[MITgcm-support] exch2 and autogenerated grids (llc, cs, etc.)

[Ryan Abernathey]

Thanks for the reply. You cleared up one source of confusion: the grid
files are NOT generated by MITgcm. They need to be generated by the user.
(Correct?)

But I am still confused about one thing:
Where is the script that generates the input files for the llc
configurations?
If I could see the logic within this script, I feel like I could maybe
start to understand how the llc grid works.

-Ryan

On Thu, Oct 22, 2015 at 11:34 PM, Jean-Michel Campin <jmc at ocean.mit.edu>
wrote:

> Hi Ryan,
>
> There might be some confusion here:
> 1) this part of the documentation:
> > http://mitgcm.org/public/r2_manual/latest/online_documents/node233.html
>  is NOT up-to-date. No need to use any matlab script (driver.m) from
>  MITgcm/utils/exch2/matlab-topology-generator to set-up the
> correct/customized
>  exch2 topology. See the top of the 2 README files
>  in: utils/exch2/matlab-topology-generator and in: utils/exch2/code-mods
>
>  Setting SIZE.h and data.exch2 should be enough to get pkg/exch2
> tile-topology
>  set-up.
>  But this is (mostly) independent from the the input grid-files
>  which provides lat,lon position, grid-spacing and grid-cell area.
>
> 2) Regarding grid files (horizGridFile= ...) used with
> usingCurvilinearGrid=T,
>  I am not aware of any MITgcm fortran code that would generate these files.
>  Some set of grid-files are available (in some verification exp., also in
>  MITgcm_contrib area) but otherwise you will need to generate these files.
>  There has been few email exchange on support list related to how generate
>  grid-files for cubed-sphere grid ; and you can take a look at the recently
>  publish paper in GMD about ECCO-v4, with some information regarging the
>  lap-lon-cap grid and grid-files.
>
> Cheers,
> Jean-Michel
>
> On Thu, Oct 22, 2015 at 05:16:17PM -0400, Ryan Abernathey wrote:
> > Hi,
> >
> > After avoiding this issue for a long time, I am finally trying to
> > understand how the new auto-generated grids work (in particular the llc
> > grids).
> >
> > Is this documentation up to date?
> > http://mitgcm.org/public/r2_manual/latest/online_documents/node233.html
> >
> > For the global_oce_llc90 setup, the input files seem very simple, i.e.
> data
> > file just has
> >   usingCurvilinearGrid=.TRUE.,
> >
> > and data.exch2 has
> >   W2_printMsg= 0,
> >   W2_mapIO   = 1,
> >   preDefTopol=0,
> >   dimsFacets(1:10) = 90, 270, 90, 270, 90, 90, 270, 90, 270, 90,
> >   facetEdgeLink(1:4,1)= 3.4, 0. , 2.4, 5.1,
> >   facetEdgeLink(1:4,2)= 3.2, 0. , 4.2, 1.3,
> >   facetEdgeLink(1:4,3)= 5.4, 2.1, 4.4, 1.1,
> >   facetEdgeLink(1:4,4)= 5.2, 2.3, 0. , 3.3,
> >   facetEdgeLink(1:4,5)= 1.4, 4.1, 0. , 3.1,
> >
> > This is evidently enough information to completely specify the grid
> > geometry. But I can't figure out where in the code the geometry is
> actually
> > calculated. In ini_curvilinear_grid.F, it looks like it is just reading
> the
> > geometry from horizGridFile (i.e. tile.0001.mitgrid). So when do these
> > horizGridFiles get written?
> >
> > Just looking for some hints to get started on understanding this
> important
> > but intimidating subject.
> >
> > Thanks,
> > Ryan
>
> > _______________________________________________
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> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
>
>
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