ice_grid: do call 'gridbox_verts' for rectangular grids

[phil-blain]

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  base suite is bfb with CICE6.4.0, as expected:

349 measured results of 349 total results
349 of 349 tests PASSED
0 of 349 tests PENDING
0 of 349 tests MISSING data
0 of 349 tests FAILED

I also set up a case on a rectangular grid (gbox80) and compiled with -init=snan,arrays and verified that the code does not crash as it did before (see "Problems in ice_grid.F90" in #599 (comment)).

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At the end of subroutine ice_grid::gridbox_corners, the arrays
'lont_bounds' and 'lonu_bounds', which contain the longitude of the
corners of each grid cell on the T and U grids, are converted to to the
[0, 360] range.

In the case of rectangular grids ('grid_type = rectangular'), at the
point where 'gridbox_corners' is called in 'init_grid2', 'lont_bounds'
is not initialized, causing the code to abort if compiling with NaN
initialization. This is due to the fact that 'gridbox_verts', which
initializes 'lont_bounds' and 'latt_bounds', is not called in
'rectgrid', whereas it is called in 'popgrid[_nc]'.

Do call 'gridbox_verts' in 'rectgrid', so that 'lont_bounds' and
'latt_bounds' are correctly initalized in that case also.

Note that these calls are also missing in 'latlongrid' and 'cpomgrid',
but since these two subroutines are not used in standalone
configuration, let's not bother for now.

[phil-blain]

Maybe @dabail10 you would like to comment on the fact that these are also missing in latlongrid ? I can update that subroutine also if you wish.

Or, we could refactor a little bit more, and have gridbox_verts be called in init_grid2, instead of by each individual grid reading routine (thinking about it, that would be cleaner). But I don't know if it's mandatory for gridbox_verts to be called before the call to ice_HaloExtrapolate... If it does not matter then it would be safe to move the call to gridbox_verts to init_grid2, I would think.

[dabail10]

Not sure what to say here. This subroutine latlongrid was created for the atmosphere grids and prescribed ice mode. I thought we were reading in all the information instead of computing it. However, since dynamics is off in this configuration, a lot of the B-grid velocity information is not needed. We have actually moved away from using latlongrid now. We talked about removing it, but I think some groups still use it?

Maybe @dabail10 you would like to comment on the fact that these are also missing in latlongrid ? I can update that subroutine also if you wish.

Or, we could refactor a little bit more, and have gridbox_verts be called in init_grid2, instead of by each individual grid reading routine (thinking about it, that would be cleaner). But I don't know if it's mandatory for gridbox_verts to be called before the call to ice_HaloExtrapolate... If it does not matter then it would be safe to move the call to gridbox_verts to init_grid2, I would think.

[phil-blain]

OK, thanks. I pinged you because it's in between ifdef CESMCOUPLED. If the latlongrid subroutine is not used or in the process of being removed, we can just let it be, I would say.

[phil-blain]

I would have preferred that someone comment on my suggestion to move the call to gridbox_verts to init_grid2 before merging, I think this would have been cleaner... but anyway let's keep what we have for now. Thanks!