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The NCAR CSM

Climatological Data Ice Model

Version 4.0

1998 © UCAR/NCAR


User's Guide

Brian Kauffman, kauff @ ucar.edu

Introduction

The Climatological Data Ice Model (dice) functions as the sea ice component in a CSM configuration. Recall that a configuration consists of various independent component models (e.g. atmosphere, land, ocean, sea-ice), each connected to a flux coupler. This sea ice model component interacts with the CSM Flux Coupler just like any ice model would, but it is not an active model, rather, it takes SST data from an input data file, infers an ice extent, and sends this data 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" ice model is useful for seeing how an active atmosphere component behaves when coupled to climatological ice extent.

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.

Contents
 §1  Input data
 §2  Output data
 §3  Input parameters
 §4  Preparing the model for execution
 §5  Source code maintenance

1   Input data

SST data

The ice model state variable ice fraction (equivalently, ice extent) is derived from input 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) on a global 2x2 degree grid. A file is provided (bundled with the source code distribution) 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.

Note: if CSM configuration consists of a dummy ocean and a dummy ice model (e.g. coupled to active atmosphere and land models), normally one would coordinate the ice model's SST data with the ocean model's SST data so that the SST's and ice extent were consistent.

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

This model receives the following fields from the flux coupler (via message passing): Normally none of these fields are used by this model. These fields are received because the coupler/ice 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.

2   Output data

History files

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

Restart files

Normally this model does not need or create restart files. There are exceptions, however: restart files will be created if any of the input parameters flux_uv, flux_Qacc, or flux_swpf (see below) have been reset from their default values. Restart files are in a machine dependent binary format. If users want to examine the contents of a restart file, they will have to look at the source code to see how it was created and write their own program to read the file and examine it's contents.

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

This model sends the following fields to the flux coupler (via message passing): This model must send these fields to the coupler because this is part of the coupler/ice interface requirement. The coupler has no way of knowing whether the components it is connected to are active models or data models.

How the output fields are derived

3   Input parameters

The model reads an input namelist from stdin at runtime. Following is a list and description of available namelist input parameters.
case_name
Type: character
Default: "null"
Required: no, and only used if restart files are necessary (see above), ignored otherwise
Description: This is the case name text string, up to 8 characters, which is included in output files to help identify the model run.

case_desc
Type: character
Default: "null"
Required: no, and only used if restart files are necessary (see above), ignored otherwise
Description: This is a short text string, up to 80 characters, which is included in output files to help identify the model run.

rest_type
Type: character
Default: "initial"
Required: only when restart files are necessary (see above), ignored otherwise
Description: This selects the run type. Valid choices are: "initial," "continue," "branch," "regenerate." Selecting "branch" or "regenerate" makes rest_bfile a required input.

rest_dir
Type: character
Default: "null"
Required: only when restart files are necessary (see above), ignored otherwise
Description: This is a mass store directory name. Restart and history files go into this directory. For continuation or regeneration runs, the initial condition restart file must also be in this directory.

rest_bfile
Type: character
Default: "null"
Required: only when restart files are necessary (see above) and rest_type = "branch" or "regeneration," ignored otherwise
Description: This is the name of a restart file (on the mass store) which will provide the IC's for a branch or regeneration run.

rest_pfile
Type: character
Default: "null"
Required: only when restart files are necessary (see above), ignored otherwise
Description: This is the complete path and name of the restart pointer file. The path must specify an existing, NFS mounted directory.

ncpl
Type: integer
Default: 24
Required: no (assuming the default value is appropriate)
Description: This specifies how many times per day the model communicates (exchanges data) with the coupler

flux_Qacc
Type: integer
Default: 0 ( 0 <=> false)
Required: no
Description: If flux_Qacc .ne. 0 (i.e. true, accumulation is activated), accumulate ice formed in the ocean if Q > 0, and melt any accumulated ice if Q < 0. Note: the melt rate won't exceed (a) the rate that would melt all accumulated ice in one communication interval, or (b) the maximum melt rate specified by flux_Qmin.

flux_Qacc0
Type: real
Default: 0.0 (kg)
Required: no (only used if flux_Qacc .ne. 0)
Description: On an initial run, the accumulated water mass field is initialized to this value.

flux_Qmin
Type: real
Default: -1000.0 (kg/s/m²)
Required: no (only used if flux_Qacc .ne. 0)
Description: The melt rate is limited by flux_Qmin (recall fluxes are positive down). This prevents a potentially unreasonable melt rates.

info_dbug
Type: integer
Default: 1
Required: no
Description: Debugging information level: 0, 1, 2, or 3.
  • 0 => write the least amount of debugging information to stdout
  • 1 => write a small amount of debugging information to stdout
  • 2 => write a medium amount of debugging information to stdout
  • 3 => write a large amount of debugging information to stdout

4   Preparing the model for execution

The model's setup script, called ice.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 (dice4 climatological data ice 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 ice ) then
     echo 'Note: using an existing binary'
     ls -lFt ice src/Build.log.* | head
   else 
     #--- 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/ice/dice4.0    "  >! 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
     end
   
     #--- select resolution ---
     rm -f dims.h ; ln -s dims.h.150x111 dims.h
   
     #--- create make's include files & invoke make ---
     Makeprep                        >>& $BLDLOG
     make EXEC=dice4 ARCH=$ARCH      >>& $BLDLOG || exit 2
   
     #--- link binary into /. directory ---
     cd ..
     rm -f ice ; ln -s src/dice4 ice
   endif 
   
   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/ice/dice4.0
   cp -fp $DATADIR/*.nc  .
   rm data.sst.nc    ; ln -s  sst.str.nc         data.sst.nc
   rm data.domain.nc ; ln -s  domain.150x111.nc  data.domain.nc
   
   cat >! ice.parm << EOF
     &inparm
     ncpl = 24
     /
   EOF
   
   echo "o contents of ice.parm:" ; cat ice.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
o identifying a source code directory (directories),
o acquiring the source code from that directory (directories),
o selecting a resolution-dependent "dims.h" file,
o executing the Makeprep script which creates the include files required by the makefile (e.g. a list of dependencies), and
o executing the Makefile.

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

Here an input data file directory is specified, the data files found in that directory are copied into the working directory (note they are all netCDF files), and the desired input files are linked to the file names "data.sst.nc" and "data.domain.nc" (the model expects files by these names to exist in the working directory). Next an input namelist file is constructed. See the section describing the input namelist variables for more details.

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.