within the |
| 649 |
\textit{verification} tree. |
| 650 |
|
| 651 |
\item -mods=dir1,dir2,... |
| 652 |
|
| 653 |
indicates the relative or absolute paths directories where the sources |
| 654 |
should take precedence over the default versions (located in \textit{model}, |
| 655 |
\textit{eesupp},...). Typically, this option is used when running the |
| 656 |
examples, see below. |
| 657 |
|
| 658 |
\item -enable=pkg1,pkg2,... |
| 659 |
|
| 660 |
enables packages source code \textit{pkg1}, \textit{pkg2},... when creating |
| 661 |
the makefile. |
| 662 |
|
| 663 |
\item -disable=pkg1,pkg2,... |
| 664 |
|
| 665 |
disables packages source code \textit{pkg1}, \textit{pkg2},... when creating |
| 666 |
the makefile. |
| 667 |
|
| 668 |
\item -platform=machine |
| 669 |
|
| 670 |
specifies the platform for which you want the makefile. In general, you |
| 671 |
won't need this option. \textit{genmake} will select the right machine for |
| 672 |
you (the one you're working on!). However, this option is useful if you have |
| 673 |
a choice of several compilers on one machine and you want to use the one |
| 674 |
that is not the default (ex: \texttt{pgf77} instead of \texttt{f77} under |
| 675 |
Linux). |
| 676 |
|
| 677 |
\item -mpi |
| 678 |
|
| 679 |
this is used when you want to run the model in parallel processing mode |
| 680 |
under mpi (see section on parallel computation for more details). |
| 681 |
|
| 682 |
\item -jam |
| 683 |
|
| 684 |
this is used when you want to run the model in parallel processing mode |
| 685 |
under jam (see section on parallel computation for more details). |
| 686 |
\end{itemize} |
| 687 |
|
| 688 |
For some of the examples, there is a file called \textit{.genmakerc} in the |
| 689 |
\textit{input} directory that has the relevant \textit{genmake} options for |
| 690 |
that particular example. In this way you don't need to type the options when |
| 691 |
invoking \textit{genmake}. |
| 692 |
|
| 693 |
|
| 694 |
\section{Running the model} |
| 695 |
\label{sect:runModel} |
| 696 |
|
| 697 |
If compilation finished succesfuully (section \ref{sect:buildModel}) |
| 698 |
then an executable called {\em mitgcmuv} will now exist in the local |
| 699 |
directory. |
| 700 |
|
| 701 |
To run the model as a single process (ie. not in parallel) simply |
| 702 |
type: |
| 703 |
\begin{verbatim} |
| 704 |
% ./mitgcmuv |
| 705 |
\end{verbatim} |
| 706 |
The ``./'' is a safe-guard to make sure you use the local executable |
| 707 |
in case you have others that exist in your path (surely odd if you |
| 708 |
do!). The above command will spew out many lines of text output to |
| 709 |
your screen. This output contains details such as parameter values as |
| 710 |
well as diagnostics such as mean Kinetic energy, largest CFL number, |
| 711 |
etc. It is worth keeping this text output with the binary output so we |
| 712 |
normally re-direct the {\em stdout} stream as follows: |
| 713 |
\begin{verbatim} |
| 714 |
% ./mitgcmuv > output.txt |
| 715 |
\end{verbatim} |
| 716 |
|
| 717 |
For the example experiments in {\em vericication}, an example of the |
| 718 |
output is kept in {\em results/output.txt} for comparison. You can compare |
| 719 |
your {\em output.txt} with this one to check that the set-up works. |
| 720 |
|
| 721 |
|
| 722 |
|
| 723 |
\subsection{Output files} |
| 724 |
|
| 725 |
The model produces various output files. At a minimum, the instantaneous |
| 726 |
``state'' of the model is written out, which is made of the following files: |
| 727 |
|
| 728 |
\begin{itemize} |
| 729 |
\item \textit{U.00000nIter} - zonal component of velocity field (m/s and $> |
| 730 |
0 $ eastward). |
| 731 |
|
| 732 |
\item \textit{V.00000nIter} - meridional component of velocity field (m/s |
| 733 |
and $> 0$ northward). |
| 734 |
|
| 735 |
\item \textit{W.00000nIter} - vertical component of velocity field (ocean: |
| 736 |
m/s and $> 0$ upward, atmosphere: Pa/s and $> 0$ towards increasing pressure |
| 737 |
i.e. downward). |
| 738 |
|
| 739 |
\item \textit{T.00000nIter} - potential temperature (ocean: $^{0}$C, |
| 740 |
atmosphere: $^{0}$K). |
| 741 |
|
| 742 |
