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

[Patrick Heimbach]

Dimitris,

how about also looking at this video (contrasting to yours):
http://uashome.alaska.edu/~jmamundson/research.html

Visual inspection suggest icebergs with freeboards of at least 5 to 10 meters, 
and whose subsurface expression is therefore poorly captured by pkg/seaice.
I second Martin's skepticism…

-Patrick



On Apr 23, 2012, at 4:08 PM, Jean-Michel Campin wrote:

> Hi Dimitris,
> 
> In reverse order:
> let's separate the real modifications related to snowPrecip 
> and the cleaning issue (adding DIAGNOSTICS_IS_ON or constant setting), 
> since mixing both is going to be painful to trace back changes.
> 
> My question 2.b is not stupid, because snowPrecip (when specified
> from a file) can fall over open ocean (whereas with empty snowPrecipFile,
> it only snows when some ice is present).
> 
> And regarding 2.a: I think we know how snow accumulates:
> If snow is falling at a rate of 1.cm per hour, I expect afer 1 hour
> to have the actual snow thickness to have increased by 1.cm
> (and not by 1000 time more in the case where the area is 10^-3).
> 
> Cheers,
> Jean-Michel
> 
> On Mon, Apr 23, 2012 at 06:32:05PM +0000, Menemenlis, Dimitris (3248) wrote:
>> Jean-Michel, thank you for looking at this.
>> 
>> I don't want to waste too much of your, Gael's, or Martin's time with this
>> so I will check in a version of seaice_growth.F that does the same thing
>> but does not change the verification results.  The code is slightly
>> longer (and uglier?) than Revision 1.166, but I think OK until more
>> folks start using snowPrecip as input for pkg/seaice.
>> 
>> Answers to your comments below:
>> 
>> 1) lab_sea.hb87 seems very sensitive to truncation errors.
>> Even before latest changes to seaice_growth, it fails on my laptop.
>> 
>> I am interested in those two conditions:
>>> a) if the seaice-fraction is small (e.g., 10^-3), and a snow storm
>>> pass by, will all the snow pile up over this little ice fraction ?
>>> b) snow over fully open ocean grid-cell ?
>> so I made sure that they give reasonable-loking results.
>> Snow over fully open ocean grid does what we expect it to do, i.e.,
>> cool the ocean surface through negative latent heat release and then,
>> when SST reaches the freezing point, it starts growing "fresh" ice, provided
>> SEAICE_VARIABLE_SALINITY and SEAICEuseFlooding are defined.
>> The sea ice fraction (AREA) is initially small, but it very quickly grows
>> to reasonable-looking values.  Since we don't know how the ice
>> concentration should grow in open ocean during a snow storm,
>> I think that default behavior is OK for now.  The most important
>> feature is the negative latent heat release, which is modeled
>> with sufficient accuracy irrespective of sea ice fraction.
>> 
>> I tried to do this:
>>> c) less urgent: heat conservation and heat budget diagnostics ?
>>> Would be good to clarify point 2.a before updating the results
>>> (in case seaice_growth.F needs to be changed again).
>> correctly, but a second pair of eyes on this would not hurt.
>> With version 1.167 of seaice_growth.F, all the stuff pertaining
>> to snowPrecip will be contained within
>> "IF ( snowPrecipFile .NE. ' ' ) THEN, ..., ENDIF"
>> so if there is issues with heat conservation,
>> they will be restricted to the specific case of snowPrecip.
>> 
>> Finally, I notice that:
>> 1) seaice_growth.F does a lot of diagnostic computations, whether they are needed or not.
>> Shouldn't these computations be contained within
>> IF ( DIAGNOSTICS_IS_ON('????????',myThid) ) THEN, ..., ENDIF
>> statements?
>> 2) seaice_growth.F contains lots of constants, e.g., "0.0 _d 0", etc., which could be
>> replaced with parameters "ZERO", etc., from SEAICE_PARAMS.h
>> Happy to take care of either of these two changes, if requested to do so.
>> 
>> Dimitris Menemenlis
>> 
>> On Apr 23, 2012, at 6:12 AM, Jean-Michel Campin wrote:
>> 
>>> Hi Dimitris and others,
>>> 
>>> few things:
>>> 1) my impression (after a quick look at your changes) is that 
>>> with empty snowprecipFile, it's only truncation error changes.
>>> But still 2 fwd exp are failing (global_ocean.cs32x15.seaice & lab_sea.hb87
>>> since the criteria on baudelaire with gfortran is 13 digits) 
>>> which would require to update the output.
>>> Regarding AD tests, seems OK, don't see any new "fail".
>>> 
>>> 2) I don't have time now to check the case where snowprecip is specified
>>> (+ little time I have is spent checking which testreport output changes)
>>> and I don't know much about seaice_growth.F ; Can someone (Gael, Dimitris, 
>>> Martin, ...) check what does snowprecip do in the current seaice_growth.F ?
>>> In particular:
>>> a) if the seaice-fraction is small (e.g., 10^-3), and a snow storm
>>> pass by, will all the snow pile up over this little ice fraction ?
>>> b) snow over fully open ocean grid-cell ?
>>> c) less urgent: heat conservation and heat budget diagnostics ?
>>> Would be good to clarify point 2.a before updating the results
>>> (in case seaice_growth.F needs to be changed again).
>>> 
>>> Cheers,
>>> Jean-Michel
>> 
>> 
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