CESM Models

CESM Models: CSM1.4 Climatological Data Ocean Model User's Guide


Authored by: Brian Kauffman kauff @ ucar.edu


The Climatological Data Ocean Model (docn) functions as the ocean component in a CSM configuration. Recall that a configuration consists of various independent component models (atmosphere, land, ocean, and sea-ice), each connected to a flux coupler. The docn ocean component interacts with the flux coupler just like any ocean model would, but it is not an active model, rather, it takes SST data from an input data file and sends it to the coupler, ignoring any forcing data received from the coupler. Typically the input data file contains climatological SST data (e.g. from Shea, Trenberth, & Reynolds). Such a "dummy model" is useful for coupling an active atmosphere model with climatological SST data.

Important Note: When assembling a CSM configuration, carefully consider the limitations and requirements of all components and be sure that the complete set of component models will interact in a meaningful way. In particular, consider whether the data provided by this model is adequate for your application.


1. Input Data

SST Data

On startup, this model reads in SST data from a netCDF file. This file, is called data.sst.nc, contains 12 months of SST data (presumably monthly mean fields), and is on a 2x2 degree grid. A file is provided with the source code that can be used in this context. This file contains Shea, Trenberth, & Reynolds (STR) SST climatology data. The file provided can be replaced by any other SST data file that is in the same format. Because netCDF files are self describing, one can query the file itself for specifics about the file format.

Model domain

On startup, this model reads in domain data from a netCDF file. Data exchanged with the coupler will be on this model domain. This file, called data.domain.nc, contains x & y coordinate arrays as well as a domain mask. This model uses a latitude/longitude grid only, with 1d coordinate arrays x(i) & y(j), and a 2d domain mask mask(i,j). A mask value of 0 indicates land points (i.e. not in the model's domain) and negative values indicate land-locked regions (e.g. the Caspian Sea).

Input parameter namelist

On startup, this model reads an input namelist parameter file from stdin. This model has very few input namelist parameters. Often times there will be only one input parameter, ncpl, which is a positive integer specifying how many times per simulated day this model will communicate with the flux coupler. See the section on input namelist variables for a complete list and description of namelist parameters.

Data received from the flux coupler

The model receives the following fields from the flux coupler (via message passing):

None of these fields are used by this model. These fields are received because the coupler/ocean interface specification requires that this set of fields be received. The coupler has no way of knowing whether the components it is connected to are active models or data models.

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2. Output data

History files

This model does not create history files. The only data associated with this model is the data that is already contained in the input SST data file.

Restart files

This model does not need or create restart files.

Runtime diagnostics

This model generates some diagnostic messages which are written to stdout. This output consists mostly of brief messages that indicate how the simulation is progressing and whether any error conditions have been detected. Stdout also contains a record of the values of all model input parameters.

Data sent to the flux coupler

The model sends the following fields to the flux coupler (via message passing):

While the SST is taken from the input data file (based on the 12 monthly average fields, linearly interpolated in time), the remaining fields are set to zero. This model must send these fields to the coupler because this is part of the coupler/ocean interface requirement. The fields are set to zero because we must assume they be used by the coupler (or perhaps another component model) and it would seem that zero values are reasonable in this context. The coupler has no way of knowing whether the components it is connected to are active models or data models.

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3. Input Parameters

The model reads an input namelist from stdin at runtime. Following is a list and description of available namelist input parameters.


Default: 1
Required: no (assuming the default value is appropriate)
Description: This specifies how many times per day the model communicates (exchanges data) with the coupler


Type: integer
Default: 1
Required: no
Description: Debugging information level: 0, 1, 2, or 3.

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4. Preparing the model for execution

The model's setup script, call ocn.setup.csh, is invoked prior to the execution of the model. The setup script builds the executable code, documents the source code, and gathers the required input data files.

Each CSM component gets it's own, separate subdirectory in which it's setup script is run, in which the it's executable resides, and in which all of it's input and output files are kept. A set of environment variables set in a parent NQS script and is available for use (a model may not actually use all of these variables).

Below is an example setup script, followed by some explanation.

   #! /bin/csh -f 
   # Purpose:
   #  (a) build an executable model (docn4 climatological data ocn model)
   #  (b) document the source code used
   #  (c) gather or create necessary input files 

