Merge branch 'atmosphere/gwdo_check_fix' into develop (PR #652)

This merge corrects the atmosphere_model's GWDO check to avoid incorrectly
halting the model when running a regional simulation entirely over water.

Originally, the GWDO check ensured that the GWDO fields were valid by checking
to see if the 'var2d' field was not all zero. For global simulations, an
all-zero 'var2d' field (with 'config_gwdo_scheme' not set to "off") most likely
meant that the user did not interpolate the GWDO fields.

However, regional MPAS simulations that were entirely over water would make
'var2d' and other GWDO fields all zero, which would incorrectly trigger this
error.

Now, the check on 'var2d' will only stop the model if not all grid cells are
water (based on the 'ivgtyp' field).

* atmosphere/gwdo_check_fix:
  Fix GWDO check on all water regional simulations

Author: mgduda

src/core_atmosphere/physics/mpas_atmphys_control.F

@@ -448,6 +448,9 @@ subroutine physics_compatibility_check(dminfo, blockList, streamManager, ierr)
  real (kind=RKIND) :: maxvar2d_local, maxvar2d_global
  real (kind=RKIND), dimension(:), pointer :: var2d
  integer, pointer :: nCellsSolve
+ integer, pointer :: iswater_lu
+ integer, pointer, dimension(:) :: ivgtyp
+ integer :: all_water, iall_water
  character (len=StrKIND), pointer :: gwdo_scheme
  type (block_type), pointer :: block
  type (mpas_pool_type), pointer :: meshPool
@@ -473,7 +476,22 @@ subroutine physics_compatibility_check(dminfo, blockList, streamManager, ierr)
 
      call mpas_dmpar_max_real(dminfo, maxvar2d_local, maxvar2d_global)
 
-     if (maxvar2d_global <= 0.0_RKIND) then
+     !
+     ! The GWDO check below can fail on regional simulations that are completely above
+     ! water. So, check to see if the simulation is completely above water and do not
+     ! throw the error if it is.
+     !
+     call mpas_pool_get_array(sfc_inputPool, 'iswater', iswater_lu)
+     call mpas_pool_get_array(sfc_inputPool, 'ivgtyp', ivgtyp)
+     if (all(ivgtyp(1:nCellsSolve) == iswater_lu)) then
+         all_water = 1 ! All water
+     else
+         all_water = 0 ! Land present
+     end if
+
+     call mpas_dmpar_min_int(dminfo, all_water, iall_water)
+
+     if (maxvar2d_global <= 0.0_RKIND .and. iall_water /= 1) then
          call mpas_log_write('*******************************************************************************', &
                              messageType=MPAS_LOG_ERR)
          call mpas_log_write('The GWDO scheme requires valid var2d, con, oa{1,2,3,4}, and ol{1,2,3,4} fields,', &