      SUBROUTINE tl_uv3dmix4 (ng, tile)
!
!svn $Id$
!************************************************** Hernan G. Arango ***
!  Copyright (c) 2002-2020 The ROMS/TOMS Group       Andrew M. Moore   !
!    Licensed under a MIT/X style license                              !
!    See License_ROMS.txt                                              !
!***********************************************************************
!                                                                      !
!  This subroutine computes tangent linear biharmonic mixing of        !
!  momentum,  rotated along geopotentials,  from the horizontal        !
!  divergence of the stress tensor.  A  transverse  isotropy is        !
!  assumed  so the  stress  tensor is split into  vertical  and        !
!  horizontal subtensors.                                              !
!                                                                      !
!  Reference:                                                          !
!                                                                      !
!      Wajsowicz, R.C, 1993: A consistent formulation of the           !
!         anisotropic stress tensor for use in models of the           !
!         large-scale ocean circulation, JCP, 105, 333-338.            !
!                                                                      !
!      Sadourny, R. and K. Maynard, 1997: Formulations of              !
!         lateral diffusion in geophysical fluid dynamics              !
!         models, In Numerical Methods of Atmospheric and              !
!         Oceanic Modelling. Lin, Laprise, and Ritchie,                !
!         Eds., NRC Research Press, 547-556.                           !
!                                                                      !
!      Griffies, S.M. and R.W. Hallberg, 2000: Biharmonic              !
!         friction with a Smagorinsky-like viscosity for               !
!         use in large-scale eddy-permitting ocean models,             !
!         Monthly Weather Rev., 128, 8, 2935-2946.                     !
!                                                                      !
!***********************************************************************
!
      USE mod_param
      USE mod_coupling
#ifdef DIAGNOSTICS_UV
!!    USE mod_diags
#endif
      USE mod_grid
      USE mod_mixing
      USE mod_ocean
      USE mod_stepping
!
!  Imported variable declarations.
!
      integer, intent(in) :: ng, tile
!
!  Local variable declarations.
!
#include "tile.h"
!
#ifdef PROFILE
      CALL wclock_on (ng, iTLM, 33, __LINE__, __FILE__)
#endif
      CALL tl_uv3dmix4_tile (ng, tile,                                  &
     &                       LBi, UBi, LBj, UBj,                        &
     &                       IminS, ImaxS, JminS, JmaxS,                &
     &                       nrhs(ng), nnew(ng),                        &
#ifdef MASKING
     &                       GRID(ng) % pmask,                          &
     &                       GRID(ng) % rmask,                          &
     &                       GRID(ng) % umask,                          &
     &                       GRID(ng) % vmask,                          &
#endif
     &                       GRID(ng) % om_p,                           &
     &                       GRID(ng) % om_r,                           &
     &                       GRID(ng) % om_u,                           &
     &                       GRID(ng) % om_v,                           &
     &                       GRID(ng) % on_p,                           &
     &                       GRID(ng) % on_r,                           &
     &                       GRID(ng) % on_u,                           &
     &                       GRID(ng) % on_v,                           &
     &                       GRID(ng) % pm,                             &
     &                       GRID(ng) % pn,                             &
     &                       GRID(ng) % Hz,                             &
     &                       GRID(ng) % tl_Hz,                          &
     &                       GRID(ng) % z_r,                            &
     &                       GRID(ng) % tl_z_r,                         &
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
     &                       MIXING(ng) % Uvis3d_r,                     &
     &                       MIXING(ng) % Vvis3d_r,                     &
     &                       MIXING(ng) % tl_Uvis3d_r,                  &
     &                       MIXING(ng) % tl_Vvis3d_r,                  &
# else
     &                       MIXING(ng) % visc3d_r,                     &
     &                       MIXING(ng) % tl_visc3d_r,                  &
# endif
#else
     &                       MIXING(ng) % visc4_p,                      &
     &                       MIXING(ng) % visc4_r,                      &
#endif
#ifdef DIAGNOSTICS_UV
!!   &                       DIAGS(ng) % DiaRUfrc,                      &
!!   &                       DIAGS(ng) % DiaRVfrc,                      &
!!   &                       DIAGS(ng) % DiaU3wrk,                      &
!!   &                       DIAGS(ng) % DiaV3wrk,                      &
#endif
     &                       OCEAN(ng) % u,                             &
     &                       OCEAN(ng) % v,                             &
     &                       OCEAN(ng) % tl_u,                          &
     &                       OCEAN(ng) % tl_v,                          &
     &                       COUPLING(ng) % tl_rufrc,                   &
     &                       COUPLING(ng) % tl_rvfrc)
#ifdef PROFILE
      CALL wclock_off (ng, iTLM, 33, __LINE__, __FILE__)
#endif

