+Add segment%dZtot

  Add the new element dZtot to the OBC_segment_type to hold the total vertical
extent of the water column, and use thickness_to_dz in update_OBC_segment_data
to convert the layer thicknesses to the vertical layer extents used to set
dZtot.  This change leads to the cancellation of 6 unit conversion factors.
All answers are bitwise identical in Boussinesq mode, but they will change
and become less dependent on the Boussinesq reference density in some
Boussinesq cases with certain types of open boundary condition.

src/core/MOM_open_boundary.F90

@@ -14,6 +14,7 @@ module MOM_open_boundary
 use MOM_file_parser,          only : get_param, log_version, param_file_type, log_param
 use MOM_grid,                 only : ocean_grid_type, hor_index_type
 use MOM_dyn_horgrid,          only : dyn_horgrid_type
+use MOM_interface_heights,    only : thickness_to_dz
 use MOM_io,                   only : slasher, field_size, SINGLE_FILE
 use MOM_io,                   only : vardesc, query_vardesc, var_desc
 use MOM_restart,              only : register_restart_field, register_restart_pair
@@ -189,6 +190,7 @@ module MOM_open_boundary
   real, allocatable :: Cg(:,:)  !< The external gravity wave speed [L T-1 ~> m s-1]
                                 !! at OBC-points.
   real, allocatable :: Htot(:,:)  !< The total column thickness [H ~> m or kg m-2] at OBC-points.
+  real, allocatable :: dZtot(:,:) !< The total column vertical extent [Z ~> m] at OBC-points.
   real, allocatable :: h(:,:,:)   !< The cell thickness [H ~> m or kg m-2] at OBC-points.
   real, allocatable :: normal_vel(:,:,:)      !< The layer velocity normal to the OB
                                               !! segment [L T-1 ~> m s-1].
@@ -352,7 +354,7 @@ module MOM_open_boundary
   real, allocatable :: tres_y(:,:,:,:)   !< Array storage of tracer reservoirs for restarts, in unscaled units [conc]
   logical :: debug                       !< If true, write verbose checksums for debugging purposes.
   real :: silly_h  !< A silly value of thickness outside of the domain that can be used to test
-                   !! the independence of the OBCs to this external data [H ~> m or kg m-2].
+                   !! the independence of the OBCs to this external data [Z ~> m].
   real :: silly_u  !< A silly value of velocity outside of the domain that can be used to test
                    !! the independence of the OBCs to this external data [L T-1 ~> m s-1].
   logical :: ramp = .false.                 !< If True, ramp from zero to the external values for SSH.
@@ -3580,6 +3582,7 @@ subroutine allocate_OBC_segment_data(OBC, segment)
     ! If these are just Flather, change update_OBC_segment_data accordingly
     allocate(segment%Cg(IsdB:IedB,jsd:jed), source=0.0)
     allocate(segment%Htot(IsdB:IedB,jsd:jed), source=0.0)
+    allocate(segment%dZtot(IsdB:IedB,jsd:jed), source=0.0)
     allocate(segment%h(IsdB:IedB,jsd:jed,OBC%ke), source=0.0)
     allocate(segment%SSH(IsdB:IedB,jsd:jed), source=0.0)
     if (segment%radiation) &
@@ -3615,6 +3618,7 @@ subroutine allocate_OBC_segment_data(OBC, segment)
     ! If these are just Flather, change update_OBC_segment_data accordingly
     allocate(segment%Cg(isd:ied,JsdB:JedB), source=0.0)
     allocate(segment%Htot(isd:ied,JsdB:JedB), source=0.0)
+    allocate(segment%dZtot(isd:ied,JsdB:JedB), source=0.0)
     allocate(segment%h(isd:ied,JsdB:JedB,OBC%ke), source=0.0)
     allocate(segment%SSH(isd:ied,JsdB:JedB), source=0.0)
     if (segment%radiation) &
@@ -3656,6 +3660,7 @@ subroutine deallocate_OBC_segment_data(segment)
 
   if (allocated(segment%Cg)) deallocate(segment%Cg)
   if (allocated(segment%Htot)) deallocate(segment%Htot)
+  if (allocated(segment%dZtot)) deallocate(segment%dZtot)
   if (allocated(segment%h)) deallocate(segment%h)
   if (allocated(segment%SSH)) deallocate(segment%SSH)
   if (allocated(segment%rx_norm_rad)) deallocate(segment%rx_norm_rad)
@@ -3738,7 +3743,7 @@ subroutine open_boundary_test_extern_h(G, GV, OBC, h)
 
