62 z ale remapping

[nichannah]

This pull request will change results. The line that causes the change is:

src/ALE/MOM_regridding.F90 122

Without this conservation checks fail when there are lots of 'squashed' layers. In model coords these have thickness 1e-10, whereas the new grid uses 1e-3

[adcroft]

The changes to MOM_regridding lead to NaNs in several of the ALE tests. I think this is why I had set the default minimum to that value (for stability). Can you revert that default value and add a method setMinThickness that you can use from within the diagnostics to set it to the tiny value you need?

[adcroft]

Doh! There is a method already - setRegriddingMinimumThickness() which is how MOM_ALE.F90 sets it for the model at run-time.

[nichannah]

OK, thanks I have fixed that. I'm no longer getting any results (timestats) changes from master. I still don't completely understand why remapping conservation checks are failing when using minthickness of 1e-3).

[adcroft]

How about providing a method to associate h, instead of moving this call so far?

[nichannah]

Thanks for your comments, I've fixed those things. There's one thing I'm not sure about. I've changed the grid definition config to be like:

DIAG_REMAP_Z_GRID_DEF = "FILE:," e.g.
DIAG_REMAP_Z_GRID_DEF = "FILE:OM3_zgrid.nc,zw"

This means that when we move to other vertical coords there will need to be another config e.g.:

DIAG_REMAP_SIGMA_GRID_DEF = "FILE:OM3_sigmagrid.nc,si"

Also if we want to use a generated grid, can do:
DIAG_REMAP_Z_GRID_DEF = "UNIFORM:"

I'm not sure if this is what you had in mind.

[adcroft]

@nicjhan That's exactly what I had in mind.