MOM6 Bug Fixes - Nov 2023 to Jul 2024

[yichengt900]

Hi CEFI-regional-MOM6 modelers,

Below is a table summarizing the new bug fix flags added from November 2023 to July 2024 (Thanks @theresa-morrison). Users of regional MOM6 configurations under development can use this information to avoid issues related to the identified bugs.

Last Update: August 5, 2024 (WIP)

Flag	Default	Recommended	Pull Request	Notes
MASS_WEIGHT_IN_PGF_NONBOUS_BUG	False	False	PR 692	Only used in non-Boussinesq cases with MASS_WEIGHT_IN_PRESSURE_GRADIENT set to true
FRICTWORK_BUG	True	False	PR 663
[*]_USE_OM4_SUBCELLS	True	False	PR 662	There are many new parameters added with this suffix, all should be set to false
BACKSCATTER_UNDERBOUND	True	False	PR 656	Only applies when Lapalcian viscosity is negative (such as from backscatter)
VISC_REM_BUG	True	False	PR 639	This parameter controls the defaults of three individual flags, VISC_REM_TIMESTEP_FIX, VISC_REM_BT_WEIGHT_FIX, and VISC_REM_CONT_HVEL_FIX
MEKE_GM_SRC_ALT_SLOPE_BUG	True	False	PR 620	This parameter controls the defaults of three individual flags, VISC_REM_TIMESTEP_FIX, VISC_REM_BT_WEIGHT_FIX, and VISC_REM_CONT_HVEL_FIX
INIT_BOUNDARY_EXTRAP	False	True	PR 608	May only impact domains with ice cavities
HOR_DIFF_LIMIT_BUG	True	False	PR 585	If true and HOR_DIFF_ANSWER_DATE is 20240330 or below break symmetry
USE_CONT_THICKNESS	False		PR 579	See also PR 697
TRIG_CHANNEL_DRAG_WIDTHS	True		PR 543	SIf false, use a more accurate than the mathematically equivalent trigonometric version
UNSPLIT_DT_VISC_BUG	False	False	PR536	Replaces FIX_UNSPLIT_DT_VISC_BUG (was default true)
USTAR_GUSTLESS_BUG	False	False	PR535	Replaces FIX_USTAR_GUSTLESS_BUG (was default true)
USE_HUYNH_STENCIL_BUG	False	False

P.S. In MOM6, “bugs” can refer to incorrect code or mathematically equivalent code that fails rigorous tests (such as rotational testing). Consequently, while these flags might alter the results of a simulation, they might not affect the solution at all. To verify whether solutions agree or disagree across tests, it is recommended to compare the ocean.stats files.