budget_total_tracer Function

   pure function budget_total_tracer(ms, it, mask, areaT) result(total)
      !! Total tracer content: Σ over masked interior of `hTr·areaT·weight`
      !! over k.  `hTr` is thickness-weighted, so this is ∫(tracer·volume),
      !! the conserved quantity.  Public only for the unit-test suite.
      type(multilayer_state_t), intent(in) :: ms
      integer, intent(in) :: it
      type(diag_mask_t), intent(in) :: mask
      real(wp), intent(in) :: areaT(:, :)
      real(wp) :: total
      integer :: i, j, k, nx, ny, nz
      real(wp) :: w_dA, col_sum
      total = 0.0_wp
      if (it <= 0) return
      if (.not. allocated(ms%tracers)) return
      if (it > size(ms%tracers)) return
      if (.not. allocated(ms%tracers(it)%hTr)) return
      nx = min(mask%nx, size(ms%tracers(it)%hTr, 1))
      ny = min(mask%ny, size(ms%tracers(it)%hTr, 2))
      nz = ms%nz_ml
      do j = 1, ny
         do i = 1, nx
            w_dA = mask%weight(i, j)*areaT(i, j)
            if (w_dA <= 0.0_wp) cycle
            col_sum = 0.0_wp
            do k = 1, nz
               col_sum = col_sum + ms%tracers(it)%hTr(i, j, k)
            end do
            total = total + w_dA*col_sum
         end do
      end do
   end function budget_total_tracer