[MITgcm-devel] ICE workshop - recap and homework!

[Gael Forget]

Hi Martin et al,

I am moving some of the "ICE workshop - recap and homework!" thread that followed from the MIT ice workshop to devel list.

> Further, for checking the conservation properties in my configuration it would be helpful if Gael could provide a data.diagnostics.
Will follow.

> About the seaice defaults: I am not clear about the turbulent flux formulae. The implementation that I updated to today requires that I set
> #define MCPHEE_OCEAN_ICE_HEAT_FLUX
> #define GRADIENT_MIXED_LAYER_TURBULENCE_FACTOR
> Do we need to set anything else in data.seaice in order to get the agreed parameter set?
I know it's confusing even for me at this point. It took me a while to figure out a more of less adequate way (see below)
of unifying the various flavours of this term's specification that had been added over the years. I mostly hope that this 
merge keeps non-specialists of pkg/seaice from overlooking default changes when they update their copy of MITgcm.

Below I give explanations  and guidelines (correct ones I hope) for using the new run time parameters.
I do the same for SEAICE_MULTICATEGORY and SEAICE_VARIABLE_FREEZING_POINT.
That information is also in SEAICE_PARAMS.h and/or seaice_check.F and/or in the standard output.

Cheers,
Gael

old def/undef SEAICE_VARIABLE_FREEZING_POINT : now unified way of specifying sea water freezing 
point. So it should always be defined and the rest is done with run time params. Changed default.
-----------------------------------------------------------------------------------------
old default : SEAICE_tempFrz0 = -1.96, SEAICE_dTempFrz_dS = 0.
new default : SEAICE_tempFrz0 = 0.0901, SEAICE_dTempFrz_dS = -0.0575
?? do we have a precise reference for 0.0901 + S * SEAICE_dTempFrz_dS ??


def/undef SEAICE_MULTICATEGORY : no change to default. So use CPP as before.
But added run time switch : set SEAICE_multDim to 1 or 7, regardless of CPP. It is assumed 
that user provide pickup accordingly, as before. Pickup code will likely need consolidation.
---------------------------------------------------------------------------------------------------------


old def/undef MCPHEE_OCEAN_ICE_HEAT_FLUX & GRADIENT_MIXED_LAYER_TURBULENCE_FACTOR : 
now unified way of specifying the turb. ocean-ice flux. So the CPPs should always be defined and the rest is
done with run time params. Old run time params can still be used. Changed default.
----------------------------------------------------------------------------------------------------------------------------
defaults etc :
-- old default    : SEAICE_mcPheePiston = drf(1)/SEAICE_deltaTtherm, SEAICE_frazilFrac=1., SEAICE_mcPheeTaper=0.,
-- new default    : SEAICE_mcPheePiston = 0.000875, SEAICE_frazilFrac=1., SEAICE_mcPheeTaper=0.,
-- baseline params : SEAICE_mcPheePiston = 0.000875, SEAICE_frazilFrac=1., SEAICE_mcPheeTaper=0.92,
-- old mcphee cpp : SEAICE_mcPheePiston = 0.000875, SEAICE_frazilFrac=0., SEAICE_mcPheeTaper=0.92,
-- SEAICE_mcPheeStepFunc always false (old GRADIENT_MIXED_LAYER_TURBULENCE_FACTOR).
conversions of old to new params :
-- SEAICE_mcPheePiston = dRf(kSurface)/SEAICE_gamma_t
-- SEAICE_frazilFrac = SEAICE_deltaTtherm/SEAICE_gamma_t_frz
-- SEAICE_mcPheePiston = SEAICE_availHeatFrac * dRf(kSurface)/SEAICE_deltaTtherm
-- SEAICE_frazilFrac = SEAICE_availHeatFracFrz
?? do we have a precise reference for 0.000875 and 0.92 ??