      RETURN
      END SUBROUTINE tl_uv3dmix4
!
!***********************************************************************
      SUBROUTINE tl_uv3dmix4_tile (ng, tile,                            &
     &                             LBi, UBi, LBj, UBj,                  &
     &                             IminS, ImaxS, JminS, JmaxS,          &
     &                             nrhs, nnew,                          &
#ifdef MASKING
     &                             pmask, rmask, umask, vmask,          &
#endif
     &                             om_p, om_r, om_u, om_v,              &
     &                             on_p, on_r, on_u, on_v,              &
     &                             pm, pn,                              &
     &                             Hz, tl_Hz,                           &
     &                             z_r, tl_z_r,                         &
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
     &                             Uvis3d_r, Vvis3d_r,                  &
     &                             tl_Uvis3d_r, tl_Vvis3d_r,            &
# else
     &                             visc3d_r, tl_visc3d_r,               &
# endif
#else
     &                             visc4_p, visc4_r,                    &
#endif
#ifdef DIAGNOSTICS_UV
!!   &                             DiaRUfrc, DiaRVfrc,                  &
!!   &                             DiaU3wrk, DiaV3wrk,                  &
#endif
     &                             u, v,                                &
     &                             tl_u, tl_v,                          &
     &                             tl_rufrc, tl_rvfrc)
!***********************************************************************
!
      USE mod_param
      USE mod_ncparam
      USE mod_scalars
!
!  Imported variable declarations.
!
      integer, intent(in) :: ng, tile
      integer, intent(in) :: LBi, UBi, LBj, UBj
      integer, intent(in) :: IminS, ImaxS, JminS, JmaxS
      integer, intent(in) :: nrhs, nnew

#ifdef ASSUMED_SHAPE
# ifdef MASKING
      real(r8), intent(in) :: pmask(LBi:,LBj:)
      real(r8), intent(in) :: rmask(LBi:,LBj:)
      real(r8), intent(in) :: umask(LBi:,LBj:)
      real(r8), intent(in) :: vmask(LBi:,LBj:)
# endif
      real(r8), intent(in) :: om_p(LBi:,LBj:)
      real(r8), intent(in) :: om_r(LBi:,LBj:)
      real(r8), intent(in) :: om_u(LBi:,LBj:)
      real(r8), intent(in) :: om_v(LBi:,LBj:)
      real(r8), intent(in) :: on_p(LBi:,LBj:)
      real(r8), intent(in) :: on_r(LBi:,LBj:)
      real(r8), intent(in) :: on_u(LBi:,LBj:)
      real(r8), intent(in) :: on_v(LBi:,LBj:)
      real(r8), intent(in) :: pm(LBi:,LBj:)
      real(r8), intent(in) :: pn(LBi:,LBj:)
      real(r8), intent(in) :: Hz(LBi:,LBj:,:)
      real(r8), intent(in) :: tl_Hz(LBi:,LBj:,:)
      real(r8), intent(in) :: z_r(LBi:,LBj:,:)
      real(r8), intent(in) :: tl_z_r(LBi:,LBj:,:)
# ifdef VISC_3DCOEF
#  ifdef UV_U3ADV_SPLIT
      real(r8), intent(in) :: Uvis3d_r(LBi:,LBj:,:)
      real(r8), intent(in) :: Vvis3d_r(LBi:,LBj:,:)
#  else
      real(r8), intent(in) :: visc3d_r(LBi:,LBj:,:)
#  endif
# else
      real(r8), intent(in) :: visc4_p(LBi:,LBj:)
      real(r8), intent(in) :: visc4_r(LBi:,LBj:)
# endif
      real(r8), intent(in) :: u(LBi:,LBj:,:,:)
      real(r8), intent(in) :: v(LBi:,LBj:,:,:)

# ifdef DIAGNOSTICS_UV
!!    real(r8), intent(inout) :: DiaRUfrc(LBi:,LBj:,:,:)
!!    real(r8), intent(inout) :: DiaRVfrc(LBi:,LBj:,:,:)
!!    real(r8), intent(inout) :: DiaU3wrk(LBi:,LBj:,:,:)
!!    real(r8), intent(inout) :: DiaV3wrk(LBi:,LBj:,:,:)
# endif
# ifdef VISC_3DCOEF
#  ifdef UV_U3ADV_SPLIT
      real(r8), intent(inout) :: tl_Uvis3d_r(LBi:,LBj:,:)
      real(r8), intent(inout) :: tl_Vvis3d_r(LBi:,LBj:,:)
#  else
      real(r8), intent(inout) :: tl_visc3d_r(LBi:,LBj:,:)
#  endif
# endif
      real(r8), intent(inout) :: tl_rufrc(LBi:,LBj:)
      real(r8), intent(inout) :: tl_rvfrc(LBi:,LBj:)
      real(r8), intent(inout) :: tl_u(LBi:,LBj:,:,:)
      real(r8), intent(inout) :: tl_v(LBi:,LBj:,:,:)
#else
# ifdef MASKING
      real(r8), intent(in) :: pmask(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: rmask(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: umask(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: vmask(LBi:UBi,LBj:UBj)
# endif
      real(r8), intent(in) :: om_p(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: om_r(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: om_u(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: om_v(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: on_p(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: on_r(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: on_u(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: on_v(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: pm(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: pn(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: Hz(LBi:UBi,LBj:UBj,N(ng))
      real(r8), intent(in) :: tl_Hz(LBi:UBi,LBj:UBj,N(ng))
      real(r8), intent(in) :: z_r(LBi:UBi,LBj:UBj,N(ng))
      real(r8), intent(in) :: tl_z_r(LBi:UBi,LBj:UBj,N(ng))
# ifdef VISC_3DCOEF
#  ifdef UV_U3ADV_SPLIT
      real(r8), intent(in) :: Uvis3d_r(LBi:UBi,LBj:UBj,N(ng))
      real(r8), intent(in) :: Vvis3d_r(LBi:UBi,LBj:UBj,N(ng))
#  else
      real(r8), intent(in) :: visc3d_r(LBi:UBi,LBj:UBj,N(ng))
#  endif
# else
      real(r8), intent(in) :: visc4_p(LBi:UBi,LBj:UBj)
      real(r8), intent(in) :: visc4_r(LBi:UBi,LBj:UBj)
# endif
      real(r8), intent(in) :: u(LBi:UBi,LBj:UBj,N(ng),2)
      real(r8), intent(in) :: v(LBi:UBi,LBj:UBj,N(ng),2)

