Extra CESM Case Information

Extra CESM Case Information#

Available Compset Aliases#

Regional compsets are available by checking out the CROCODILE-CESM/CESM fork. You can always use the long names of the compsets instead.

The only job of the %REGIONAL flag on MOM6 in the compset longnames below is to set an xml variable MOM6_DOMAIN_TYPE=REGIONAL, which shifts input parameters to regional defaults.

Alias

Long name

Description

CR_JRA

1850_DATM%JRA_SLND_SICE_MOM6%REGIONAL_SROF_SGLC_SWAV

Standalone ocean with data atmosphere from JRA

CR1850MARBL_JRA

1850_DATM%JRA_SLND_SICE_MOM6%REGIONAL%MARBL-BIO_SROF_SGLC_SWAV

ocean coupled with MARBL BGC model with data atmosphere from JRA

CR_JRA_GLOFAS

1850_DATM%JRA_SLND_SICE_MOM6%REGIONAL_DROF%GLOFAS_SGLC_SWAV

Standalone ocean with data atmosphere from JRA and data runoff from GLOFAS

CR1850MARBL_JRA_GLOFAS

1850_DATM%JRA_SLND_SICE_MOM6%REGIONAL%MARBL-BIO_DROF%GLOFAS_SGLC_SWAV

ocean coupled with MARBL BGC model with data atmosphere from JRA and data runoff from GLOFAS

GR_JRA

1850_DATM%JRA_SLND_CICE_MOM6%REGIONAL_SROF_SGLC_SWAV

ocean coupled with CICE sea ice model with data atmosphere from JRA

GR1850MARBL_JRA

1850_DATM%JRA_SLND_CICE_MOM6%REGIONAL%MARBL-BIO_SROF_SGLC_SWAV

ocean coupled with MARBL BGC model and CICE sea ice model with data atmosphere from JRA

GR_JRA_GLOFAS

1850_DATM%JRA_SLND_CICE_MOM6%REGIONAL_DROF%GLOFAS_SGLC_SWAV

ocean coupled with CICE sea ice model with data atmosphere from JRA and data runoff from GLOFAS

GR1850MARBL_JRA_GLOFAS

1850_DATM%JRA_SLND_CICE_MOM6%REGIONAL%MARBL-BIO_DROF%GLOFAS_SGLC_SWAV

ocean coupled with MARBL BGC model and CICE sea ice model with data atmosphere from JRA and data runoff from GLOFAS

Input Parameters#

MOM6 behavior is controlled through parameter files (namelists) and the diagnostic table. CrocoDash uses CESM’s MOM_interface to generate these files with sensible defaults.

Generated Files#

When you run case preview (or setup), CESM generates several MOM6 configuration files:

  • MOM_input - Main namelist controlling MOM6 parameters

  • diag_table - Diagnostic output configuration

  • others

These files are initially placed in the case’s CaseDocs directory for reference.

How Defaults Are Generated#

  1. MOM_interface - CESM’s bridge component for MOM6

    • Located in: components/mom in CESM sandboxes

    • Generates default files based on grid and component settings

    • Files generated via preview_namelists() which calls MOM_interface to validate and generate files

  2. Default Recommendations - CrocoDash (and the %REGIONAL compset) provides tested defaults

    • Grid-aware settings (domain size, resolution)

    • Physics settings appropriate for regional domains

    • Diagnostic settings for common use cases

Customizing Parameters#

There are two approaches to customizing MOM6 parameters:

1. User Namelist Modifications (What you should use!)#

Override specific parameters using user_nl_mom:

# In your case directory user_nl_mom 
DT_BAROCLINIC = 1800  ! Change timestep
TIDES = TRUE  ! Enable tides (internal)

Then regenerate namelists:

./preview_namelists

Advantages:

  • Clean, trackable changes

  • Easy to see what you modified

  • Plays well with CESM workflows

  • Can be included in case scripts

Viewing/Verifying Generated Files#

After running preview_namelists, check:

# View generated defaults
cat CaseDocs/MOM_input
cat CaseDocs/diag_table

# View your modifications
cat user_nl_mom
cat SourceMods/src.mom/MOM_input  # if using SourceMods

Common Customizations#

Change Model Timestep#

echo "DT_BAROCLINIC = 1800" >> user_nl_mom

Adjust Diagnostic Output Frequency#

Edit diag_table to change output intervals or variables.

For detailed information about MOM6 parameters:

  • MOM6 Manual: https://mom6.readthedocs.io/

  • MOM6 Parameters: MOM_input file comments and MOM6 documentation

  • CESM MOM_interface: See CESM documentation for default coupling parameters

Integration with CrocoDash#

When using CrocoDash, parameter customization happens after case creation:

  1. CrocoDash creates the case and adjusts parameters with grid and forcing configurations

  2. You customize parameters beyond CrocoDash via user_nl_mom or SourceMods

  3. You build and run the case with modified parameters

For configuration of forcing-specific parameters (tides, BGC, rivers, etc.), see Forcing Configuration instead.

Tips and Best Practices#

  • Start with defaults - CrocoDash provides tested defaults; modify only what you need

  • Document your changes - Add comments to user_nl_mom explaining why you changed things

  • Check compatibility - Some parameters interact; changing one may require changing others

You do not need to rebuild your case with parameter changes!!!

Contents