Detailed Instructions

Downloading CESM with MOM6

MOM6 is now an optional ocean component in CESM 2.2, along with the primary ocean component POP2, which is to be deprecated in CESM 3.0. The following instructions describe how to download the experimental releases of CESM2.2 with MOM6.

Creating a new MOM6 case in CESM:

What's available

Grids:

• tx0.66v1 (workhorse): tripolar, 0.66-degree grid developed for MOM6+CESM.
• gx1v6 (testing only): dipole, 1-degree grid inherited from POP2.
• tx0.25v1 (testing only): tripolar, 0.24-degree grid from the MOM6 community.

Compsets:

Resolution:

When creating a new MOM6+CESM case, users need to specify the resolution

...

Machines:

• MOM6+CESM is routinely tested in the following NCAR machines:
• cheyenne (CISL)
• hobart (CGD)
• izumi (unified)

Running MOM6 cases:

Customizing MOM6 cases:

Understanding files located in the run directory:

The following table summarizes the main files associated with CESM/MOM6, which are located in the run directory (determined by xml variable RUNDIR). Files termed 'IN' are required input files, while files termed 'OUT' appear after the model has been run:

Input file	i/o	Contents	POP's Equivalent
input.nml	IN	Has the necessary fortran namelists for executing MOM6 and controlling non-MOM6 components of the code. This includes the list of MOM-style parameter files to read, usually "MOM_input" and "MOM_override". We rarely change this file in CESM/MOM6.	NA
MOM_input	IN	Contains all the necessary run-time parameters that define this experiment.	namelist_default
MOM_override	IN	Is usually blank except in cases where there are several variants on an example (e.g. with different coordinates).	user_nml_pop
diag_table	IN	List of diagnostics, used by FMS's diagnostic manager.	tavg_contents, tavg_nml
MOM_parameter_doc.all	OUT	Records all the run-time parameters that are not associated with the parallelization.	pop_in
MOM_parameter_doc.short	OUT	Records all the non-default run-time parameters that are not associated with the parallelization.	NA
MOM_parameter_doc.layout	OUT	Records all the run-time parameters that are associated with the parallelization. These parameters are computational and do not affect the numerical solution.	NA
available_diags	OUT	a list of available diagnostics for this particular configuration.	NA
ocean.stats.*	OUT	are ascii and netCDF files with a few key statistics/metrics used for bitwise regression testing by the core-MOM6 team.	$CASENAME.pop.dd
MOM_IC.nc	OUT	file containing the ocean initial conditions.	NA
ocean_geometry.nc	OUT	file describing the topography, Coriolis parameter, grid locations and various other fixed fields from the ocean grid.	NA
Vertical_coordinate.nc	OUT	file describing the variables associated with the vertical coordinate	NA
*.mom6.static.nc	OUT	file describing static variables of the ocean model (e.g., geolon, area, wet, etc). These variables are defined in the diag_table.	NA
*.mom6.sfc_*.nc	OUT	file showing daily means of surface variables of the ocean model (e.g., SST, SSS, SSU, etc). These variables are defined in the diag_table.	NA
*.mom6.frc_*.nc	OUT	file showing daily means of forcing fields of the ocean model (e.g., taux, sensible, evap, etc). These variables are defined in the diag_table.	NA
*.mom6.hm_*.nc	OUT	file showing monthly means of selected variables using the native grid. These variables are defined in the diag_table.	NA
*.mom6.h_*.nc	OUT	this is the ocean model history file used by the CESM postprocessing tool. Variables are defined in the diag_table.	NA
*.mom6.r.*.nc	OUT	ocean model restart file.	*.pop.r.*.nc

Modifying run-time parameters and adding new available diagnostics:

Go to the CASEROOT and create file SourceMods/src.mom/MOM_override. Add the following line to this file:

#override KH = 800.0 ! set background Laplacian horizontal viscosity to 800.0 m^2/s

Copy diag_table from RUNDIR into SourceMods/src.mom/. Edit this file by adding the following line to the list of monthly mean variables outputted in the native grid (i.e., below line # ocean_month, native grid):

"ocean_model","Khh","Khh","CASE.mom6.hm%4yr-%2mo","all","mean","none",2 Don't forget to replace CASE by your case name.

Rerun the model (./case.submit). Now go to RUNDIR and verify that the above changes have been made by visualizing the variable that you just added (Khh) from file *.mom6.hm_0001_01.nc