[MITgcm-devel] Add sea ice surface forcing to pkg/seaice

[Menemenlis, Dimitris (3248)]

Jean-Michel, I had a look at pkg/thsice treatment of snowPrecip (also before introducing snowPrecip in pkg/seaice) and my impression was that the existing treatment of snow in pkg/seaice is not quite right.  Specifically, pkg/thsice accounts for latent heat contribution of snow over open ocean while pkg/seaice did not.  In this (latent-heat-contribution-to-open-ocean) sense, the treatment of snowPrecip just introduced in pkg/seaice is more consistent with pkg/thsice than is the previous treatment of snow in pkg/seaice.

I am happy to leave things as is, code-wise, for time being.  What's there is sufficient for the latent-heat+freshwater input application that I have in mind.  But I would prefer if this component were to be tested as we go forward, at least so that I know when behavior is changed.  I agree, however, that global_ocean.cs32x15 (input.seaice + ad tests) is not a good place to test pkg/seaice snowPrecip.  It's best to test with a verification experiment that has SEAICE_VARIABLE_SALINITY defined.

Would it be OK if I added snowPrecip to "verification/seaice_obcs"?  Either as an addition to existing baseline experiment, which would change output.txt, or with an additional "input.snow" experiment?

Regarding your point b) below, I fully agree that we should aim to relegate pkg/seaice thermodynamics to the list of "Somebody That I Used To Know".  The Hibler 2-category model was supposed to be a simpler (and at the time we naively thought easier-to-adjoint) place holder for the Winton thermodynamics.  As a historical footnote, I attach a page from a 12-year-old NASA proposal that Jinlun and I worked on, which resulted in pkg/seaice.  In particular, look at comments highlighted in yellow.  It is embarrassing — and an indication of my naiveté and programming incompetence — that, 12 years later, (i) we have not yet achieved all the objectives listed in that proposal and (ii) we are still using the Hibler 2-category thermodynamics.

Dimitris Menemenlis

On Apr 24, 2012, at 8:30 AM, Jean-Michel Campin wrote:

> Hi Dimitris,
> 
> I think I already answered this by writing the following:
>> Point (iii) to (v) are even more confusing to me.
> 
> Fine with me to stay with the code as it is now, as long as:
> a) things are clear (clarification below).
> b) I can put the "snowprecipFile" business into the list of
>  "other reason to use pkg/thsice (instead of pkg/seaice thermo)"
> c) we don't turn on snowprecipFile in experiment global_ocean.cs32x15 
>  (input.seaice + ad tests).
> 
> clarification:
> 1) we know how to implement snowPrecip, whether it's specified
>  through snowprecipFile or inferred for precip & atemp/tsurf
>  (cf pkg/thsice).
> 2) however a different route has been taken in seaice_growth.F
>  in order to squeeze in ice from iceberg into snow precip.
> 
> Note regarding point (2): by thsice standard, it would be called a bug, 
> but in pkg/seaice, it's not so clear according to your list of 
> remarks from yesterday, (i) to (v), which left me confused.
> 
> Cheers,
> Jean-Michel

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