\item \textit{S.00000nIter} - ocean: salinity (psu), atmosphere: water vapor |
| 743 |
(g/kg). |
| 744 |
|
| 745 |
\item \textit{Eta.00000nIter} - ocean: surface elevation (m), atmosphere: |
| 746 |
surface pressure anomaly (Pa). |
| 747 |
\end{itemize} |
| 748 |
|
| 749 |
The chain \textit{00000nIter} consists of ten figures that specify the |
| 750 |
iteration number at which the output is written out. For example, \textit{% |
| 751 |
U.0000000300} is the zonal velocity at iteration 300. |
| 752 |
|
| 753 |
In addition, a ``pickup'' or ``checkpoint'' file called: |
| 754 |
|
| 755 |
\begin{itemize} |
| 756 |
\item \textit{pickup.00000nIter} |
| 757 |
\end{itemize} |
| 758 |
|
| 759 |
is written out. This file represents the state of the model in a condensed |
| 760 |
form and is used for restarting the integration. If the C-D scheme is used, |
| 761 |
there is an additional ``pickup'' file: |
| 762 |
|
| 763 |
\begin{itemize} |
| 764 |
\item \textit{pickup\_cd.00000nIter} |
| 765 |
\end{itemize} |
| 766 |
|
| 767 |
containing the D-grid velocity data and that has to be written out as well |
| 768 |
in order to restart the integration. Rolling checkpoint files are the same |
| 769 |
as the pickup files but are named differently. Their name contain the chain |
| 770 |
\textit{ckptA} or \textit{ckptB} instead of \textit{00000nIter}. They can be |
| 771 |
used to restart the model but are overwritten every other time they are |
| 772 |
output to save disk space during long integrations. |
| 773 |
|
| 774 |
\subsection{Looking at the output} |
| 775 |
|
| 776 |
All the model data are written according to a ``meta/data'' file format. |
| 777 |
Each variable is associated with two files with suffix names \textit{.data} |
| 778 |
and \textit{.meta}. The \textit{.data} file contains the data written in |
| 779 |
binary form (big\_endian by default). The \textit{.meta} file is a |
| 780 |
``header'' file that contains information about the size and the structure |
| 781 |
of the \textit{.data} file. This way of organizing the output is |
| 782 |
particularly useful when running multi-processors calculations. The base |
| 783 |
version of the model includes a few matlab utilities to read output files |
| 784 |
written in this format. The matlab scripts are located in the directory |
| 785 |
\textit{utils/matlab} under the root tree. The script \textit{rdmds.m} reads |
| 786 |
the data. Look at the comments inside the script to see how to use it. |
| 787 |
|
| 788 |
Some examples of reading and visualizing some output in {\em Matlab}: |
| 789 |
\begin{verbatim} |
| 790 |
% matlab |
| 791 |
>> H=rdmds('Depth'); |
| 792 |
>> contourf(H');colorbar; |
| 793 |
>> title('Depth of fluid as used by model'); |
| 794 |
|
| 795 |
>> eta=rdmds('Eta',10); |
| 796 |
>> imagesc(eta');axis ij;colorbar; |
| 797 |
>> title('Surface height at iter=10'); |
| 798 |
|
| 799 |
>> eta=rdmds('Eta',[0:10:100]); |
| 800 |
>> for n=1:11; imagesc(eta(:,:,n)');axis ij;colorbar;pause(.5);end |
| 801 |
\end{verbatim} |
| 802 |
|
| 803 |
\section{Doing it yourself: customizing the code} |
| 804 |
|
| 805 |
When you are ready to run the model in the configuration you want, the |
| 806 |
easiest thing is to use and adapt the setup of the case studies experiment |
| 807 |
(described previously) that is the closest to your configuration. Then, the |
| 808 |
amount of setup will be minimized. In this section, we focus on the setup |
| 809 |
relative to the ''numerical model'' part of the code (the setup relative to |
| 810 |
the ''execution environment'' part is covered in the parallel implementation |
| 811 |
section) and on the variables and parameters that you are likely to change. |
| 812 |
|
| 813 |
\subsection{Configuration and setup} |
| 814 |
|
| 815 |
The CPP keys relative to the ''numerical model'' part of the code are all |
| 816 |
defined and set in the file \textit{CPP\_OPTIONS.h }in the directory \textit{% |
| 817 |
model/inc }or in one of the \textit{code }directories of the case study |
| 818 |
experiments under \textit{verification.} The model parameters are defined |
| 819 |
