Hello all, I am looking for the best approach to describe in a CF compliant way the tripolar grids usually used in NEMO configurations.
Basically, the difference with a usual bipolar grid (north pole-south pole) is that the north pole is split into 2 poles moved over Canada and Russia (to have distortions/singularities not over the ocean). A good visual representation can be found here: http://www.geomar.de/typo3temp/pics/globe_grid2_14_b8edb639ae.png everything south of the green line (40degN) is identical to a regular grid, but everything north of it is computed using a technique described here: Madec, G. and M. Imbard, 1996 : A global ocean mesh to overcome the north pole singularity. Clim. Dyn., 12, 381–388. The usual NEMO output of the grid looks like this: float longitude(y, x) ; longitude:standard_name = "longitude" ; longitude:units = "degrees_east" ; longitude:long_name = "longitude" ; float latitude(y, x) ; latitude:standard_name = "latitude" ; latitude:units = "degrees_north" ; latitude:long_name = "latitude" ; Basically both latitudes and longitudes need to be specified for each grid point, hence lat and lon are 2D arrays. This is not a problem itself but I would like to give more information through maybe grid_mapping or crs so it is clear that the grid is tripolar. This is useful information if one want to project/interpolate this back to a more regular representation. Looking at the CF conventions, I can see that grids can be fairly nicely documented but nothing for tripolar grids. Is there some documentation/guidelines on how to derive a proper grid_mapping/crs with valid attributes for tripolar grids? I would also like to add to my netcdf file a way to better describe axes: double y(y) ; y:units = "1" ; y:long_name = "j-index of mesh grid" ; y:standard_name = ??? ; double x(x) ; x:units = "1" ; x:long_name = "i-index of mesh grid" ; x:standard_name = ??? ; what would be the standard name of these? Thanks, ____________________________________ Dr. Sébastien Villaume Analyst ECMWF Shinfield Park, Reading RG2 9AX, UK +44 7825 521592 sebastien.villa...@ecmwf.int ____________________________________ _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata