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5.   Gridspec implementations

There are two pioneering implementations of the Mosaic Gridspec. One is a complete XML schema developed on the basis of the Gridspec; the other is a complete netCDF-3 implementation.

5.1.   The GENIE Gridspec

The GENIE project has the objective of building a Grid-based Earth system model that will built out of component models drawn from various sites across the Grid. Component models will be on their own grid mosaics; the Gridspec will be used to generate custom coupler and regridding code on the basis of the PRISM/OASIS coupler using the BFG (Dahl 1982).

The implementation was done completely in XML. To quote the GENIE Gridspec,

The gridspec has been implemented as an XML schema in preference to NetCDF to fit in with the XML metadata implementation used by BFG; eventually the gridspec should be available in both NetCDF/CF and XML formats, making it accessible to a wide range of Earth system modelling tools and programs.

Indeed, the second implementation cited here uses the netCDF-3 specification of the Gridspec.

5.2.   The GFDL implementation

The GFDL Earth system models have long used the exchange grid (Balaji et al. 2006b) as a means of flexible transfer between model components on independent grids. The exchange grid can be expensive to compute, and so has always been pre-computed and stored as a netCDF file within GFDL. As we expand the scope of our models to include mosaics (for instance, a cubed-sphere atmospheric model), it has become necessary to revise the grid specification. It was in the process of this revision that the Mosaic Gridspec was devised.

The Mosaic Gridspec 0.2 specification is currently being deployed in GFDL production codes that couple an atmosphere on a cube_sphere_grid, an ocean and a sea-ice model on a tripolar_grid, and a land model on a lat_lon_grid. The same Gridspec is also used for transformations of saved data between the various grids.

A complete suite of netCDF files expressing this gridspec, and a set of C programs for generating these, are being made available through Balaji’s grid page.

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