and declared in the file \textit{model/inc/PARAMS.h }and their default |
| 820 |
values are set in the routine \textit{model/src/set\_defaults.F. }The |
| 821 |
default values can be modified in the namelist file \textit{data }which |
| 822 |
needs to be located in the directory where you will run the model. The |
| 823 |
parameters are initialized in the routine \textit{model/src/ini\_parms.F}. |
| 824 |
Look at this routine to see in what part of the namelist the parameters are |
| 825 |
located. |
| 826 |
|
| 827 |
In what follows the parameters are grouped into categories related to the |
| 828 |
computational domain, the equations solved in the model, and the simulation |
| 829 |
controls. |
| 830 |
|
| 831 |
\subsection{Computational domain, geometry and time-discretization} |
| 832 |
|
| 833 |
\begin{itemize} |
| 834 |
\item dimensions |
| 835 |
\end{itemize} |
| 836 |
|
| 837 |
The number of points in the x, y,\textit{\ }and r\textit{\ }directions are |
| 838 |
represented by the variables \textbf{sNx}\textit{, }\textbf{sNy}\textit{, }% |
| 839 |
and \textbf{Nr}\textit{\ }respectively which are declared and set in the |
| 840 |
file \textit{model/inc/SIZE.h. }(Again, this assumes a mono-processor |
| 841 |
calculation. For multiprocessor calculations see section on parallel |
| 842 |
implementation.) |
| 843 |
|
| 844 |
\begin{itemize} |
| 845 |
\item grid |
| 846 |
\end{itemize} |
| 847 |
|
| 848 |
Three different grids are available: cartesian, spherical polar, and |
| 849 |
curvilinear (including the cubed sphere). The grid is set through the |
| 850 |
logical variables \textbf{usingCartesianGrid}\textit{, }\textbf{% |
| 851 |
usingSphericalPolarGrid}\textit{, }and \textit{\ }\textbf{% |
| 852 |
usingCurvilinearGrid}\textit{. }In the case of spherical and curvilinear |
| 853 |
grids, the southern boundary is defined through the variable \textbf{phiMin}% |
| 854 |
\textit{\ }which corresponds to the latitude of the southern most cell face |
| 855 |
(in degrees). The resolution along the x and y directions is controlled by |
| 856 |
the 1D arrays \textbf{delx}\textit{\ }and \textbf{dely}\textit{\ }(in meters |
| 857 |
in the case of a cartesian grid, in degrees otherwise). The vertical grid |
| 858 |
spacing is set through the 1D array \textbf{delz }for the ocean (in meters) |
| 859 |
or \textbf{delp}\textit{\ }for the atmosphere (in Pa). The variable \textbf{% |
| 860 |
Ro\_SeaLevel} represents the standard position of Sea-Level in ''R'' |
| 861 |
coordinate. This is typically set to 0m for the ocean (default value) and 10$% |
| 862 |
^{5}$Pa for the atmosphere. For the atmosphere, also set the logical |
| 863 |
variable \textbf{groundAtK1} to '.\texttt{TRUE}.'. which put the first level |
| 864 |
(k=1) at the lower boundary (ground). |
| 865 |
|
| 866 |
For the cartesian grid case, the Coriolis parameter $f$ is set through the |
| 867 |
variables \textbf{f0}\textit{\ }and \textbf{beta}\textit{\ }which correspond |
| 868 |
to the reference Coriolis parameter (in s$^{-1}$) and $\frac{\partial f}{% |
| 869 |
\partial y}$(in m$^{-1}$s$^{-1}$) respectively. If \textbf{beta }\textit{\ }% |
| 870 |
is set to a nonzero value, \textbf{f0}\textit{\ }is the value of $f$ at the |
| 871 |
southern edge of the domain. |
| 872 |
|
| 873 |
\begin{itemize} |
| 874 |
\item topography - full and partial cells |
| 875 |
\end{itemize} |
| 876 |
|
| 877 |
The domain bathymetry is read from a file that contains a 2D (x,y) map of |
| 878 |
depths (in m) for the ocean or pressures (in Pa) for the atmosphere. The |
| 879 |
file name is represented by the variable \textbf{bathyFile}\textit{. }The |
| 880 |
file is assumed to contain binary numbers giving the depth (pressure) of the |
| 881 |
model at each grid cell, ordered with the x coordinate varying fastest. The |
| 882 |
points are ordered from low coordinate to high coordinate for both axes. The |
| 883 |
model code applies without modification to enclosed, periodic, and double |
| 884 |
periodic domains. Periodicity is assumed by default and is suppressed by |
| 885 |
setting the depths to 0m for the cells at the limits of the computational |
| 886 |
