[MITgcm-devel] another bug in growth.F ?
Jinlun Zhang
zhang at apl.washington.edu
Tue Dec 5 12:17:33 EST 2006
Martin Losch wrote:
> Jinlun,
> thanks for your opinion. The thsice thermodynamics are basically
> Winton's (2000) model, but we have not yet fully sorted out the
> advection part.
> I have now a run47 with SEAICEadvScheme = 1 (1st order upwind, too
> smooth) and no flooding, and and another one (run48) which is just
> like run45 but with only a 1/10th of the snow fall, just to see what
> happens, see
> http://mitgcm.org/~mlosch/run47.png
> http://mitgcm.org/~mlosch/run48.png
> As expected is run47 closest to what we expect. But run48 is not too
> bad either, too little snow (of course) and as a consequence too
> little ice. So either there is too much snow/precip in the
> atmospheric forcing, or there is something not kosher in the snow
> parameterizations. As the problems are similar with thsice I would
> agree that the forcing may be the problem ... I have to try and find
> different precipitation fields.
Marin,
Yeah run47.png looks pretty good. The advection works ok. But I wonder
what ice advction you are using, 2nd order or 1st order? The one I
installed is 2nd order. Ideally, the snow advection should be exactly
the same as the ice advection so ice and snow won't devorce with each other.
It is not right with run48 that when the snow is turned off, ice is
gone. Some thing is wrong here.
>
>
> I have also made another observation: I tried to run the different
> thermodynamics without any dynamics in a 1D case. I expect (and JMC
> agrees with me) that for constant air temperature (say -30degC), ice
> thickness should grow until there is some equilibrium thickness, when
> the remaining heat flux out of the ocean is balanced by the diffusive
> flux of heat through the ice. I assume that the diffusion is
> controlled by "SEAICE_iceConduct" for seaice and kice for thsice. The
> equilibrium thickness can roughly be estimated by hequil =
> conductivity*(Tair-Twater)/heatflux.
> I have only succeded yet in reaching some equilibrium thickness with
> thsice (with an unrealistic value of kice=1e-6 instead of 2). For
> growth, this only works if I turn on some precipitation (snow).
> Without snow HEFF is completely independent of SEAICE_iceConduct,
> which I don't think is right.
I don't understand this equil. ice thickness )-:. As said above, without
snow-without ice thing or ice not working right without snow does not
make sense to me.You might want to check with Thorndike (199?) for a toy
model of equil. ice thickness.
Jinlun
>
> M.
>
> On 5 Dec 2006, at 03:39, Jinlun Zhang wrote:
>
>> Martin,
>>
>> I would vote run45.png for best performance except that the summer
>> ice is slightly overestimated. I would not vote run41.png because of
>> its weird snow distribution. The snow pattern should generally
>> follow the ice pattern (could mean a problem with ice advection). I
>> don't know why the snow gets so thick with run40.png, the precip
>> forcing could be way off. But obviously snow advection helps a lot.
>> Snow flooding, if it overestimates ice, then turn it off, not big
>> deal (since what we do is to make the fields look like
>> observations). As for thsice, I don't know what is going on. But for
>> any ice thermodynamics that involves ice salinity (if thsice uses
>> ice salinity), there might be a singularity in the formulation (I
>> had such feeling before, but I could be wrong).
>>
>> Jinlun
>>
>> Martin.Losch at awi.de wrote:
>>
>>> Oops, sorry, Jinlun. All the figures are in http://mitgcm.org/
>>> ~mlosch :
>>> http://mitgcm.org/~mlosch/run40.png
>>> http://mitgcm.org/~mlosch/run41.png
>>> http://mitgcm.org/~mlosch/run42.png
>>> http://mitgcm.org/~mlosch/run43.png
>>> http://mitgcm.org/~mlosch/run44.png
>>> http://mitgcm.org/~mlosch/run45.png
>>> http://mitgcm.org/~mlosch/run46.png
>>>
>>> M.
>>>
>>> Martin Losch
>>> Alfred Wegener Institute Postfach 120161, 27515 Bremerhaven,
>>> Germany; Tel./Fax: ++49(0471)4831-1872/1797
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: Jinlun Zhang <zhang at apl.washington.edu>
>>> Date: Monday, December 4, 2006 6:10 pm
>>> Subject: Re: [MITgcm-devel] another bug in growth.F ?
>>>
>>>
>>>> Hi Martin,
>>>>
>>>> Where do you put the figures? I only see netcdf files from the links.
>>>>
>>>> Jinlun
>>>>
>>>> Martin Losch wrote:
>>>>
>>>>
>>>>> More on seaice/thsice.
