How to generate restarts for MOM6 coupled model ?

1 Atmosphere and Sea Ice Restart

Identify atmosphere and sea ice restarts, for e.g., /nfs3m/archive/sfa_cache04/users/g06/ehackert/GEOS5.0/eh025/restarts/Y2021/restarts.e20210630_00z.tar

If the file is archived, demigrate it:

dmget <path_to_file>/restarts.e20210630_00z.tar &

Once it is available, do following:

1. untar it.
2. Strip prefix

rename eh025. '' eh025.*

and suffix in names of restart files:

rename .e20210630_00z.Icarus-3_3_p2.a180x1080_o1440x1080.newtile_CF0180x6C_DE0360xPE0180.nc4 '' *.e20210630_00z.Icarus-3_3_p2.a180x1080_o1440x1080.newtile_CF0180x6C_DE0360xPE0180.nc4

2 cap_restart

Create a cap_restart that records the date of the restarts in the format (in one line):

yyyymmdd hhmmss

3 Run the Remap Restart Script

Run GEOSgcm/install/bin/remap_restarts.py from your build, or use following sample template.

Remap Restarts Package

Coupled model relevant restarts:

openwater_internal_rst - this file will be created with the remap restarts package

seaicethermo_internal_rst - this file will be created with the remap restarts package

seaice_internal_rst - this file will not be created with the remap restarts package

seaice_import_rst - this file will not be created with the remap restarts package

ocean_internal_rst - this file will not be created with the remap restarts package

RESTART/ - directory with MOM and CICE specific restart files. There is no (scientifically viable) way to remap them. User has to take them from somewhere. For MOM6, its restarts can be bootstrapped from WOA T and S climatology. WOA18 file can be found here: /discover/nobackup/projects/gmao/bcs_shared/make_bcs_inputs/ocean/MOM6/common/WOA18_decav_TPOTS_monthly_fulldepth_01.nc

These two files, seaice_internal_rst and seaice_import_rst, are on the ocean grid, so technically they are different from those surface restarts on tiles. If the user doesn't have these files they can easily be bootstrapped in the model setup.

ocean_internal_rst is also on the ocean grid. It can also be bootstrapped in the model setup. In the case of using the bootstrapped option to obtain this restart the user will require a longer time scale to spin it up.

#
# The remap restart package questionnaire will populate this template file, create remap_params.yaml. 
# This is a preferable option due to the frequent script changes. 
# It can be done manually; see the example below for MOM5 ICA C180 to MOM6 C12 NL3. 
# Note: In the example below, the user changes the `out_dir` path and `account.`
#

input:
  air:
    drymass: 1
    hydrostatic: 0
  shared:
    MERRA-2: false
    stretch: false
    # (coupled) ocean model: data, MOM5, MOM6
    omodel: MOM5
    agrid: C180
    bc_base: /discover/nobackup/projects/gmao/bcs_shared/fvInput/ExtData/esm/tiles
    bc_version: ICA
    expid: M2OCEAN_S2SV3
    ogrid: 1440x1080
    rst_dir: /discover/nobackup/projects/gmao/SIteam/Remapping_Test_Cases/s2sv3Toc12MOM6/inputs
    yyyymmddhh: '1982010100'
  surface:
    zoom: '2'
    wemin: '26'
    # it supports three models: catch, catchcnclm40, catchcnclm45
    catch_model: catch
    # if catch_tilefile is null, it searches bcs_dir
    catch_tilefile:
output:
  output:
  shared:
    label: true
    # SG001,SG002
    stretch: false
    # (coupled) ocean model: data, MOM5, MOM6
    omodel: MOM6
    agrid: C12
    bc_base: /discover/nobackup/projects/gmao/bcs_shared/fvInput/ExtData/esm/tiles
    bc_version: NL3
    expid: ''
    ogrid: 72x36
    out_dir: /discover/nobackup/$USER/remap_output
  air:
    # remap upper air or not
    remap: true
    nlevel: '72'
    agcm_import_rst: false
  surface:
    split_saltwater: true
    surflay: 50.
    wemin: '13'
    # remap lake, saltwater, landicet
    remap_water: true
    # remap catch(cn)
    remap_catch: true
    # if catch_tilefile is null, it searches bc_dir
    catch_tilefile:
    # the name of ease grid
    EASE_grid:
  analysis:
    bkg: false
    aqua: true
    lcv: false
slurm_pbs:
  account: Account number user is charging  
  qos: debug
  partition: ''

Be sure to:

• Set modules: source .../GEOSgcm/@env/g5_modules
• Use the ⬆️ template as .../GEOSgcm/install/bin/remap_restarts.py -c remap_params.yaml

4 Copy the Restart Files in the Experiment Directory

Once all (atmosphere and sea ice) restarts have been generated, copy them to the experiment location and run. If MOM6 ocean is starting from climatology, use this. Otherwise provide restarts and again, follow instructions provided here to properly configure.

Other MOM6 restart options