enable cpl_scalars in coupled model for CSG and regional domains

[DeniseWorthen]

Description

One of the most powerful features of the CMEPS mediator is the capabilty to write out mediator history files. These history files are a fundamental tool for diagnosing the fields exchanged between components. They are enabled either at the component level via config or by enabling a special mediator phase for history writing. See Discussion #934 for details.

CMEPS uses a scalar field within the exportState of a component to determine how to decompose the internal CMEPS fields, which are on a mesh, into the 2-d fields of structured grid component. This currently is enabled for MOM6, CICE6 and WW3 (when on a structured grid). For FV3, the capability currently exists through a work-around which allows the setting of a config variable for the cube-sphere tile size. This does not work for regional grids however. Without having the ATM exchange fields on the tiles, mediator history files need to be post-processed to create fields which can be visualized. This is cumbersome and makes the history files more difficult to use.

Solution

Add the required cpl_scalars export to FV3. This will enable an additional index in the cpl_scalars array which will contain the number of tiles, either 6 for the CSG or 1 for the regional, and the nx,ny size of each tile. A similar method can also be used for NoahMP.

Modify CMEPS to recognize the additional index in the cpl_scalars and, when non-zero, use the index to set the number of 2-d domains to write in the history files.

Add the required config variables to ufs.configure. These will be of the form

      ScalarFieldCount = 3
      ScalarFieldIdxGridNX = 1
      ScalarFieldIdxGridNY = 2
      ScalarFieldIdxGridNTile = 3
      ScalarFieldName = cpl_scalars

This will place the number of tiles into the third index of the cpl_scalar array, which will allow CMEPS to write CSG or single tile FV3 or NoahMP history files decomposed into the required number of tiles.

Alternatives

Related to