# ifdef DIAGNOSTICS_UV
!!    real(r8), intent(inout) :: DiaRUfrc(LBi:UBi,LBj:UBj,3,NDM2d-1)
!!    real(r8), intent(inout) :: DiaRVfrc(LBi:UBi,LBj:UBj,3,NDM2d-1)
!!    real(r8), intent(inout) :: DiaU3wrk(LBi:UBi,LBj:UBj,N(ng),NDM3d)
!!    real(r8), intent(inout) :: DiaV3wrk(LBi:UBi,LBj:UBj,N(ng),NDM3d)
# endif
# ifdef VISC_3DCOEF
#  ifdef UV_U3ADV_SPLIT
      real(r8), intent(inout) :: tl_Uvis3d_r(LBi:UBi,LBj:UBj,N(ng))
      real(r8), intent(inout) :: tl_Vvis3d_r(LBi:UBi,LBj:UBj,N(ng))
#  else
      real(r8), intent(inout) :: tl_visc3d_r(LBi:UBi,LBj:UBj,N(ng))
#  endif
# endif
      real(r8), intent(inout) :: tl_rufrc(LBi:UBi,LBj:UBj)
      real(r8), intent(inout) :: tl_rvfrc(LBi:UBi,LBj:UBj)
      real(r8), intent(inout) :: tl_u(LBi:UBi,LBj:UBj,N(ng),2)
      real(r8), intent(inout) :: tl_v(LBi:UBi,LBj:UBj,N(ng),2)
#endif
!
!  Local variable declarations.
!
      integer :: i, j, k, k1, k2

      real(r8) :: cff, fac1, fac2, pm_p, pn_p
      real(r8) :: cff1, cff2, cff3, cff4
      real(r8) :: cff5, cff6, cff7, cff8
      real(r8) :: dmUdz, dnUdz, dmVdz, dnVdz
#ifdef VISC_3DCOEF
      real(r8) :: Uvis_p, Vvis_p, visc_p
      real(r8) :: tl_fac1, tl_fac2, tl_Uvis_p, tl_Vvis_p, tl_visc_p
#endif
      real(r8) :: tl_cff
      real(r8) :: tl_cff1, tl_cff2, tl_cff3, tl_cff4
      real(r8) :: tl_cff5, tl_cff6, tl_cff7, tl_cff8
      real(r8) :: tl_dmUdz, tl_dnUdz, tl_dmVdz, tl_dnVdz

      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,N(ng)) :: LapU
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,N(ng)) :: LapV

      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,N(ng)) :: tl_LapU
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,N(ng)) :: tl_LapV

      real(r8), dimension(IminS:ImaxS,JminS:JmaxS) :: UFe
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS) :: UFx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS) :: VFe
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS) :: VFx

      real(r8), dimension(IminS:ImaxS,JminS:JmaxS) :: tl_UFe
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS) :: tl_UFx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS) :: tl_VFe
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS) :: tl_VFx

      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: UFse
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: UFsx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: VFse
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: VFsx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dmUde
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dmVde
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dnUdx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dnVdx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dUdz
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dVdz
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dZde_p
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dZde_r
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dZdx_p
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: dZdx_r

      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_UFse
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_UFsx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_VFse
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_VFsx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dmUde
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dmVde
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dnUdx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dnVdx
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dUdz
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dVdz
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dZde_p
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dZde_r
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dZdx_p
      real(r8), dimension(IminS:ImaxS,JminS:JmaxS,2) :: tl_dZdx_r