domain (note: not sure this is the case for the atmosphere). The precision |
| 887 |
with which to read the binary data is controlled by the integer variable |
| 888 |
\textbf{readBinaryPrec }which can take the value \texttt{32} (single |
| 889 |
precision) or \texttt{64} (double precision). See the matlab program \textit{% |
| 890 |
gendata.m }in the \textit{input }directories under \textit{verification }to |
| 891 |
see how the bathymetry files are generated for the case study experiments. |
| 892 |
|
| 893 |
To use the partial cell capability, the variable \textbf{hFacMin}\textit{\ }% |
| 894 |
needs to be set to a value between 0 and 1 (it is set to 1 by default) |
| 895 |
corresponding to the minimum fractional size of the cell. For example if the |
| 896 |
bottom cell is 500m thick and \textbf{hFacMin}\textit{\ }is set to 0.1, the |
| 897 |
actual thickness of the cell (i.e. used in the code) can cover a range of |
| 898 |
discrete values 50m apart from 50m to 500m depending on the value of the |
| 899 |
bottom depth (in \textbf{bathyFile}) at this point. |
| 900 |
|
| 901 |
Note that the bottom depths (or pressures) need not coincide with the models |
| 902 |
levels as deduced from \textbf{delz}\textit{\ }or\textit{\ }\textbf{delp}% |
| 903 |
\textit{. }The model will interpolate the numbers in \textbf{bathyFile}% |
| 904 |
\textit{\ }so that they match the levels obtained from \textbf{delz}\textit{% |
| 905 |
\ }or\textit{\ }\textbf{delp}\textit{\ }and \textbf{hFacMin}\textit{. } |
| 906 |
|
| 907 |
(Note: the atmospheric case is a bit more complicated than what is written |
| 908 |
here I think. To come soon...) |
| 909 |
|
| 910 |
\begin{itemize} |
| 911 |
\item time-discretization |
| 912 |
\end{itemize} |
| 913 |
|
| 914 |
The time steps are set through the real variables \textbf{deltaTMom} |
| 915 |
and \textbf{deltaTtracer} (in s) which represent the time step for the |
| 916 |
momentum and tracer equations, respectively. For synchronous |
| 917 |
integrations, simply set the two variables to the same value (or you |
| 918 |
can prescribe one time step only through the variable |
| 919 |
\textbf{deltaT}). The Adams-Bashforth stabilizing parameter is set |
| 920 |
through the variable \textbf{abEps} (dimensionless). The stagger |
| 921 |
baroclinic time stepping can be activated by setting the logical |
| 922 |
variable \textbf{staggerTimeStep} to '.\texttt{TRUE}.'. |
| 923 |
|
| 924 |
\subsection{Equation of state} |
| 925 |
|
| 926 |
First, because the model equations are written in terms of |
| 927 |
perturbations, a reference thermodynamic state needs to be specified. |
| 928 |
This is done through the 1D arrays \textbf{tRef} and \textbf{sRef}. |
| 929 |
\textbf{tRef} specifies the reference potential temperature profile |
| 930 |
(in $^{o}$C for the ocean and $^{o}$K for the atmosphere) starting |
| 931 |
from the level k=1. Similarly, \textbf{sRef} specifies the reference |
| 932 |
salinity profile (in ppt) for the ocean or the reference specific |
| 933 |
humidity profile (in g/kg) for the atmosphere. |
| 934 |
|
| 935 |
The form of the equation of state is controlled by the character |
| 936 |
variables \textbf{buoyancyRelation} and \textbf{eosType}. |
| 937 |
\textbf{buoyancyRelation} is set to '\texttt{OCEANIC}' by default and |
| 938 |
needs to be set to '\texttt{ATMOSPHERIC}' for atmosphere simulations. |
| 939 |
In this case, \textbf{eosType} must be set to '\texttt{IDEALGAS}'. |
| 940 |
For the ocean, two forms of the equation of state are available: |
| 941 |
linear (set \textbf{eosType} to '\texttt{LINEAR}') and a polynomial |
| 942 |
approximation to the full nonlinear equation ( set |
| 943 |
\textbf{eosType}\textit{\ }to '\texttt{POLYNOMIAL}'). In the linear |
| 944 |
case, you need to specify the thermal and haline expansion |
| 945 |
coefficients represented by the variables \textbf{tAlpha}\textit{\ |
| 946 |
}(in K$^{-1}$) and \textbf{sBeta} (in ppt$^{-1}$). For the nonlinear |
| 947 |
case, you need to generate a file of polynomial coefficients called |
| 948 |
\textit{POLY3.COEFFS}. To do this, use the program |
| 949 |
