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• Exodus file: "ne4.g".   This is a netcdf file following Exodus conventions.  It gives the corners of all elements on the sphere and their connectivity.  It is independent of the polynomial order used inside the element ("np").  

  • This file is used by TempestRemap (TR) to generate mapping files.  The polynomial order is a command line option and the GLL nodes are internally generated by TR.  

• latlon SCRIP file:  "ne4np4_latlonne4pg2.scrip.nc".   This file contains a list of all the GLL nodes in the mesh (in latitude/longitude coordinates).   The list of GLL nodes must be in the the internal HOMME global id ordering, matching the ordering used in CAM and EAM native grid output.   It also contains the connectivity of the GLL subcell grid.   

  • This file is used by CAM's interpic_new utility, and graphics programs Paraview and Visit when plotting native grid output.

  SCRIP file:description of the atmosphere physics grid n the format used by the original incremental remap tool SCRIP. It is used for most output and also used to generate mapping files between components and for post-processing of most output.

• Less common “GLL” metadata files needed for specialized purposes:

  • SCRIP file:  "ne4np4_scrip.nc".   This file contains a description (SCRIP format) of the GLL dual grid

  , in the format used by the original incremental remap tool SCRIP

  • .

   

  • It includes the locations of the GLL nodes and artificial bounding polygons around those nodes.   Ideally the spherical area of each polygon will match the GLL weight ("exact GLL areas"), but not all tools can achieve exact areas.  Inexact areas does not impact the accuracy of the resulting mapping algorithm, it just means that mass will not be exactly conserved by the mapping algorithm.  

    • Needed in E3SMv2 configurations by the cube_to_target topography dataset generation tool.

    • Historically used by

    CESM/

    • E3SMv1 to create ocean/atm mapping files (exact GLL areas are important here, to conserve fluxes)

    Used

    • Historically used by

    the

    • E3SMv1 for regional and sub-gridscale regridding post-processing tools ( https://acme-climate.atlassian.net/wiki/spaces/SIM/pages/754286611/Regridding+E3SM+Data+with+ncremap, http://nco.sf.net/nco.html#sgs)

  • latlon file:  "ne4np4_latlon.nc".   This file contains a list of all the GLL nodes in the mesh (in latitude/longitude coordinates).   The list of GLL nodes must be in the the internal HOMME global id ordering, matching the ordering used in CAM and EAM native grid output.   It also contains the connectivity of the GLL subcell grid.   

    • This file is used by CAM's interpic_new utility, and graphics programs Paraview and Visit when plotting native grid GLL output.

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Step-by-step guide

1. Generate a new "grid" file

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TempestRemap can now be pulled in with NCO via conda, or can be built from source from the Github repository. This is straightforward on Cori and Edison. Note that a parallel version of netCDF should be usedTo build from source, make sure a netCDF module is loaded. This can be accomplished on cori/edison be executing module swap cray-netcdf cray-netcdf-hdf5parallel or by sourcing an env_mach_specific.sh from a working case on the target machine before building. Then, 

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This will build TempestRemap into tempestremap/bin. For the rest of the tutorial, assume that the environment variable ${tempest_root} points to this directory (or where a conda-build of TempestRe:

tempest_root=${PWD}/tempestremap

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• land grid descriptor file in SCRIP format 

• ESMF_RegridWeightGen

• geographic distribution for each land surface type along with grid descriptor files for each of those surface types

• mkmapdata.sh (found in components/clm/tools/shared/mkmapdata/)

• mksurfdata.pl (found in components/clm/tools/clm4_5/mksurfdata_map/)

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