>>>>>
>>>>> I have put a few results of my 2deg experiment (to 80N), forced
>>>>
>>>> with
>>>>
>>>>> CORE (modified NCAR/NCEP reanalysis) climatology:
>>>>>
>>>>> http://mitgcm.org/~mlosch/run40
>>>>> http://mitgcm.org/~mlosch/run41
>>>>> http://mitgcm.org/~mlosch/run42
>>>>> http://mitgcm.org/~mlosch/run43
>>>>> http://mitgcm.org/~mlosch/run44
>>>>> http://mitgcm.org/~mlosch/run45
>>>>> http://mitgcm.org/~mlosch/run46
>>>>>
>>>>> runs 40,41,42,45 are with seaice and growth-thermodynamics, runs
>>>>> 43,44,46 with seaice+thsice. All netcdf files are 10day averages
>>>>
>>>> in
>>>>
>>>>> the 101st year of integration, except for run43, which crashes at
>>>>> some time in the 6th decade, so that the netcdf files contains
>>>>
>>>> the
>>>>
>>>>> 51st year. I use asynchronous timestepping
>>>>> (deltaTtracer=12h,deltaTmom=20min) for all runs. there are also
>>>>> figures with appropriate files name (run40.png, etc) showing
>>>>> effective snow and ice thickness and ice concentration in march
>>>>
>>>> and
>>>>
>>>>> august for the antarctic ocean. Details:
>>>>> run40, not advection of snow, flooding (also included grid.*
>>>>
>>>> files).
>>>>
>>>>> Here you see the strange snow patterns, where snow is as high as
>>>>
>>>> 160m
>>>>
>>>>> (not included in colorscale), and depresses the sea surface by as
>>>>> much as 160m*0.33.
>>>>> run41, advection of snow (scheme 2 for all variables): advection
>>>>> distributes the snow and thing look more physical
>>>>> run42, advection of snow (scheme 2 for all variables),
>>>>
>>>> flooding=true:
>>>>
>>>>> a lot less snow but much more ice, too much if you ask me.
>>>>> run45, advection of snow and flooding, but advection scheme 1 for
>>>>
>>>> all
>>>>
>>>>> variables: the different advection schemes makes the solution
>>>>> smoother, but not better, as expected.
>>>>> run43, with thsice as is in the repository (crashed during the
>>>>
>>>> 6th
>>>>
>>>>> decade, don't know why), this version of the code should probable
>>>>> vanish pretty soon? tiny concentrations/thicknesses at the ice
>>>>
>>>> margins> run44, with thsice and JMC's "new version" in
>>>> seaice_advdiff.F: too
>>>>
>>>>> be compared with run45. thsice leads to even more ice than the
>>>>> simpler thermodynamics of run45. Thickness is way too high
>>>>
>>>> (compare
>>>>
>>>>> with www.seaice.de), and in summer the Eastern Weddell Sea should
>>>>
>>>> be
>>>>
>>>>> almost ice free (only some ice along the Peninsula).
>>>>> run46, like run44, but flooding turn off (commented out in
>>>>> thsice_calc_thickn.F): the flooding algorithm has less of an
>>>>
>>>> impact
>>>>
>>>>> on the solution than for growth.
>>>>>
>>>>> For a comparision with observations of concentrations see
>>>>> www.seaice.de, eg. March15, 2006 (from AMSR-E):
>>>>> http://iup.physik.uni-
>>>>>
>>>> bremen.de:8084/amsredata/asi_daygrid_swath/l1a/
>>>>
>>>>> s6250/2006/mar/asi-s6250-20060314-v5_nic.png
>>>>> Aug15,2006
>>>>> http://iup.physik.uni-
>>>>>
>>>> bremen.de:8084/amsredata/asi_daygrid_swath/l1a/
>>>>
>>>>> s6250/2006/aug/asi-s6250-20060815-v5_nic.png
>>>>>
>>>>> same dates in 1999 from SSMI
>>>>> http://iup.physik.uni-bremen.de:8084/archive/south/ 1999/19990315.png
>>>>> http://iup.physik.uni-bremen.de:8084/archive/south/ 1999/19990815.png
>>>>>
>>>>> So, as far as I can see, the model produces first order
>>>>
>>>> distriubtions
>>>>
>>>>> in all cases with too much extend in summer, too much ice in
>>>>
>>>> general
>>>>
>>>>> and too much snow. Not too bad, but how much of this do we
>>>>
>>>> expect.
>>>>
>>>>> I'll go and consult with my trusty ice specialists. But maybe
>>>>
>>>> someone
>>>>
>>>>> on this list can comment too (Jinlun?)
>>>>>
>>>>> Martin
>>>>
--
Jinlun Zhang
Polar Science Center, Applied Physics Laboratory
University of Washington, 1013 NE 40th St, Seattle, WA 98105-6698
Phone: (206)-543-5569; Fax: (206)-616-3142
zhang at apl.washington.edu
http://psc.apl.washington.edu/pscweb2002/Staff/zhang/zhang.html
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