#include "set_bounds.h"
!
!-----------------------------------------------------------------------
!  Compute horizontal biharmonic viscosity along geopotential
!  surfaces.  The biharmonic operator is computed by applying
!  the harmonic operator twice.
!-----------------------------------------------------------------------
!
!  Compute horizontal and vertical gradients.  Notice the recursive
!  blocking sequence. It is assumed here that the mixing coefficients
!  are the squared root of the biharmonic viscosity coefficient. For
!  momentum balance purposes, the thickness "Hz" appears only when
!  computing the second harmonic operator. The vertical placement of
!  the gradients is:
!
!    dZdx_r, dZde_r, dnUdx, dmVde(:,:,k1) k      rho-points
!    dZdx_r, dZde_r, dnUdx, dmVde(:,:,k2) k+1    rho-points
!    dZdx_p, dZde_p, dnVdx, dmUde(:,:,k1) k      psi-points
!    dZdx_p, dZde_p, dnVdx, dmUde(:,:,k2) k+1    psi-points
!                UFse, UFsx, dUdz(:,:,k1) k-1/2  WU-points
!                UFse, UFsx, dUdz(:,:,k2) k+1/2  WU-points
!                VFse, VFsx, dVdz(:,:,k1) k-1/2  WV-points
!                VFse, VFsx, dVdz(:,:,k2) k+1/2  WV-points
!
      k2=1
      K_LOOP1 : DO k=0,N(ng)
        k1=k2
        k2=3-k1
        IF (k.lt.N(ng)) THEN
!
!  Compute slopes (nondimensional) at RHO- and PSI-points.
!
          DO j=Jstrm2,Jendp2
            DO i=IstrUm2,Iendp2
              cff=0.5_r8*(pm(i-1,j)+pm(i,j))
#ifdef MASKING
              cff=cff*umask(i,j)
#endif
              UFx(i,j)=cff*(z_r(i  ,j,k+1)-                             &
     &                      z_r(i-1,j,k+1))
              tl_UFx(i,j)=cff*(tl_z_r(i  ,j,k+1)-                       &
     &                         tl_z_r(i-1,j,k+1))
            END DO
          END DO
          DO j=JstrVm2,Jendp2
            DO i=Istrm2,Iendp2
              cff=0.5_r8*(pn(i,j-1)+pn(i,j))
#ifdef MASKING
              cff=cff*vmask(i,j)
#endif
              VFe(i,j)=cff*(z_r(i,j  ,k+1)-                             &
     &                      z_r(i,j-1,k+1))
              tl_VFe(i,j)=cff*(tl_z_r(i,j  ,k+1)-                       &
     &                         tl_z_r(i,j-1,k+1))
            END DO
          END DO
!
          DO j=Jstrm1,Jendp2
            DO i=Istrm1,Iendp2
              dZdx_p(i,j,k2)=0.5_r8*(UFx(i,j-1)+                        &
     &                               UFx(i,j  ))
              tl_dZdx_p(i,j,k2)=0.5_r8*(tl_UFx(i,j-1)+                  &
     &                                  tl_UFx(i,j  ))
              dZde_p(i,j,k2)=0.5_r8*(VFe(i-1,j)+                        &
     &                               VFe(i  ,j))
              tl_dZde_p(i,j,k2)=0.5_r8*(tl_VFe(i-1,j)+                  &
     &                                  tl_VFe(i  ,j))
            END DO
          END DO
          DO j=JstrVm2,Jendp1
            DO i=IstrUm2,Iendp1
              dZdx_r(i,j,k2)=0.5_r8*(UFx(i  ,j)+                        &
     &                               UFx(i+1,j))
              tl_dZdx_r(i,j,k2)=0.5_r8*(tl_UFx(i  ,j)+                  &
     &                                  tl_UFx(i+1,j))
              dZde_r(i,j,k2)=0.5_r8*(VFe(i,j  )+                        &
     &                               VFe(i,j+1))
              tl_dZde_r(i,j,k2)=0.5_r8*(tl_VFe(i,j  )+                  &
     &                                  tl_VFe(i,j+1))
            END DO
          END DO
!
!  Compute momentum horizontal (1/m/s) and vertical (1/s) gradients.
!
          DO j=JstrVm2,Jendp1
            DO i=IstrUm2,Iendp1
              cff=0.5_r8*pm(i,j)
#ifdef MASKING
              cff=cff*rmask(i,j)
#endif
              dnUdx(i,j,k2)=cff*((pn(i  ,j)+pn(i+1,j))*                 &
     &                           u(i+1,j,k+1,nrhs)-                     &
     &                           (pn(i-1,j)+pn(i  ,j))*                 &
     &                           u(i  ,j,k+1,nrhs))
              tl_dnUdx(i,j,k2)=cff*((pn(i  ,j)+pn(i+1,j))*              &
     &                              tl_u(i+1,j,k+1,nrhs)-               &
     &                              (pn(i-1,j)+pn(i  ,j))*              &
     &                              tl_u(i  ,j,k+1,nrhs))
            END DO
          END DO

          DO j=Jstrm1,Jendp2
            DO i=Istrm1,Iendp2
              cff=0.125_r8*(pn(i-1,j  )+pn(i,j  )+                      &
     &                      pn(i-1,j-1)+pn(i,j-1))
#ifdef MASKING
              cff=cff*pmask(i,j)
#endif
              dmUde(i,j,k2)=cff*((pm(i-1,j  )+pm(i,j  ))*               &
     &                           u(i,j  ,k+1,nrhs)-                     &
     &                           (pm(i-1,j-1)+pm(i,j-1))*               &
     &                           u(i,j-1,k+1,nrhs))
              tl_dmUde(i,j,k2)=cff*((pm(i-1,j  )+pm(i,j  ))*            &
     &                              tl_u(i,j  ,k+1,nrhs)-               &
     &                              (pm(i-1,j-1)+pm(i,j-1))*            &
     &                              tl_u(i,j-1,k+1,nrhs))
            END DO
          END DO

          DO j=Jstrm1,Jendp2
            DO i=Istrm1,Iendp2
              cff=0.125_r8*(pm(i-1,j  )+pm(i,j  )+                      &
     &                      pm(i-1,j-1)+pm(i,j-1))
#ifdef MASKING
              cff=cff*pmask(i,j)
#endif
              dnVdx(i,j,k2)=cff*((pn(i  ,j-1)+pn(i  ,j))*               &
     &                           v(i  ,j,k+1,nrhs)-                     &
     &                           (pn(i-1,j-1)+pn(i-1,j))*               &
     &                           v(i-1,j,k+1,nrhs))
              tl_dnVdx(i,j,k2)=cff*((pn(i  ,j-1)+pn(i  ,j))*            &
     &                              tl_v(i  ,j,k+1,nrhs)-               &
     &                              (pn(i-1,j-1)+pn(i-1,j))*            &
     &                              tl_v(i-1,j,k+1,nrhs))
            END DO
          END DO

