(*)Consolidate conversion of 4 salt tendency diags

  Collected the conversion factors for the 4 salt tendency diagnostics
diabatic_salt_tendency, diabatic_salt_tendency_2d, boundary_forcing_salt_tendency
and boundary_forcing_heat_tendency_2d out of the calculation of the diagnostics
before they are posted and into the conversion argument in their
register_diag_field calls.  This change simplifies the code where the
diagnostics are calculated, but although all expressions are mathematically
equivalent, there is a change in the order of arithmetic with which these 4
diagnostics are calculated, so answers will change at roundoff, although this is
unlikely to be detected if the diagnostics are being written as 32 bit floats.
All model solutions are bitwise identical.

src/parameterizations/vertical/MOM_diabatic_driver.F90

@@ -2724,7 +2724,6 @@ subroutine diagnose_diabatic_diff_tendency(tv, h, temp_old, saln_old, dt, G, GV,
   real, dimension(SZI_(G),SZJ_(G),SZK_(GV)) :: work_3d ! A 3-d work array for diagnostics [various]
   real, dimension(SZI_(G),SZJ_(G))          :: work_2d ! A 2-d work array for diagnostics [various]
   real :: Idt  ! The inverse of the timestep [T-1 ~> s-1]
-  real :: ppt2mks  ! Conversion factor from S to kg/kg [S-1 ~> ppt-1].
   integer :: i, j, k, is, ie, js, je, nz
   logical :: do_saln_tend   ! Calculate salinity-based tendency diagnostics
 
@@ -2774,9 +2773,8 @@ subroutine diagnose_diabatic_diff_tendency(tv, h, temp_old, saln_old, dt, G, GV,
 
     ! salt tendency
     if (CS%id_diabatic_diff_salt_tend > 0 .or. CS%id_diabatic_diff_salt_tend_2d > 0) then
-      ppt2mks = US%S_to_ppt*0.001
       do k=1,nz ; do j=js,je ; do i=is,ie
-        work_3d(i,j,k) = h(i,j,k)*GV%H_to_RZ * ppt2mks * work_3d(i,j,k)
+        work_3d(i,j,k) = h(i,j,k) * work_3d(i,j,k)
       enddo ; enddo ; enddo
       if (CS%id_diabatic_diff_salt_tend > 0) then
         call post_data(CS%id_diabatic_diff_salt_tend, work_3d, CS%diag, alt_h=h)
@@ -2819,7 +2817,6 @@ subroutine diagnose_boundary_forcing_tendency(tv, h, temp_old, saln_old, h_old,
   real, dimension(SZI_(G),SZJ_(G),SZK_(GV)) :: work_3d ! A 3-d work array for diagnostics [various]
   real, dimension(SZI_(G),SZJ_(G))          :: work_2d ! A 2-d work array for diagnostics [various]
   real :: Idt  ! The inverse of the timestep [T-1 ~> s-1]
-  real :: ppt2mks  ! Conversion factor from S to kg/kg [S-1 ~> ppt-1].
   integer :: i, j, k, is, ie, js, je, nz
 
   is  = G%isc ; ie = G%iec ; js = G%jsc ; je = G%jec ; nz = GV%ke
@@ -2870,9 +2867,8 @@ subroutine diagnose_boundary_forcing_tendency(tv, h, temp_old, saln_old, h_old,
 
   ! salt tendency
   if (CS%id_boundary_forcing_salt_tend > 0 .or. CS%id_boundary_forcing_salt_tend_2d > 0) then
-    ppt2mks = US%S_to_ppt*0.001
     do k=1,nz ; do j=js,je ; do i=is,ie
-      work_3d(i,j,k) = GV%H_to_RZ * ppt2mks * Idt * (h(i,j,k) * tv%S(i,j,k) - h_old(i,j,k) * saln_old(i,j,k))
+      work_3d(i,j,k) = Idt * (h(i,j,k) * tv%S(i,j,k) - h_old(i,j,k) * saln_old(i,j,k))
     enddo ; enddo ; enddo
     if (CS%id_boundary_forcing_salt_tend > 0) then
       call post_data(CS%id_boundary_forcing_salt_tend, work_3d, CS%diag, alt_h=h_old)
@@ -3372,7 +3368,8 @@ subroutine diabatic_driver_init(Time, G, GV, US, param_file, useALEalgorithm, di
     CS%id_diabatic_diff_salt_tend = register_diag_field('ocean_model',                   &
         'diabatic_salt_tendency', diag%axesTL, Time,                                     &
         'Diabatic diffusion of salt tendency',                                           &
-        'kg m-2 s-1', conversion=US%RZ_T_to_kg_m2s, cmor_field_name='osaltdiff', &
+        'kg m-2 s-1', conversion=US%S_to_ppt*0.001*GV%H_to_RZ*US%RZ_T_to_kg_m2s, &
+        cmor_field_name='osaltdiff', &
         cmor_standard_name='tendency_of_sea_water_salinity_expressed_as_salt_content_'// &
                            'due_to_parameterized_dianeutral_mixing',                     &
         cmor_long_name='Tendency of sea water salinity expressed as salt content '//     &
@@ -3399,7 +3396,8 @@ subroutine diabatic_driver_init(Time, G, GV, US, param_file, useALEalgorithm, di
     CS%id_diabatic_diff_salt_tend_2d = register_diag_field('ocean_model',                &
         'diabatic_salt_tendency_2d', diag%axesT1, Time,                                  &
         'Depth integrated diabatic diffusion salt tendency',                             &
-        'kg m-2 s-1', conversion=US%RZ_T_to_kg_m2s, cmor_field_name='osaltdiff_2d',              &
+        'kg m-2 s-1', conversion=US%S_to_ppt*0.001*GV%H_to_RZ*US%RZ_T_to_kg_m2s, &
+        cmor_field_name='osaltdiff_2d', &
         cmor_standard_name='tendency_of_sea_water_salinity_expressed_as_salt_content_'// &
                            'due_to_parameterized_dianeutral_mixing_depth_integrated',    &
         cmor_long_name='Tendency of sea water salinity expressed as salt content '//     &
@@ -3446,7 +3444,8 @@ subroutine diabatic_driver_init(Time, G, GV, US, param_file, useALEalgorithm, di
 
     CS%id_boundary_forcing_salt_tend = register_diag_field('ocean_model',&
         'boundary_forcing_salt_tendency', diag%axesTL, Time,             &
-        'Boundary forcing salt tendency', 'kg m-2 s-1', conversion=US%RZ_T_to_kg_m2s, &
+        'Boundary forcing salt tendency', &
+        'kg m-2 s-1', conversion=US%S_to_ppt*0.001*GV%H_to_RZ*US%RZ_T_to_kg_m2s, &
         v_extensive = .true.)
     if (CS%id_boundary_forcing_salt_tend > 0) then
       CS%boundary_forcing_tendency_diag = .true.
@@ -3465,7 +3464,7 @@ subroutine diabatic_driver_init(Time, G, GV, US, param_file, useALEalgorithm, di
     CS%id_boundary_forcing_salt_tend_2d = register_diag_field('ocean_model',&
         'boundary_forcing_salt_tendency_2d', diag%axesT1, Time,             &
         'Depth integrated boundary forcing of ocean salt', &
-        'kg m-2 s-1', conversion=US%RZ_T_to_kg_m2s)
+        'kg m-2 s-1', conversion=US%S_to_ppt*0.001*GV%H_to_RZ*US%RZ_T_to_kg_m2s)
     if (CS%id_boundary_forcing_salt_tend_2d > 0) then
       CS%boundary_forcing_tendency_diag = .true.
     endif