Wrap MPAS-A longitudes to [0, 2pi) range

[gdicker1]

What is the feature/what would you like to discuss?

While testing MPAS real-data initial conditions I proposed to add in #1029, F2000dev or F2000climo runs at 480km would fail while FADIAB runs would succeed. The cesm.log* files for failed runs would include many lines like imp_sol: Time step 1.1250000000000E+01 failed to converge ..., the amount of time per timestep would drastically increase, and runs would eventually terminate due to a CRITICAL ERROR: NaN detected in 'w' field. message from MPAS-A.

After a fair bit of trial and error, I think this comes down to some part of CAM expecting longitudes to be in the $[0,2\pi)$ range. This is not expected nor required by MPAS-A, and the MPAS-A *.grid.nc files may have longitudes ranging from $[0,2\pi]$ or $[-\pi, \pi]$ (or possibly even arbitrary radian values/ranges).

This is easily fixed by adding a few lines to put longitudes in the correct range. I propose to add these within cam_mpas_read_static subroutine in the cam_mpas_subdriver.F90 file. Since this will affect all longitude values, this change could affect regression tests.

Is there anyone in particular you want to be part of this conversation?

No response

Will this change (regression test) answers?

Yes

Will you be implementing this enhancement yourself?

Yes

[gdicker1]

Closed by merge of #1029