\textit{utils/knudsen2/knudsen2.f} under the model tree (a Makefile is |
| 950 |
available in the same directory and you will need to edit the number |
| 951 |
and the values of the vertical levels in \textit{knudsen2.f} so that |
| 952 |
they match those of your configuration). |
| 953 |
|
| 954 |
There there are also higher polynomials for the equation of state: |
| 955 |
\begin{description} |
| 956 |
\item['\texttt{UNESCO}':] The UNESCO equation of state formula of |
| 957 |
Fofonoff and Millard \cite{fofonoff83}. This equation of state |
| 958 |
assumes in-situ temperature, which is not a model variable; \emph{its use |
| 959 |
is therefore discouraged, and it is only listed for completeness}. |
| 960 |
\item['\texttt{JMD95Z}':] A modified UNESCO formula by Jackett and |
| 961 |
McDougall \cite{jackett95}, which uses the model variable potential |
| 962 |
temperature as input. The '\texttt{Z}' indicates that this equation |
| 963 |
of state uses a horizontally and temporally constant pressure |
| 964 |
$p_{0}=-g\rho_{0}z$. |
| 965 |
\item['\texttt{JMD95P}':] A modified UNESCO formula by Jackett and |
| 966 |
McDougall \cite{jackett95}, which uses the model variable potential |
| 967 |
temperature as input. The '\texttt{P}' indicates that this equation |
| 968 |
of state uses the actual hydrostatic pressure of the last time |
| 969 |
step. Lagging the pressure in this way requires an additional pickup |
| 970 |
file for restarts. |
| 971 |
\item['\texttt{MDJWF}':] The new, more accurate and less expensive |
| 972 |
equation of state by McDougall et~al. \cite{mcdougall03}. It also |
| 973 |
requires lagging the pressure and therefore an additional pickup |
| 974 |
file for restarts. |
| 975 |
\end{description} |
| 976 |
For none of these options an reference profile of temperature or |
| 977 |
salinity is required. |
| 978 |
|
| 979 |
\subsection{Momentum equations} |
| 980 |
|
| 981 |
In this section, we only focus for now on the parameters that you are likely |
| 982 |
to change, i.e. the ones relative to forcing and dissipation for example. |
| 983 |
The details relevant to the vector-invariant form of the equations and the |
| 984 |
various advection schemes are not covered for the moment. We assume that you |
| 985 |
use the standard form of the momentum equations (i.e. the flux-form) with |
| 986 |
the default advection scheme. Also, there are a few logical variables that |
| 987 |
allow you to turn on/off various terms in the momentum equation. These |
| 988 |
variables are called \textbf{momViscosity, momAdvection, momForcing, |
| 989 |
useCoriolis, momPressureForcing, momStepping}\textit{, }and \textit{\ }% |
| 990 |
\textbf{metricTerms }and are assumed to be set to '.\texttt{TRUE}.' here. |
| 991 |
Look at the file \textit{model/inc/PARAMS.h }for a precise definition of |
| 992 |
these variables. |
| 993 |
|
| 994 |
\begin{itemize} |
| 995 |
\item initialization |
| 996 |
\end{itemize} |
| 997 |
|
| 998 |
The velocity components are initialized to 0 unless the simulation is |
| 999 |
starting from a pickup file (see section on simulation control parameters). |
| 1000 |
|
| 1001 |
\begin{itemize} |
| 1002 |
\item forcing |
| 1003 |
\end{itemize} |
| 1004 |
|
| 1005 |
This section only applies to the ocean. You need to generate wind-stress |
| 1006 |
data into two files \textbf{zonalWindFile}\textit{\ }and \textbf{% |
| 1007 |
meridWindFile }corresponding to the zonal and meridional components of the |
| 1008 |
wind stress, respectively (if you want the stress to be along the direction |
| 1009 |
of only one of the model horizontal axes, you only need to generate one |
| 1010 |
file). The format of the files is similar to the bathymetry file. The zonal |
| 1011 |
(meridional) stress data are assumed to be in Pa and located at U-points |
| 1012 |
(V-points). As for the bathymetry, the precision with which to read the |
| 1013 |
binary data is controlled by the variable \textbf{readBinaryPrec}.\textbf{\ } |
| 1014 |
See the matlab program \textit{gendata.m }in the \textit{input }directories |
| 1015 |
under \textit{verification }to see how simple analytical wind forcing data |
