ocean_varmix_init Subroutine

   subroutine ocean_varmix_init(this, grid, nz_ml)
      !! Allocate the static grid terms, the per-step diagnostics, and the
      !! KhTh/KhTr base face fields.  Always allocates (configure runs after
      !! init); the static `f2_dx2_*` / `beta_dx2_*` / `l2_*` are filled by
      !! `build_static` once the metrics + f_centre are known.  Setup uses
      !! plain host allocation (no `do concurrent` before enter_data).
      class(ocean_varmix_t), intent(inout) :: this
      type(hgrid_t), intent(in) :: grid
      integer, intent(in), optional :: nz_ml
      integer :: nx, ny, nz

      nx = grid%nx_total
      ny = grid%ny_total
      nz = 1
      if (present(nz_ml)) nz = nz_ml
      if (nz < 1) nz = 1
      if (nz > NZ_STACK_MAX) then
         error stop "ocean_varmix_init: nz_ml exceeds NZ_STACK_MAX "// &
            "(raise NZ_STACK_MAX in rdb_constants)"
      end if
      this%nx_total = nx
      this%ny_total = ny
      this%nz_ml = nz

      allocate (this%f2_dx2_u(nx + 1, ny), source=0.0_wp)
      allocate (this%f2_dx2_v(nx, ny + 1), source=0.0_wp)
      allocate (this%beta_dx2_u(nx + 1, ny), source=0.0_wp)
      allocate (this%beta_dx2_v(nx, ny + 1), source=0.0_wp)
      allocate (this%l2_u(nx + 1, ny), source=0.0_wp)
      allocate (this%l2_v(nx, ny + 1), source=0.0_wp)
      allocate (this%res_fn_u(nx + 1, ny), source=0.0_wp)
      allocate (this%res_fn_v(nx, ny + 1), source=0.0_wp)
      allocate (this%sn_u(nx + 1, ny), source=0.0_wp)
      allocate (this%sn_v(nx, ny + 1), source=0.0_wp)
      allocate (this%khth_u(nx + 1, ny), source=0.0_wp)
      allocate (this%khth_v(nx, ny + 1), source=0.0_wp)
      allocate (this%khtr_u(nx + 1, ny), source=0.0_wp)
      allocate (this%khtr_v(nx, ny + 1), source=0.0_wp)
      this%is_init = .true.
   end subroutine ocean_varmix_init