          DO j=JstrVm2,Jendp1
            DO i=IstrUm2,Iendp1
              cff=0.5_r8*pn(i,j)
#ifdef MASKING
              cff=cff*rmask(i,j)
#endif
              dmVde(i,j,k2)=cff*((pm(i,j  )+pm(i,j+1))*                 &
     &                           v(i,j+1,k+1,nrhs)-                     &
     &                           (pm(i,j-1)+pm(i,j  ))*                 &
     &                           v(i,j  ,k+1,nrhs))
              tl_dmVde(i,j,k2)=cff*((pm(i,j  )+pm(i,j+1))*              &
     &                              tl_v(i,j+1,k+1,nrhs)-               &
     &                              (pm(i,j-1)+pm(i,j  ))*              &
     &                              tl_v(i,j  ,k+1,nrhs))
            END DO
          END DO
        END IF

        IF ((k.eq.0).or.(k.eq.N(ng))) THEN
          DO j=Jstrm2,Jendp2
            DO i=IstrUm2,Iendp2
              dUdz(i,j,k2)=0.0_r8
              tl_dUdz(i,j,k2)=0.0_r8
            END DO
          END DO
          DO j=JstrVm2,Jendp2
            DO i=Istrm2,Iendp2
              dVdz(i,j,k2)=0.0_r8
              tl_dVdz(i,j,k2)=0.0_r8
            END DO
          END DO

          DO j=Jstrm1,Jendp1
            DO i=IstrUm1,Iendp1
              UFsx(i,j,k2)=0.0_r8
              tl_UFsx(i,j,k2)=0.0_r8
              UFse(i,j,k2)=0.0_r8
              tl_UFse(i,j,k2)=0.0_r8
            END DO
          END DO
          DO j=JstrVm1,Jendp1
            DO i=Istrm1,Iendp1
              VFsx(i,j,k2)=0.0_r8
              tl_VFsx(i,j,k2)=0.0_r8
              VFse(i,j,k2)=0.0_r8
              tl_VFse(i,j,k2)=0.0_r8
            END DO
          END DO
        ELSE
          DO j=Jstrm2,Jendp2
            DO i=IstrUm2,Iendp2
              cff=1.0_r8/(0.5_r8*(z_r(i-1,j,k+1)-                       &
     &                            z_r(i-1,j,k  )+                       &
     &                            z_r(i  ,j,k+1)-                       &
     &                            z_r(i  ,j,k  )))
              tl_cff=-cff*cff*(0.5_r8*(tl_z_r(i-1,j,k+1)-               &
     &                                 tl_z_r(i-1,j,k  )+               &
     &                                 tl_z_r(i  ,j,k+1)-               &
     &                                 tl_z_r(i  ,j,k  )))
              dUdz(i,j,k2)=cff*(u(i,j,k+1,nrhs)-                        &
     &                          u(i,j,k  ,nrhs))
              tl_dUdz(i,j,k2)=tl_cff*(u(i,j,k+1,nrhs)-                  &
     &                                u(i,j,k  ,nrhs))+                 &
     &                        cff*(tl_u(i,j,k+1,nrhs)-                  &
     &                             tl_u(i,j,k  ,nrhs))
            END DO
          END DO

