Questions about USE_GRID_SPACE_DIAGNOSTIC_AXES

[kshedstrom@alaska_edu]

I had this option off originally, but tried turning it on assuming it might save time if I'm in Z* coordinates, writing out in z. Is this true?

It was working, though I didn't check the timing, but now it is no longer working. I wasn't checking for each MOM6 update, so I could figure out when it broke with some effort. Do we care about this working?

 

[andrew-c-ross]

I think the issue may have come from lines 412 and 414 of MOM_diag_mediator.F90, which pass the optional position argument if USE_GRID_SPACE_DIAGNOSTIC_AXES is True, but below they are not passed if it's False. If so it's an easy fix.

It may have been affected by this commit, since that's what last made significant changes to these lines.

Also making things worse, this flag is tested by setting it to True in tc0, but tc0 has an empty diag_table so I don't think the code gets exercised.

 

[kshedstrom@alaska_edu]

In thinking over the timing, it is far more likely that USE_GRID_SPACE_DIAGNOSTIC_AXES broke when I went from FMS1 to FMS2. Again, is this something I should care about? Do I go back to FMS1 or proceed with Andrew's fix?

 

[kshedstrom@alaska_edu]

Thanks for the reminder, Andrew! When I started this thread, I completely misunderstood what the flag referred to. I thought it was something to do with a vertical coordinate for diagnostics - I shouldn't need a separate such coordinate if I run in z* and want z-like output.

So anyway, I think I must have once had this on, because I have an example of cross-section outputs for one of my first Arctic runs. I had a Bering Strait and a number of other straits too. Now I can't get FMS to output such a thing in the native pseudo lon/lat 1-D horizontal coordinates because they are non-monotonic across the Arctic. This flag is exactly what I need for my Bering Strait issues.

 

[vivek]

Hi Kate and Andrew,

I am working NEP region and added USE_GRID_SPACE_DIAGNOSTIC_AXES as True, but I didn't see any changes in output. I need to save the output in the native grid.
The following options are added in the MOM_input file
! === module MOM_diag_mediator ===
USE_GRID_SPACE_DIAGNOSTIC_AXES = True
DIAG_COORD_DEF_Z = "FILE:vgrid_75_2m.nc,dz"