[MITgcm-support] netcdf with curvilinear grid

[Martin Losch]

Hi Ed and others,

sorry to hear that I kept you up so long. That was not my intention.  
Hope you are asleep now and others pick up for you (o:

And now I have to tell you, that the problem is not really in the  
netcdf files. The problem is that my screwy configuration with a  
curvilinear grid does not have "proper" coordinate variables (in  
netcdf speak), so that programs like ncview or gluemnc, that use  
coordinate variables to display/arrange individual tiles give funny  
results.

I would suggest to modify mnc, so that in the case of  
"usingCurviLinearGrid=.TRUE." (and without exch2), the coordinate  
variables X and Y become simply the grid indices, as it is done for  
the cube sphere/llc configurations (which do use exch2). Could you  
point me to the places/files where this should be done and I'll try  
to do that.

Martin


On 31 Jan 2008, at 10:08, Ed Hill wrote:

> On Thu, 31 Jan 2008 08:34:30 +0100 Martin Losch wrote:
>>
>> where in the jungle of mnc can I find a clue of what's happening,
>> why for one tile/cpu, the j-ordering is one way and for the other
>> it's reversed, what variables control that and where do they get
>> their information from, so I can try to hunt this problem down.
>
>
> Hi Martin,
>
> Its 4am here.  I've already spent a long day coding and then looked
> through MNC and MITgcm files just because you asked so *very*
> politely.
>
> I don't understand your problem.  Perhaps its lack of sleep.  But here
> are some observations:
>
>  0) The "gridfiles.tar" you sent is not a complete setup.  I
>     don't have the foggiest idea what topology (EXCH1 or EXCH2)
>     you are trying to use since you very helpfully omitted all
>     the input files or code that specify that information.
>
>  1) When you think about the grids keep in mind that MNC does
>     not (anywhere!) "flip" or permute the grid quantities
>     during either reads or writes to the netcdf files.  The
>     netcdf files always have the same "orientation" in memory
>     within MITgcm as they do on disk -- just the addition
>     or removal of points around the halo regions.
>
>     The only thing like "flipping" that MNC does is the storage
>     of the tile edge-edge coincidence information as provided by
>     either "EXCH1" or EXCH2.  You can use:
>
>       cd pkg/mnc
>       grep -i exch *.F
>
>     to see where these occur within MNC.  And note that this
>     "flipping" does not permute anything *within* the per-tile
>     files.  It just specifies how the tiles are "sewn" together.
>
>  2) Have you looked at the code in the following files:
>
>       model/src/ini_curvilinear_grid.F
>       pkg/exch2/w2_e2setup.F  (if using EXCH2)
>
>     and convinced yourself that things have the same order within
>     the *.mitgrid files that the code expects?  Its a very good
>     place to start.
>
>
> Ed
>
> -- 
> Edward H. Hill III, PhD  |  ed at eh3.com  |  http://eh3.com/
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