          DO j=JstrVm2,Jendp2
            DO i=Istrm2,Iendp2
              cff=1.0_r8/(0.5_r8*(z_r(i,j-1,k+1)-                       &
     &                            z_r(i,j-1,k  )+                       &
     &                            z_r(i,j  ,k+1)-                       &
     &                            z_r(i,j  ,k  )))
              tl_cff=-cff*cff*(0.5_r8*(tl_z_r(i,j-1,k+1)-               &
     &                                 tl_z_r(i,j-1,k  )+               &
     &                                 tl_z_r(i,j  ,k+1)-               &
     &                                 tl_z_r(i,j  ,k  )))
              dVdz(i,j,k2)=cff*(v(i,j,k+1,nrhs)-                        &
     &                          v(i,j,k  ,nrhs))
              tl_dVdz(i,j,k2)=tl_cff*(v(i,j,k+1,nrhs)-                  &
     &                                v(i,j,k  ,nrhs))+                 &
     &                        cff*(tl_v(i,j,k+1,nrhs)-                  &
     &                             tl_v(i,j,k  ,nrhs))
            END DO
          END DO
        END IF
!
!  Compute components of the rotated viscous flux (m^4 s-^3/2) along
!  geopotential surfaces in the XI- and ETA-directions.
!
        IF (k.gt.0) THEN
          DO j=JstrVm2,Jendp1
            DO i=IstrUm2,Iendp1
              cff1=MIN(dZdx_r(i,j,k1),0.0_r8)
              cff2=MAX(dZdx_r(i,j,k1),0.0_r8)
              cff3=MIN(dZde_r(i,j,k1),0.0_r8)
              cff4=MAX(dZde_r(i,j,k1),0.0_r8)
              tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i,j,k1)))*            &
     &                tl_dZdx_r(i,j,k1)
              tl_cff2=(0.5_r8+SIGN(0.5_r8, dZdx_r(i,j,k1)))*            &
     &                tl_dZdx_r(i,j,k1)
              tl_cff3=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j,k1)))*            &
     &                tl_dZde_r(i,j,k1)
              tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j,k1)))*            &
     &                tl_dZde_r(i,j,k1)
              cff=on_r(i,j)*(dnUdx(i,j,k1)-                             &
     &                       0.5_r8*pn(i,j)*                            &
     &                       (cff1*(dUdz(i  ,j,k1)+                     &
     &                              dUdz(i+1,j,k2))+                    &
     &                        cff2*(dUdz(i  ,j,k2)+                     &
     &                              dUdz(i+1,j,k1))))-                  &
     &            om_r(i,j)*(dmVde(i,j,k1)-                             &
     &                       0.5_r8*pm(i,j)*                            &
     &                       (cff3*(dVdz(i,j  ,k1)+                     &
     &                              dVdz(i,j+1,k2))+                    &
     &                        cff4*(dVdz(i,j  ,k2)+                     &
     &                              dVdz(i,j+1,k1))))
              tl_cff=on_r(i,j)*(tl_dnUdx(i,j,k1)-                       &
     &                          0.5_r8*pn(i,j)*                         &
     &                          (tl_cff1*(dUdz(i  ,j,k1)+               &
     &                                    dUdz(i+1,j,k2))+              &
     &                           cff1*(tl_dUdz(i  ,j,k1)+               &
     &                                 tl_dUdz(i+1,j,k2))+              &
     &                           tl_cff2*(dUdz(i  ,j,k2)+               &
     &                                    dUdz(i+1,j,k1))+              &
     &                           cff2*(tl_dUdz(i  ,j,k2)+               &
     &                                 tl_dUdz(i+1,j,k1))))-            &
     &               om_r(i,j)*(tl_dmVde(i,j,k1)-                       &
     &                          0.5_r8*pm(i,j)*                         &
     &                          (tl_cff3*(dVdz(i,j  ,k1)+               &
     &                                    dVdz(i,j+1,k2))+              &
     &                           cff3*(tl_dVdz(i,j  ,k1)+               &
     &                                 tl_dVdz(i,j+1,k2))+              &
     &                           tl_cff4*(dVdz(i,j  ,k2)+               &
     &                                    dVdz(i,j+1,k1))+              &
     &                           cff4*(tl_dVdz(i,j  ,k2)+               &
     &                                 tl_dVdz(i,j+1,k1))))
#ifdef MASKING
              cff=cff*rmask(i,j)
              tl_cff=tl_cff*rmask(i,j)
#endif
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
              UFx(i,j)=on_r(i,j)*on_r(i,j)*Uvis3d_r(i,j,k)*cff
              tl_UFx(i,j)=on_r(i,j)*on_r(i,j)*                          &
     &                    (tl_Uvis3d_r(i,j,k)*cff+                      &
     &                     Uvis3d_r(i,j,k)*tl_cff)
              VFe(i,j)=om_r(i,j)*om_r(i,j)*Vvis3d_r(i,j,k)*cff
              tl_VFe(i,j)=om_r(i,j)*om_r(i,j)*                          &
     &                    (tl_Vvis3d_r(i,j,k)*cff+                      &
     &                     Vvis3d_r(i,j,k)*tl_cff)
# else
              UFx(i,j)=on_r(i,j)*on_r(i,j)*visc3d_r(i,j,k)*cff
              tl_UFx(i,j)=on_r(i,j)*on_r(i,j)*                          &
     &                    (tl_visc3d_r(i,j,k)*cff+                      &
     &                     visc3d_r(i,j,k)*tl_cff)
              VFe(i,j)=om_r(i,j)*om_r(i,j)*visc3d_r(i,j,k)*cff
              tl_VFe(i,j)=om_r(i,j)*om_r(i,j)*                          &
     &                    (tl_visc3d_r(i,j,k)*cff+                      &
     &                     visc3d_r(i,j,k)*tl_cff)
# endif
#else
              UFx(i,j)=on_r(i,j)*on_r(i,j)*visc4_r(i,j)*cff
              tl_UFx(i,j)=on_r(i,j)*on_r(i,j)*visc4_r(i,j)*tl_cff
              VFe(i,j)=om_r(i,j)*om_r(i,j)*visc4_r(i,j)*cff
              tl_VFe(i,j)=om_r(i,j)*om_r(i,j)*visc4_r(i,j)*tl_cff
#endif
            END DO
          END DO

          DO j=Jstrm1,Jendp2
            DO i=Istrm1,Iendp2
              pm_p=0.25_r8*(pm(i-1,j-1)+pm(i-1,j)+                      &
     &                      pm(i  ,j-1)+pm(i  ,j))
              pn_p=0.25_r8*(pn(i-1,j-1)+pn(i-1,j)+                      &
     &                      pn(i  ,j-1)+pn(i  ,j))
              cff1=MIN(dZdx_p(i,j,k1),0.0_r8)
              cff2=MAX(dZdx_p(i,j,k1),0.0_r8)
              cff3=MIN(dZde_p(i,j,k1),0.0_r8)
              cff4=MAX(dZde_p(i,j,k1),0.0_r8)
              tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i,j,k1)))*            &
     &                tl_dZdx_p(i,j,k1)
              tl_cff2=(0.5_r8+SIGN(0.5_r8, dZdx_p(i,j,k1)))*            &
     &                tl_dZdx_p(i,j,k1)
              tl_cff3=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j,k1)))*            &
     &                tl_dZde_p(i,j,k1)
              tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j,k1)))*            &
     &                tl_dZde_p(i,j,k1)
              cff=on_p(i,j)*(dnVdx(i,j,k1)-                             &
     &                       0.5_r8*pn_p*                               &
     &                       (cff1*(dVdz(i-1,j,k1)+                     &
     &                              dVdz(i  ,j,k2))+                    &
     &                        cff2*(dVdz(i-1,j,k2)+                     &
     &                              dVdz(i  ,j,k1))))+                  &
     &            om_p(i,j)*(dmUde(i,j,k1)-                             &
     &                       0.5_r8*pm_p*                               &
     &                       (cff3*(dUdz(i,j-1,k1)+                     &
     &                              dUdz(i,j  ,k2))+                    &
     &                        cff4*(dUdz(i,j-1,k2)+                     &
     &                              dUdz(i,j  ,k1))))
              tl_cff=on_p(i,j)*(tl_dnVdx(i,j,k1)-                       &
     &                          0.5_r8*pn_p*                            &
     &                          (tl_cff1*(dVdz(i-1,j,k1)+               &
     &                                    dVdz(i  ,j,k2))+              &
     &                           cff1*(tl_dVdz(i-1,j,k1)+               &
     &                                 tl_dVdz(i  ,j,k2))+              &
     &                           tl_cff2*(dVdz(i-1,j,k2)+               &
     &                                    dVdz(i  ,j,k1))+              &
     &                           cff2*(tl_dVdz(i-1,j,k2)+               &
     &                                 tl_dVdz(i  ,j,k1))))+            &
     &               om_p(i,j)*(tl_dmUde(i,j,k1)-                       &
     &                          0.5_r8*pm_p*                            &
     &                          (tl_cff3*(dUdz(i,j-1,k1)+               &
     &                                    dUdz(i,j  ,k2))+              &
     &                           cff3*(tl_dUdz(i,j-1,k1)+               &
     &                                 tl_dUdz(i,j  ,k2))+              &
     &                           tl_cff4*(dUdz(i,j-1,k2)+               &
     &                                    dUdz(i,j  ,k1))+              &
     &                           cff4*(tl_dUdz(i,j-1,k2)+               &
     &                                 tl_dUdz(i,j  ,k1))))
#ifdef MASKING
              cff=cff*pmask(i,j)
              tl_cff=tl_cff*pmask(i,j)
#endif
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
              Uvis_p=0.25_r8*                                           &
     &               (Uvis3d_r(i-1,j-1,k)+Uvis3d_r(i-1,j,k)+            &
     &                Uvis3d_r(i  ,j-1,k)+Uvis3d_r(i  ,j,k))
              tl_Uvis_p=0.25_r8*                                        &
     &                  (tl_Uvis3d_r(i-1,j-1,k)+tl_Uvis3d_r(i-1,j,k)+   &
     &                   tl_Uvis3d_r(i  ,j-1,k)+tl_Uvis3d_r(i  ,j,k))
              Vvis_p=0.25_r8*                                           &
     &               (Vvis3d_r(i-1,j-1,k)+Vvis3d_r(i-1,j,k)+            &
     &                Vvis3d_r(i  ,j-1,k)+Vvis3d_r(i  ,j,k))
              tl_Vvis_p=0.25_r8*                                        &
     &                  (tl_Vvis3d_r(i-1,j-1,k)+tl_Vvis3d_r(i-1,j,k)+   &
     &                   tl_Vvis3d_r(i  ,j-1,k)+tl_Vvis3d_r(i  ,j,k))
              UFe(i,j)=om_p(i,j)*om_p(i,j)*Uvis_p*cff
              tl_UFe(i,j)=om_p(i,j)*om_p(i,j)*                          &
     &                    (tl_Uvis_p*cff+Uvis_p*tl_cff)
              VFx(i,j)=on_p(i,j)*on_p(i,j)*Vvis_p*cff
              tl_VFx(i,j)=on_p(i,j)*on_p(i,j)*                          &
     &                    (tl_Vvis_p*cff+Vvis_p*tl_cff)
# else
              visc_p=0.25_r8*                                           &
     &               (visc3d_r(i-1,j-1,k)+visc3d_r(i-1,j,k)+            &
     &                visc3d_r(i  ,j-1,k)+visc3d_r(i  ,j,k))
              tl_visc_p=0.25_r8*                                        &
     &                  (tl_visc3d_r(i-1,j-1,k)+tl_visc3d_r(i-1,j,k)+   &
     &                   tl_visc3d_r(i  ,j-1,k)+tl_visc3d_r(i  ,j,k))
              UFe(i,j)=om_p(i,j)*om_p(i,j)*visc_p*cff
              tl_UFe(i,j)=om_p(i,j)*om_p(i,j)*                          &
     &                    (tl_visc_p*cff+visc_p*tl_cff)
              VFx(i,j)=on_p(i,j)*on_p(i,j)*visc_p*cff
              tl_VFx(i,j)=on_p(i,j)*on_p(i,j)*                          &
     &                    (tl_visc_p*cff+visc_p*tl_cff)
# endif
#else
              UFe(i,j)=om_p(i,j)*om_p(i,j)*visc4_p(i,j)*cff
              tl_UFe(i,j)=om_p(i,j)*om_p(i,j)*visc4_p(i,j)*tl_cff
              VFx(i,j)=on_p(i,j)*on_p(i,j)*visc4_p(i,j)*cff
              tl_VFx(i,j)=on_p(i,j)*on_p(i,j)*visc4_p(i,j)*tl_cff
#endif
            END DO
          END DO
!
!  Compute vertical flux (m^2 s^-3/2) due to sloping terrain-following
!  surfaces.
!
          IF (k.lt.N(ng)) THEN
            DO j=Jstrm1,Jendp1
              DO i=IstrUm1,Iendp1
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
                cff=0.125_r8*                                           &
     &              (Uvis3d_r(i-1,j,k  )+Uvis3d_r(i,j,k  )+             &
     &               Uvis3d_r(i-1,j,k+1)+Uvis3d_r(i,j,k+1))
                tl_cff=0.125_r8*                                        &
     &                 (tl_Uvis3d_r(i-1,j,k  )+tl_Uvis3d_r(i,j,k  )+    &
     &                  tl_Uvis3d_r(i-1,j,k+1)+tl_Uvis3d_r(i,j,k+1))
# else
                cff=0.125_r8*                                           &
     &              (visc3d_r(i-1,j,k  )+visc3d_r(i,j,k  )+             &
     &               visc3d_r(i-1,j,k+1)+visc3d_r(i,j,k+1))
                tl_cff=0.125_r8*                                        &
     &                 (tl_visc3d_r(i-1,j,k  )+tl_visc3d_r(i,j,k  )+    &
     &                  tl_visc3d_r(i-1,j,k+1)+tl_visc3d_r(i,j,k+1))
# endif
                fac1=cff*on_u(i,j)
                tl_fac1=tl_cff*on_u(i,j)
                fac2=cff*om_u(i,j)
                tl_fac2=tl_cff*om_u(i,j)
#else
                cff=0.25_r8*(visc4_r(i-1,j)+visc4_r(i,j))
                fac1=cff*on_u(i,j)
                fac2=cff*om_u(i,j)
#endif
                cff=0.5_r8*(pn(i-1,j)+pn(i,j))
                dnUdz=cff*dUdz(i,j,k2)
                tl_dnUdz=cff*tl_dUdz(i,j,k2)
                dnVdz=cff*0.25_r8*(dVdz(i-1,j+1,k2)+                    &
     &                             dVdz(i  ,j+1,k2)+                    &
     &                             dVdz(i-1,j  ,k2)+                    &
     &                             dVdz(i  ,j  ,k2))
                tl_dnVdz=cff*0.25_r8*(tl_dVdz(i-1,j+1,k2)+              &
     &                                tl_dVdz(i  ,j+1,k2)+              &
     &                                tl_dVdz(i-1,j  ,k2)+              &
     &                                tl_dVdz(i  ,j  ,k2))
                cff=0.5_r8*(pm(i-1,j)+pm(i,j))
                dmUdz=cff*dUdz(i,j,k2)
                tl_dmUdz=cff*tl_dUdz(i,j,k2)
                dmVdz=cff*0.25_r8*(dVdz(i-1,j+1,k2)+                    &
     &                             dVdz(i  ,j+1,k2)+                    &
     &                             dVdz(i-1,j  ,k2)+                    &
     &                             dVdz(i  ,j  ,k2))
                tl_dmVdz=cff*0.25_r8*(tl_dVdz(i-1,j+1,k2)+              &
     &                                tl_dVdz(i  ,j+1,k2)+              &
     &                                tl_dVdz(i-1,j  ,k2)+              &
     &                                tl_dVdz(i  ,j  ,k2))

