Changed default eddy parameterization for isopycnic vertical coordinate

[matsbn]

Changed the default eddy parameterization for vcoord_type = isopyc_bulkml to the same that is currently default for vcoord_type = cntiso_hybrid.

The associated previous default namelist values for vcoord_type = isopyc_bulkml were:

EDANIS = .false.
EDDF2D = .false.
EDSPRS = .true.
RHSCTP = .false.
EGC = 0.85
EGMNDF = 100.
EGMXDF = 1500.
RHISCF = 0.

Note that EGC and EGMXDF had grid specific values and that EGMNDF and EGMXDF are dimensional parameters, here provided with unit m²s^-1. New default namelist values are:

EDANIS = .true.
EDDF2D = .true.
EDSPRS = .false.
RHSCTP = .true.
EGC = 3.0
EGMNDF = 1.
EGMXDF = 2500.
RHISCF = 0.5

[matsbn]

Looks fine to me.

I see that you now have "mks" as the default and "cgs" as the optional, but "cgs" is still the default in config_component.xml. Would it make sense to transition to "mks" as default for the NorESM2.3 release?

In my opinion, we should run some coupled tests (with interactive DMS at least) to verify climatological similarity, both with hybrid and isopycnic coordinate. Another thing missing is the ability to restart from a simulation with CGS units and continue with MKS units. Although a bit-reproducible restart is unlikely, I think it would be a useful functionality. I'm a bit pressed on time now, but will see if some progress on this can be made.

[TomasTorsvik]

We plan to make a release candidate tag for NorESM2.3 after merging this PR.

[JorgSchwinger]

Wouldn't it make sense then to have a check of such namelist options to ensure that the settings make sense, and abort (or issue a warning) if both EDSPRS and EDANIS = true?

[matsbn]

Just to understand this: What is the reason that some parameters (e.g. EGC) that were dependent on the grid resolution have the same value for all grids now?

Otherwise it looks fine to me.

I do not think the different tunings that have been used, particularly for EGC, for different grids are necessarily transferable with the new eddy parameterization. Fine-tuning must be done individually for each grid, but the current values are likely a good starting point.