   if (.not. associated(OBC)) return
 
-  silly_h = GV%Z_to_H*OBC%silly_h
+  silly_h = GV%Z_to_H * OBC%silly_h
 
   do n = 1, OBC%number_of_segments
     do k = 1, GV%ke
@@ -3789,6 +3794,7 @@ subroutine update_OBC_segment_data(G, GV, US, OBC, tv, h, Time)
   integer :: ni_buf, nj_buf  ! Number of filled values in tmp_buffer
   integer :: is_obc, ie_obc, js_obc, je_obc  ! segment indices within local domain
   integer :: ishift, jshift  ! offsets for staggered locations
+  real, dimension(SZI_(G),SZJ_(G),SZK_(GV))  :: dz ! Distance between the interfaces around a layer [Z ~> m]
   real, dimension(:,:,:), allocatable, target :: tmp_buffer ! A buffer for input data [various units]
   real, dimension(:), allocatable :: h_stack  ! Thicknesses at corner points [H ~> m or kg m-2]
   integer :: is_obc2, js_obc2
@@ -3822,6 +3828,11 @@ subroutine update_OBC_segment_data(G, GV, US, OBC, tv, h, Time)
     h_neglect = GV%kg_m2_to_H * 1.0e-30 ; h_neglect_edge = GV%kg_m2_to_H * 1.0e-10
   endif
 
+  if (OBC%number_of_segments >= 1) then
+    call thickness_to_dz(h, tv, dz, G, GV, US)
+    call pass_var(dz, G%Domain)
+  endif
+
   do n = 1, OBC%number_of_segments
     segment => OBC%segment(n)
 
@@ -3854,23 +3865,27 @@ subroutine update_OBC_segment_data(G, GV, US, OBC, tv, h, Time)
       I=segment%HI%IsdB
       do j=segment%HI%jsd,segment%HI%jed
         segment%Htot(I,j) = 0.0
+        segment%dZtot(I,j) = 0.0
         do k=1,GV%ke
           segment%h(I,j,k) = h(i+ishift,j,k)
           segment%Htot(I,j) = segment%Htot(I,j) + segment%h(I,j,k)
+          segment%dZtot(I,j) = segment%dZtot(I,j) + dz(i+ishift,j,k)
         enddo
-        segment%Cg(I,j) = sqrt(GV%g_prime(1)*segment%Htot(I,j)*GV%H_to_Z)
+        segment%Cg(I,j) = sqrt(GV%g_prime(1) * segment%dZtot(I,j))
       enddo
     else! (segment%direction == OBC_DIRECTION_N .or. segment%direction == OBC_DIRECTION_S)
       allocate(normal_trans_bt(segment%HI%isd:segment%HI%ied,segment%HI%JsdB:segment%HI%JedB), source=0.0)
       if (segment%direction == OBC_DIRECTION_S) jshift=1
       J=segment%HI%JsdB
       do i=segment%HI%isd,segment%HI%ied
         segment%Htot(i,J) = 0.0
+        segment%dZtot(i,J) = 0.0
         do k=1,GV%ke
           segment%h(i,J,k) = h(i,j+jshift,k)
           segment%Htot(i,J) = segment%Htot(i,J) + segment%h(i,J,k)
+          segment%dZtot(i,J) = segment%dZtot(i,J) + dz(i,j+jshift,k)
         enddo
-        segment%Cg(i,J) = sqrt(GV%g_prime(1)*segment%Htot(i,J)*GV%H_to_Z)
+        segment%Cg(i,J) = sqrt(GV%g_prime(1) * segment%dZtot(i,J))
       enddo
     endif
 
@@ -5623,8 +5638,8 @@ subroutine adjustSegmentEtaToFitBathymetry(G, GV, US, segment,fld)
     ! The normal slope at the boundary is zero by a
     ! previous call to open_boundary_impose_normal_slope
     do k=nz+1,1,-1
-      if (-eta(i,j,k) > segment%Htot(i,j)*GV%H_to_Z + hTolerance) then
-        eta(i,j,k) = -segment%Htot(i,j)*GV%H_to_Z
+      if (-eta(i,j,k) > segment%dZtot(i,j) + hTolerance) then
+        eta(i,j,k) = -segment%dZtot(i,j)
         contractions = contractions + 1
       endif
     enddo
@@ -5642,10 +5657,10 @@ subroutine adjustSegmentEtaToFitBathymetry(G, GV, US, segment,fld)
 
     !   The whole column is dilated to accommodate deeper topography than
     ! the bathymetry would indicate.
-    if (-eta(i,j,nz+1) < (segment%Htot(i,j) * GV%H_to_Z) - hTolerance) then
+    if (-eta(i,j,nz+1) < segment%dZtot(i,j) - hTolerance) then
       dilations = dilations + 1
       ! expand bottom-most cell only
-      eta(i,j,nz+1) = -(segment%Htot(i,j) * GV%H_to_Z)
+      eta(i,j,nz+1) = -segment%dZtot(i,j)
       segment%field(fld)%dz_src(i,j,nz)= eta(i,j,nz)-eta(i,j,nz+1)
       ! if (eta(i,j,1) <= eta(i,j,nz+1)) then
       !   do k=1,nz ; segment%field(fld)%dz_src(i,j,k) = (eta(i,j,1) + G%bathyT(i,j)) / real(nz) ; enddo