| 1016 |
are generated for the case study experiments. |
| 1017 |
|
| 1018 |
There is also the possibility of prescribing time-dependent periodic |
| 1019 |
forcing. To do this, concatenate the successive time records into a single |
| 1020 |
file (for each stress component) ordered in a (x, y, t) fashion and set the |
| 1021 |
following variables: \textbf{periodicExternalForcing }to '.\texttt{TRUE}.', |
| 1022 |
\textbf{externForcingPeriod }to the period (in s) of which the forcing |
| 1023 |
varies (typically 1 month), and \textbf{externForcingCycle }to the repeat |
| 1024 |
time (in s) of the forcing (typically 1 year -- note: \textbf{% |
| 1025 |
externForcingCycle }must be a multiple of \textbf{externForcingPeriod}). |
| 1026 |
With these variables set up, the model will interpolate the forcing linearly |
| 1027 |
at each iteration. |
| 1028 |
|
| 1029 |
\begin{itemize} |
| 1030 |
\item dissipation |
| 1031 |
\end{itemize} |
| 1032 |
|
| 1033 |
The lateral eddy viscosity coefficient is specified through the variable |
| 1034 |
\textbf{viscAh}\textit{\ }(in m$^{2}$s$^{-1}$). The vertical eddy viscosity |
| 1035 |
coefficient is specified through the variable \textbf{viscAz }(in m$^{2}$s$% |
| 1036 |
^{-1}$) for the ocean and \textbf{viscAp}\textit{\ }(in Pa$^{2}$s$^{-1}$) |
| 1037 |
for the atmosphere. The vertical diffusive fluxes can be computed implicitly |
| 1038 |
by setting the logical variable \textbf{implicitViscosity }to '.\texttt{TRUE}% |
| 1039 |
.'. In addition, biharmonic mixing can be added as well through the variable |
| 1040 |
\textbf{viscA4}\textit{\ }(in m$^{4}$s$^{-1}$). On a spherical polar grid, |
| 1041 |
you might also need to set the variable \textbf{cosPower} which is set to 0 |
| 1042 |
by default and which represents the power of cosine of latitude to multiply |
| 1043 |
viscosity. Slip or no-slip conditions at lateral and bottom boundaries are |
| 1044 |
specified through the logical variables \textbf{no\_slip\_sides}\textit{\ }% |
| 1045 |
and \textbf{no\_slip\_bottom}. If set to '\texttt{.FALSE.}', free-slip |
| 1046 |
boundary conditions are applied. If no-slip boundary conditions are applied |
| 1047 |
at the bottom, a bottom drag can be applied as well. Two forms are |
| 1048 |
available: linear (set the variable \textbf{bottomDragLinear}\textit{\ }in s$% |
| 1049 |
^{-1}$) and quadratic (set the variable \textbf{bottomDragQuadratic}\textit{% |
| 1050 |
\ }in m$^{-1}$). |
| 1051 |
|
| 1052 |
The Fourier and Shapiro filters are described elsewhere. |
| 1053 |
|
| 1054 |
\begin{itemize} |
| 1055 |
\item C-D scheme |
| 1056 |
\end{itemize} |
| 1057 |
|
| 1058 |
If you run at a sufficiently coarse resolution, you will need the C-D scheme |
| 1059 |
for the computation of the Coriolis terms. The variable\textbf{\ tauCD}, |
| 1060 |
which represents the C-D scheme coupling timescale (in s) needs to be set. |
| 1061 |
|
| 1062 |
\begin{itemize} |
| 1063 |
\item calculation of pressure/geopotential |
| 1064 |
\end{itemize} |
| 1065 |
|
| 1066 |
First, to run a non-hydrostatic ocean simulation, set the logical variable |
| 1067 |
\textbf{nonHydrostatic} to '.\texttt{TRUE}.'. The pressure field is then |
| 1068 |
inverted through a 3D elliptic equation. (Note: this capability is not |
| 1069 |
available for the atmosphere yet.) By default, a hydrostatic simulation is |
| 1070 |
assumed and a 2D elliptic equation is used to invert the pressure field. The |
| 1071 |
parameters controlling the behaviour of the elliptic solvers are the |
| 1072 |
variables \textbf{cg2dMaxIters}\textit{\ }and \textbf{cg2dTargetResidual }% |
| 1073 |
for the 2D case and \textbf{cg3dMaxIters}\textit{\ }and \textbf{% |
| 1074 |
cg3dTargetResidual }for the 3D case. You probably won't need to alter the |
| 1075 |
default values (are we sure of this?). |
| 1076 |
|
| 1077 |
For the calculation of the surface pressure (for the ocean) or surface |
| 1078 |
geopotential (for the atmosphere) you need to set the logical variables |
| 1079 |
\textbf{rigidLid} and \textbf{implicitFreeSurface}\textit{\ }(set one to '.% |
| 1080 |
\texttt{TRUE}.' and the other to '.\texttt{FALSE}.' depending on how you |
