Add ISOWGT and ISOVAR to topo files

[cacraigucar]

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

The ne30pg3_ne30pg3_mg17 topo file has this variable added to it. Other resolutions need to have this variable added to them. When those files exist, then the temporary fix in gw_drag.F90 can be removed.

When topo files are ready:
remove line:
if (.not. found) rdg_isowgt(:,:) = 0._r8

replace with:
if (.not. found) call endrun(sub//': ERROR: ISOWGT not found on topo file')

The same thing needs to be done for ISOVAR

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

@PeterHjortLauritzen - I am assigning you as Julio indicated you might be the one creating these new topo files. Whichever SE brings in those new files can also revert this line of code back
@JulioTBacmeister

Will this change (regression test) answers?

Yes

Will you be implementing this enhancement yourself?

Any CAM SE can do this