Page Comparison

See also CAM-FV Grid Overview and ATM Grid Resolution Summary

CAM-SE works with data stored at Gauss-Lobatto-Legendre (GLL) nodes.  These nodes can be interpreted in several ways shown in various grids below.  In the "SE native grid", "SE subcell grid" and "SE dual grid", the GLL nodes are the same (the green dots in the figure).   Internally, the dycore uses the CAM-SE native grid connectivity, but the rest of CAM and E3SM has no knowledge of the grid connectivity and only sees data at GLL nodes and their associated area weight.  The other other types of connectivity are not used within the model, but are sometimes used by pre- and post-processing tools.

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1. TempestRemap:  https://github.com/ClimateGlobalChange/tempestremap.   
   1. Used to make Exodus files (GLL and physgrid) and to make SCRIP files (physgrid only).
   2. Used to make mapping files for GLL grids directly from the Exodus file.
2. Obsolete:  For quasi-uniform cubed-sphere grids, E3SM currently uses the "pentagons" option to construct the dual grid for making ESMF mapping files.  To create these meta data grid files,  we use a utility distributed with the E3SM code - see e3sm/components/homme/test/tool.
3. Obsolete:  For RRM grids, E3SM v1 used the "cheveron" option to construct the dual grid for making ESMF mapping files.  To create these meta data grid files we use a Matlab program that performs a Newton interation.  This matlab code is in the E3SM PreAndPostProcessingScripts repo under regridding/spectral_elements_grid_utilities/

Using TempestRemap to create Exodus and SCRIP files: 

1. To create the Exodus file.  For cubed sphere grids with a resolution of "NE":  
   1. GenerateCSMesh --alt --res $NE --file ne${NE}.g
   2. For RRM grids, the Exodus .g file is part of the model configuration and is stored along with the initial condition files in the E3SM input data server, inputdata/atm/cam/inic/homme
2. To create a SCRIP file for PG2 grids from the Exodus file:
   1. GenerateVolumetricMesh --in ne${NE}.g --out ne${NE}pg2.g --np 2 --uniform 2
   2. ConvertExodusToSCRIP --in ne${NE}pg2.g  --out ne${NE}pg2.scrip.nc
3. For E3SM V2, the physics is running on the "PG2" grid.  This means most output, and all coupled model mapping files need to work with PG2 grids.   
   1. Mapping files should be created using the SCRIP file 

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