MOM6 parameter changes for 0.4.0 #274

dougiesquire · 2025-02-17T05:13:29Z

With the updated version of MOM6 in the recently released ACCESS-OM3 0.4.0, there are a number of new bug fixes and recommended settings. These default to values that preserve answers and so are not used unless explicitly turned on in MOM_input. However, the CICE and CDEPS/CMEPS updates in ACCESS-OM3 0.4.0 broke reproducibility with 0.3.1 so there's no real value in using MOM6 settings that preserve MOM6 answers. Instead, we should move to these recommended settings:

EQN_OF_STATE = "WRIGHT_REDUCED" ! default = "WRIGHT"
                                ! EQN_OF_STATE determines which ocean equation of state should be used.
                                ! Currently, the valid choices are "LINEAR", "UNESCO", "JACKETT_MCD", "WRIGHT",
                                ! "WRIGHT_REDUCED", "WRIGHT_FULL", "NEMO", "ROQUET_RHO", "ROQUET_SPV" and
                                ! "TEOS10".  This is only used if USE_EOS is true.

Justification: GFDL to main (2024-05-31) mom-ocean/MOM6#1631 (comment)

VISC_REM_BUG = False            !   [Boolean] default = True
                                ! If true, visc_rem_[uv] in split mode is incorrectly calculated or accounted
                                ! for in two places. This parameter controls the defaults of two individual
                                ! flags, VISC_REM_TIMESTEP_BUG in MOM_dynamics_split_RK2(b) and
                                ! VISC_REM_BT_WEIGHT_BUG in MOM_barotropic.

Justification: see parameter description

BACKSCATTER_UNDERBOUND = False  !   [Boolean] default = True
                                ! If true, the bounds on the biharmonic viscosity are allowed to increase where
                                ! the Laplacian viscosity is negative (due to backscatter parameterizations)
                                ! beyond the largest timestep-dependent stable values of biharmonic viscosity
                                ! when no Laplacian viscosity is applied.  The default is true for historical
                                ! reasons, but this option probably should not be used because it can contribute
                                ! to numerical instabilities.

Justification: see parameter description

FRICTWORK_BUG = False           !   [Boolean] default = True
                                ! If true, retain an answer-changing bug in calculating the FrictWork, which
                                ! cancels the h in thickness flux and the h at velocity point. This isnot
                                ! recommended.

Justification: see parameter description

REMAPPING_USE_OM4_SUBCELLS = False !   [Boolean] default = True
                                ! This selects the remapping algorithm used in OM4 that does not use the full
                                ! reconstruction for the top- and lower-most sub-layers, but instead assumes
                                ! they are always vanished (untrue) and so just uses their edge values. We
                                ! recommend setting this option to false.

Z_INIT_REMAPPING_USE_OM4_SUBCELLS = False !   [Boolean] default = True
                                ! If true, use the OM4 remapping-via-subcells algorithm for initialization. See
                                ! REMAPPING_USE_OM4_SUBCELLS for more details. We recommend setting this option
                                ! to false.

DIAG_REMAPPING_USE_OM4_SUBCELLS = False !   [Boolean] default = True
                                ! If true, use the OM4 remapping-via-subcells algorithm for diagnostics. See
                                ! REMAPPING_USE_OM4_SUBCELLS for details. We recommend setting this option to
                                ! false.

EBT_REMAPPING_USE_OM4_SUBCELLS = False !   [Boolean] default = True
                                ! If true, use the OM4 remapping-via-subcells algorithm for calculating EBT
                                ! structure. See REMAPPING_USE_OM4_SUBCELLS for details. We recommend setting
                                ! this option to false.

INTWAVE_REMAPPING_USE_OM4_SUBCELLS = False !   [Boolean] default = True
                                ! If true, use the OM4 remapping-via-subcells algorithm for calculating EBT
                                ! structure. See REMAPPING_USE_OM4_SUBCELLS for details. We recommend setting
                                ! this option to false.

HBD_REMAPPING_USE_OM4_SUBCELLS = False !   [Boolean] default = True
                                ! If true, use the OM4 remapping-via-subcells algorithm for horizontal boundary
                                ! diffusion. See REMAPPING_USE_OM4_SUBCELLS for details. We recommend setting
                                ! this option to false.

Justification: see parameter description

I'll start with a PR to the dev-1deg_jra55do_ryf branch, then will cherry-pick into the open PRs for dev-1deg_jra55do_iaf, dev-1deg_jra55do_ryf_wombatlite and dev-025deg_jra55do_ryf

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dougiesquire · 2025-02-17T10:25:36Z

Note, we have also been defaulting to:

TIDE_USE_SAL_SCALAR = True      !   [Boolean] default = True
                                ! If true and TIDES is true, use the scalar approximation when calculating
                                ! self-attraction and loading.

and setting

TIDE_SAL_SCALAR_VALUE = 0.094   !   [m m-1]
                                ! The constant of proportionality between sea surface height (really it should
                                ! be bottom pressure) anomalies and bottom geopotential anomalies. This is only
                                ! used if TIDES and TIDE_USE_SAL_SCALAR are true.

However, these have now been deprecated (see NOAA-GFDL/MOM6#382).

The replacement parameters take default values equal to what we were using, so we can just use the defaults:

SAL_SCALAR_APPROX = True        !   [Boolean] default = True
                                ! If true, use the scalar approximation to calculate self-attraction and
                                ! loading.
SAL_SCALAR_VALUE = 0.094        !   [m m-1] default = 0.094
                                ! The constant of proportionality between sea surface height (really it should
                                ! be bottom pressure) anomalies and bottom geopotential anomalies. This is only
                                ! used if USE_SAL_SCALAR is true or USE_PREVIOUS_TIDES is true.

See COSIMA/access-om3#274

dougiesquire · 2025-02-17T23:53:08Z

@minghangli-uni also suggested:

AUTO_MASKTABLE = True           !   [Boolean] default = False
                                ! Turn on automatic mask table generation to eliminate land blocks.

This is currently set in our 0.25deg config, but not the 1deg configs

See COSIMA/access-om3#274

…ion (#169) * License file * Update incorrect note in MOM_override See COSIMA/access-om3#251 Co-authored-by: minghangli-uni <[email protected]> * Add non-default from MOM_parameter_doc.layout in the middle reorder MOM_input to follow MOM_parameter_doc.short Put non-default values from MOM_parameter_doc.debugging at the top Co-authored-by: Dougie Squire <[email protected]> * Add WIND_STAGGER to MOM_INPUT for clarity This only affects the logging, the actual value is hardcoded through a #ifdef CESMCOUPLED * Change atm and ice mesh from 1deg -> 025deg Change ice_ntasks to be 96 Remove unused components payu-org/payu#496 Removed some checks in Payu which required unused components to be present in the nuopc.runconfig file. Co-authored-by: Dougie Squire <[email protected]> * Update to ACCESS-NRI/ACCESS-OM3 deployment 25.01.0 * Update field dictionary with latest from CMEPS * add_gusts parameter needed for 0.4.0 build * Update nuopc.runconfig to turn-off dates in restart_pointers * Turn on netcdf4 per COSIMA/access-om3#81 The new build uses openmpi4.1.7, which fixes some bugs preventing parallel reads over symlinks. This allows use of parallelio netcdf4 option, even though at this resolution for most components we will still only use one PE for IO. * Use .d and .m in CICE history output filenames Per COSIMA/access-om3#201 * Turn off extra cice restarts and remove non functioning write_restart_at_endofrun per COSIMA/access-om3#175 * Set Earth radius the same as the UM * Update MOM6 parameters and docs See COSIMA/access-om3#274 --------- Co-authored-by: anton-seaice <[email protected]> Co-authored-by: Dougie Squire <[email protected]> Co-authored-by: Anton Steketee <[email protected]> Co-authored-by: dougiesquire <[email protected]>

See COSIMA/access-om3#274

dougiesquire · 2025-02-19T09:28:53Z

Closing as these changes have now been implemented in all dev- configs

aekiss · 2025-02-24T05:31:38Z

The replacement parameters take default values equal to what we were using, so we can just use the defaults:

SAL_SCALAR_APPROX = True        !   [Boolean] default = True
                                ! If true, use the scalar approximation to calculate self-attraction and
                                ! loading.
SAL_SCALAR_VALUE = 0.094        !   [m m-1] default = 0.094
                                ! The constant of proportionality between sea surface height (really it should
                                ! be bottom pressure) anomalies and bottom geopotential anomalies. This is only
                                ! used if USE_SAL_SCALAR is true or USE_PREVIOUS_TIDES is true.

Looks likeSAL_SCALAR_APPROX will default to false now we've disabled tides
https://github.com/mom-ocean/MOM6/blob/e818ea4e792f0b85797247f955789b3c1210db8d/src/parameterizations/lateral/MOM_self_attr_load.F90#L190

dougiesquire · 2025-02-24T05:42:56Z

Yeah, sorry that comment was written before we disabled tides. Thanks for clarifying.

dougiesquire self-assigned this Feb 17, 2025

dougiesquire added mom6 Related to MOM6 all_configurations priority:high labels Feb 17, 2025

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Additional MOM6 parameter changes for 0.4.0 ACCESS-NRI/access-om3-configs#176

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Cherry-pick 0.4.0 release related changes into 0.25deg ryf configuration ACCESS-NRI/access-om3-configs#169

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MOM6 parameter changes for 0.4.0 #274

MOM6 parameter changes for 0.4.0 #274

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MOM6 parameter changes for 0.4.0 #274

MOM6 parameter changes for 0.4.0 #274

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