| 1081 |
want to deal with the ocean upper or atmosphere lower boundary). |
| 1082 |
|
| 1083 |
\subsection{Tracer equations} |
| 1084 |
|
| 1085 |
This section covers the tracer equations i.e. the potential temperature |
| 1086 |
equation and the salinity (for the ocean) or specific humidity (for the |
| 1087 |
atmosphere) equation. As for the momentum equations, we only describe for |
| 1088 |
now the parameters that you are likely to change. The logical variables |
| 1089 |
\textbf{tempDiffusion}\textit{, }\textbf{tempAdvection}\textit{, }\textbf{% |
| 1090 |
tempForcing}\textit{,} and \textbf{tempStepping} allow you to turn on/off |
| 1091 |
terms in the temperature equation (same thing for salinity or specific |
| 1092 |
humidity with variables \textbf{saltDiffusion}\textit{, }\textbf{% |
| 1093 |
saltAdvection}\textit{\ }etc). These variables are all assumed here to be |
| 1094 |
set to '.\texttt{TRUE}.'. Look at file \textit{model/inc/PARAMS.h }for a |
| 1095 |
precise definition. |
| 1096 |
|
| 1097 |
\begin{itemize} |
| 1098 |
\item initialization |
| 1099 |
\end{itemize} |
| 1100 |
|
| 1101 |
The initial tracer data can be contained in the binary files \textbf{% |
| 1102 |
hydrogThetaFile }and \textbf{hydrogSaltFile}. These files should contain 3D |
| 1103 |
data ordered in an (x, y, r) fashion with k=1 as the first vertical level. |
| 1104 |
If no file names are provided, the tracers are then initialized with the |
| 1105 |
values of \textbf{tRef }and \textbf{sRef }mentioned above (in the equation |
| 1106 |
of state section). In this case, the initial tracer data are uniform in x |
| 1107 |
and y for each depth level. |
| 1108 |
|
| 1109 |
\begin{itemize} |
| 1110 |
\item forcing |
| 1111 |
\end{itemize} |
| 1112 |
|
| 1113 |
This part is more relevant for the ocean, the procedure for the atmosphere |
| 1114 |
not being completely stabilized at the moment. |
| 1115 |
|
| 1116 |
A combination of fluxes data and relaxation terms can be used for driving |
| 1117 |
the tracer equations. \ For potential temperature, heat flux data (in W/m$% |
| 1118 |
^{2}$) can be stored in the 2D binary file \textbf{surfQfile}\textit{. }% |
| 1119 |
Alternatively or in addition, the forcing can be specified through a |
| 1120 |
relaxation term. The SST data to which the model surface temperatures are |
| 1121 |
restored to are supposed to be stored in the 2D binary file \textbf{% |
| 1122 |
thetaClimFile}\textit{. }The corresponding relaxation time scale coefficient |
| 1123 |
is set through the variable \textbf{tauThetaClimRelax}\textit{\ }(in s). The |
| 1124 |
same procedure applies for salinity with the variable names \textbf{EmPmRfile% |
| 1125 |
}\textit{, }\textbf{saltClimFile}\textit{, }and \textbf{tauSaltClimRelax}% |
| 1126 |
\textit{\ }for freshwater flux (in m/s) and surface salinity (in ppt) data |
| 1127 |
files and relaxation time scale coefficient (in s), respectively. Also for |
| 1128 |
salinity, if the CPP key \textbf{USE\_NATURAL\_BCS} is turned on, natural |
| 1129 |
boundary conditions are applied i.e. when computing the surface salinity |
| 1130 |
tendency, the freshwater flux is multiplied by the model surface salinity |
| 1131 |
instead of a constant salinity value. |
| 1132 |
|
| 1133 |
As for the other input files, the precision with which to read the data is |
| 1134 |
controlled by the variable \textbf{readBinaryPrec}. Time-dependent, periodic |
| 1135 |
forcing can be applied as well following the same procedure used for the |
| 1136 |
wind forcing data (see above). |
| 1137 |
|
| 1138 |
\begin{itemize} |
| 1139 |
\item dissipation |
| 1140 |
\end{itemize} |
| 1141 |
|
| 1142 |
Lateral eddy diffusivities for temperature and salinity/specific humidity |
| 1143 |
are specified through the variables \textbf{diffKhT }and \textbf{diffKhS }% |
| 1144 |
(in m$^{2}$/s). Vertical eddy diffusivities are specified through the |
| 1145 |
variables \textbf{diffKzT }and \textbf{diffKzS }(in m$^{2}$/s) for the ocean |
| 1146 |
and \textbf{diffKpT }and \textbf{diffKpS }(in Pa$^{2}$/s) for the |
| 1147 |
atmosphere. The vertical diffusive fluxes can be computed implicitly by |
