The time scale for restoring surface salinity

[Biswamoy Paul]

Dear MOM6 Community,
I am running MOM6+SIS2 for the Indian Ocean by restoring the surface salinity from monthly WOA13. I assume that the surface salinity is nudged monthly in this setup. However, I see a significant deviation in simulated surface salinity from WOA13, given that model is not being provided with any river data. I need to nudge the salinity with an even smaller time scale, say ten days. But I could not find any switch in MOM_input or other input files to change this nudging time scale. So I wonder whether this is possible to do. It would be helpful for me if anyone could identify this possibility, if any.

 

[kshedstrom@alaska_edu]

I don't know about surface restoring, but for the SPONGE code, MOM6 will read a 2-d fields of sponge weights. What is the name of the option to turn on the surface restoring? I would grep on that to find the code and the related options that go with it.

Is there some reason not to include the river inputs? For recent hindcasts, we are using the glofas runoff to provide a river input to MOM6.

 

[gmarques]

Make sure you enabled salinity restoring:

RESTORE_SALINITY = True ! [Boolean] default = False
! If true, the coupled driver will add a globally-balanced fresh-water flux that
! drives sea-surface salinity toward specified values.

Then, you need to set/adjust the following parameters:

FLUXCONST = 0.1667 ! [m day-1] default = 0.0
! The constant that relates the restoring surface fluxes to the relative surface
! anomalies (akin to a piston velocity). Note the non-MKS units.
SALT_RESTORE_FILE = "state_restore_tx0.66v1_20200616.nc" ! default = "salt_restore.nc"
! A file in which to find the surface salinity to use for restoring.
SALT_RESTORE_VARIABLE = "salt" ! default = "salt"
! The name of the surface salinity variable to read from SALT_RESTORE_FILE for
! restoring salinity.
SRESTORE_AS_SFLUX = True ! [Boolean] default = False
! If true, the restoring of salinity is applied as a salt flux instead of as a
! freshwater flux.
MAX_DELTA_SRESTORE = 5.0 ! [PSU or g kg-1] default = 999.0
! The maximum salinity difference used in restoring terms.

 

[waguiar]

Hello!
I am having a similar issue while running MOM6. I have 2 regional set-ups with different vertical resolutions ( 1 m dz at top and 5 m dz at top). I want to compare these simulations, but making sure the salinity restoring at surface works in the same way, independent of the thickness of the surface cells.
As an example, I ran a similar set of simulations before with MOM5 ( 1m dz at top and 5 m dz at top), in which I maintained the piston velocity equal between the simulations, but adjusted the restoring timescale (salt_restore_tscale) to be proportional to the thickness of the top cell in each simulation.
I noticed MOM6 does not have the restore timescale option anymore - is this now automatically calculated by the model based on the vertical grid?