Glossary

supergrid

A MOM6 supergrid contains the grid metrics and the areas at twice the nominal resolution of the actual computational grid. During runtime, MOM6 reads in the supergrid file, and then decomposes the supergrid into the four staggered grids, each containing different sets of prognostic variables, e.g., tracers, velocities, etc.

tripolar grid

A grid with three poles instead of one, typically with two of the three poles displaced into Northern Hemisphere land masses so that no singularity falls within the ocean domain. Commonly used for global MOM6 configurations. mom6_forge can modify but not yet create tripolar grids from scratch.

displaced pole grid

A grid in which a single pole is moved off of the true geographic pole and into a land mass, avoiding a singularity within the ocean domain without the added complexity of a tripolar grid.

ESMF mesh

An unstructured-mesh NetCDF file format (produced by Topo.write_esmf_mesh) used by the NUOPC coupler in CESM to acquire grid and land/ocean mask information for a component. Most functions in Regridding & Mapping operate on ESMF mesh files rather than raw longitude/latitude arrays.

SCRIP grid

An older NetCDF grid description format used by the SCRIP regridding library. Superseded by ESMF mesh files for most purposes in modern CESM, but still required to generate ocean-runoff mapping files (see Regridding & Mapping). Written by Topo.write_scrip_grid.

CICE grid

The grid file format expected by the CICE sea ice model, describing the same horizontal grid as the MOM6 supergrid and topography files. Written by Topo.write_cice_grid when a configuration includes a CICE component.

Cressman interpolation

A distance-weighted interpolation scheme in which source points within a smoothing radius contribute to a destination value with weight decreasing as a function of distance. Used by mom6_forge (see Regridding & Mapping) to fill bathymetry from a coarser source dataset without letting nearby land elevations contaminate coastal ocean depths.

TOPO_CONFIG

A MOM6 runtime parameter (set in MOM_input) selecting an idealized bathymetry shape, such as flat, bowl, or spoon. The Topo class’s set_flat, set_bowl, and set_spoon methods produce bathymetry matching these same idealized configurations.

channel width constraint

An effective width override for a strait or channel that is too narrow to be resolved at the model’s grid resolution but still needs to permit flow. Managed by ChannelWidth/ChannelWidthList and applied on top of the bathymetry at runtime, independently of the depth/mask fields themselves.