| 1148 |
setting the logical variable \textbf{implicitDiffusion }to '.\texttt{TRUE}% |
| 1149 |
.'. In addition, biharmonic diffusivities can be specified as well through |
| 1150 |
the coefficients \textbf{diffK4T }and \textbf{diffK4S }(in m$^{4}$/s). Note |
| 1151 |
that the cosine power scaling (specified through \textbf{cosPower }- see the |
| 1152 |
momentum equations section) is applied to the tracer diffusivities |
| 1153 |
(Laplacian and biharmonic) as well. The Gent and McWilliams parameterization |
| 1154 |
for oceanic tracers is described in the package section. Finally, note that |
| 1155 |
tracers can be also subject to Fourier and Shapiro filtering (see the |
| 1156 |
corresponding section on these filters). |
| 1157 |
|
| 1158 |
\begin{itemize} |
| 1159 |
\item ocean convection |
| 1160 |
\end{itemize} |
| 1161 |
|
| 1162 |
Two options are available to parameterize ocean convection: one is to use |
| 1163 |
the convective adjustment scheme. In this case, you need to set the variable |
| 1164 |
\textbf{cadjFreq}, which represents the frequency (in s) with which the |
| 1165 |
adjustment algorithm is called, to a non-zero value (if set to a negative |
| 1166 |
value by the user, the model will set it to the tracer time step). The other |
| 1167 |
option is to parameterize convection with implicit vertical diffusion. To do |
| 1168 |
this, set the logical variable \textbf{implicitDiffusion }to '.\texttt{TRUE}% |
| 1169 |
.' and the real variable \textbf{ivdc\_kappa }to a value (in m$^{2}$/s) you |
| 1170 |
wish the tracer vertical diffusivities to have when mixing tracers |
| 1171 |
vertically due to static instabilities. Note that \textbf{cadjFreq }and |
| 1172 |
\textbf{ivdc\_kappa }can not both have non-zero value. |
| 1173 |
|
| 1174 |
\subsection{Simulation controls} |
| 1175 |
|
| 1176 |
The model ''clock'' is defined by the variable \textbf{deltaTClock }(in s) |
| 1177 |
which determines the IO frequencies and is used in tagging output. |
| 1178 |
Typically, you will set it to the tracer time step for accelerated runs |
| 1179 |
(otherwise it is simply set to the default time step \textbf{deltaT}). |
| 1180 |
Frequency of checkpointing and dumping of the model state are referenced to |
| 1181 |
this clock (see below). |
| 1182 |
|
| 1183 |
\begin{itemize} |
| 1184 |
\item run duration |
| 1185 |
\end{itemize} |
| 1186 |
|
| 1187 |
The beginning of a simulation is set by specifying a start time (in s) |
| 1188 |
through the real variable \textbf{startTime }or by specifying an initial |
| 1189 |
iteration number through the integer variable \textbf{nIter0}. If these |
| 1190 |
variables are set to nonzero values, the model will look for a ''pickup'' |
| 1191 |
file \textit{pickup.0000nIter0 }to restart the integration\textit{. }The end |
| 1192 |
of a simulation is set through the real variable \textbf{endTime }(in s). |
| 1193 |
Alternatively, you can specify instead the number of time steps to execute |
| 1194 |
through the integer variable \textbf{nTimeSteps}. |
| 1195 |
|
| 1196 |
\begin{itemize} |
| 1197 |
\item frequency of output |
| 1198 |
\end{itemize} |
| 1199 |
|
| 1200 |
Real variables defining frequencies (in s) with which output files are |
| 1201 |
written on disk need to be set up. \textbf{dumpFreq }controls the frequency |
| 1202 |
with which the instantaneous state of the model is saved. \textbf{chkPtFreq }% |
| 1203 |
and \textbf{pchkPtFreq }control the output frequency of rolling and |
| 1204 |
permanent checkpoint files, respectively. See section 1.5.1 Output files for the |
| 1205 |
definition of model state and checkpoint files. In addition, time-averaged |
| 1206 |
fields can be written out by setting the variable \textbf{taveFreq} (in s). |
| 1207 |
The precision with which to write the binary data is controlled by the |
| 1208 |
integer variable w\textbf{riteBinaryPrec }(set it to \texttt{32} or \texttt{% |
| 1209 |
64}). |
| 1210 |
|
| 1211 |
%%% Local Variables: |
| 1212 |
%%% mode: latex |
| 1213 |
%%% TeX-master: t |
| 1214 |
%%% End: |
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