Exchange messages interpolation

[aaronjridley]

Description

In the cubesphere grid, the ghostcells don't line up when they go on to a different face. The old way of dealing with this was to put the ghostcells at the location of the cells on the other face. This does not work for the gradient calculator or the advection scheme, which assumes that the cells all line up along constant lines, and can be projected onto the same flat cube face. So, instead, the cells from the other face are interpolated to the location of the ghostcells on the current face. This seems to work for some faces, but doesn't seem to be exact. This needs to be investigated more at a later time.

Type of change

• Bug fix - in order to work with the gradient calculator and advection scheme, this needed to be fixed.

How Has This Been Tested?

The latitude and longitude are message passed in the test and are verified to be in the same location in the ghostcells.

Test configuration

• Operating system: Mac OSX 13.6
• Compiler, version number: gcc version 13.2

Checklist:

• [N/A] Make sure you are merging into the develop (not master) branch
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• [N/A] Add a note to CHANGELOG.md, summarizing the changes