[MITgcm-support] NETCDF files not Coards compliant

[Ed Hill]

On Thu, 2005-03-17 at 14:33 -0600, Dierk Polzin wrote:
> 
> The netcdf files generated by the MITgcm do not seem to be Coard
> compliant..
> and cannot be opened cleanly in 
> GRADS
> FERRET
> PANOPLY
> etc..
> only ncview will open them.. 
> I believe they need "latitude and longitude and better definitions and
> units on all parameters.
> 
> Is anyone working on fixing the netcdf files or should I work on a
> local solution.
> 
> state.0000.000001.nc


Hi Dierk,

Yes, we're aware that the NetCDF files currently generated by MITgcm are
not "strictly compliant" with either COARDS or CF -- though they are
valid NetCDF and they do work with many NetCDF post-processing tools.

And yes, we would like to move towards CF compliance:

  http://www.cgd.ucar.edu/cms/eaton/cf-metadata/index.html

But please be aware that, in some important cases (eg. cubesphere), the
MITgcm grids are not aligned with any Lat/Lon coordinate system.  This
means that they are not amenable to the simple COARDS conventions (or,
for that matter, many existing NetCDF pre-/post-processing tools) which
*implicitly* assume grid alignment with some Lat/Lon coordinate system:

  http://ferret.wrc.noaa.gov/noaa_coop/coop_cdf_profile.html

The newer CF convention does allow for more general grids

  http://www.cgd.ucar.edu/cms/eaton/cf-metadata/CF-1.0.html#grid_ex2

but it is not fully supported by all the tools that traditionally use
NetCDF files.

So, I'd be glad to work with you to improve our CF compliance.  And
hopefully that will make the MITgcm output work better with your
favorite pre- and post-processing tools.

Ed

-- 
Edward H. Hill III, PhD
office:  MIT Dept. of EAPS;  Rm 54-1424;  77 Massachusetts Ave.
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