   echo '================================================================='
   echo ' Preparing model for execution                                   '
   echo '================================================================='
   echo ' '
   echo Date: `date`
   echo ' '
   echo 'Env variables by a parent shell:'
   echo '  $CASE     = ' $CASE
   echo '  $CASESTR  = ' $CASESTR
   echo '  $RUNTYPE  = ' $RUNTYPE
   echo '  $ARCH     = ' $ARCH
   echo '  $CSMSHARE = ' $CSMSHARE
   echo '  $MAXCPUS  = ' $MAXCPUS
   echo '  $SSD      = ' $SSD
   echo '  $MSS      = ' $MSS
   echo '  $MSSDIR   = ' $MSSDIR
   echo '  $MSSRPD   = ' $MSSRPD
   echo '  $MSSPWD   = ' $MSSPWD
   echo '  $RPTDIR   = ' $RPTDIR
   echo '  $MSGLIB   = ' $MSGLIB
   echo '-----------------------------------------------------------------'
   echo ' (a) Build an executable                                         '
   echo '-----------------------------------------------------------------'
   if ( -e ocn ) then
     echo 'Note: using an existing binary'
     ls -lFt ocn src/Build.log.* | head
     #--- create a src code sub-directory ---
     mkdir src
     cd src
     #--- document the build ---
     set BLDLOG = Build.log."`date +%y%m%d-%H%M%S`"
     echo 'Note: (re)building a binary'
     echo "See: $BLDLOG   "
     echo "Build log      "      >!  $BLDLOG
     echo "Date: `date`   "      >>& $BLDLOG
     echo "Dir : `pwd`    "      >>& $BLDLOG
     echo "User: $LOGNAME "      >>& $BLDLOG
     #--- gather source code ---
     echo "/fs/cgd/csm/models/ocn/docn4.0    "  >! Filepath
     #cho "/insert/filepath/for/patches      "  >> Filepath
     foreach SRCDIR (`cat Filepath`)
       echo "o gathering src code from $SRCDIR" >>& $BLDLOG
       cat $SRCDIR/README                       >>& $BLDLOG
       ls -lF $SRCDIR                           >>& $BLDLOG
       cp -fp $SRCDIR/* .                       >>& $BLDLOG
     #--- select resolution ---
     rm -f dims.h ; ln -s dims.h.ncom_x2 dims.h
     #--- create make's include files & invoke make ---
     Makeprep                        >>& $BLDLOG
     make EXEC=docn4 ARCH=$ARCH      >>& $BLDLOG || exit 2
     #--- link binary into /. directory ---
     cd ..
     rm -f ocn ; ln -s src/docn4 ocn
   echo '-----------------------------------------------------------------'
   echo ' (b) document the source code used                               '
   echo '-----------------------------------------------------------------'
   echo "o contents of /src:"      ; ls -alFt   src        ; echo ' '
   echo "o revision control info:" ; grep 'CVS' src/*.[hF] ; echo ' '
   echo '-----------------------------------------------------------------'
   echo ' (c) gather or create necessary input files                      '
   echo '-----------------------------------------------------------------'
   set DATADIR = /fs/cgd/csm/models/ocn/docn4.0
   cp -fp $DATADIR/*.nc  .
   rm data.sst.nc    ; ln -s  sst.str.nc           data.sst.nc
   rm data.domain.nc ; ln -s  domain.ncom_x2_1.nc  data.domain.nc
   cat >! ocn.parm << EOF
     ncpl = 1
   echo "o contents of ocn.parm:" ; cat ocn.parm ; echo ' '
   echo "o contents of `pwd`:"    ; ls -alF      ; echo ' '
   echo '================================================================='
   echo ' End of setup shell script                                       '
   echo '================================================================='

Items (a) through (c) in the above setup script are now reviewed.

(a) Build an executable

The goal here is to build an executable binary in the current working directory. This is done by

The model resolution (i.e. the number of x and y grid points) must be known at compile time and is specified in one resolution-dependent file: dims.h. Notice how an appropriate dims.h file is selected. Several dims.h files are provided corresponding to frequently used resolutions, but it is easy to create a dims.h file for any desired resolution. The details of how to build the executable (e.g. preprocessor and compiler options) are contained in the Makefile.

(b) Document the source code used

Here we make a detailed listing of the source code used, a list of revision control system (CVS) information, and list of the contents of the current working directory. This information can be used to identify the source code used in a particular simulation.

(c) Gather or create necessary input files

An input namelist file is constructed. The namelist variables specify how often the model will communicate with the coupler (12 times per day) and what the input land data sequence will be (three years of data, starting at year five, with the first year in the data sequence corresponding with simulation year one). See the section describing the input namelist variables for more details.

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5. Source Code Maintenance

The distribution Fortran source code for this model comes with a Makefile which suitable for use Cray C90, Cray J90, SGI, or NEC SX4 architectures. By examining how compilation between these various machines is handled, it should be easy to port this code to other machines as well. The code is written almost entirely using standard Fortran 77.

The code must be compiled with a particular model resolution in mind. The only files that must change with respect to resolution (i.e. have "hard-coded" resolution dependence) are dims.h (a source code file) and data.domain (an input data file). See the section describing the setup script for an example on how these dependencies are handled at compile time and run time.

This code was developed using the CVS revision control system, but only one "tagged" version of the code is available within any one distribution. Each source code file contains detailed revision control information.

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