[MITgcm-devel] another bug in growth.F ?

Tue Dec 5 09:13:35 EST 2006

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.

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.

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