                cff1=MIN(dZdx_r(i-1,j,k1),0.0_r8)
                cff2=MIN(dZdx_r(i  ,j,k2),0.0_r8)
                cff3=MAX(dZdx_r(i-1,j,k2),0.0_r8)
                cff4=MAX(dZdx_r(i  ,j,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i-1,j,k1)))*        &
     &                  tl_dZdx_r(i-1,j,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i  ,j,k2)))*        &
     &                  tl_dZdx_r(i  ,j,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZdx_r(i-1,j,k2)))*        &
     &                  tl_dZdx_r(i-1,j,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZdx_r(i  ,j,k1)))*        &
     &                  tl_dZdx_r(i  ,j,k1)
                UFsx(i,j,k2)=fac1*                                      &
     &                       (cff1*(cff1*dnUdz-dnUdx(i-1,j,k1))+        &
     &                        cff2*(cff2*dnUdz-dnUdx(i  ,j,k2))+        &
     &                        cff3*(cff3*dnUdz-dnUdx(i-1,j,k2))+        &
     &                        cff4*(cff4*dnUdz-dnUdx(i  ,j,k1)))
                tl_UFsx(i,j,k2)=fac1*                                   &
     &                          (tl_cff1*(cff1*dnUdz-dnUdx(i-1,j,k1))+  &
     &                           tl_cff2*(cff2*dnUdz-dnUdx(i  ,j,k2))+  &
     &                           tl_cff3*(cff3*dnUdz-dnUdx(i-1,j,k2))+  &
     &                           tl_cff4*(cff4*dnUdz-dnUdx(i  ,j,k1))+  &
     &                           cff1*(tl_cff1*dnUdz+cff1*tl_dnUdz-     &
     &                                 tl_dnUdx(i-1,j,k1))+             &
     &                           cff2*(tl_cff2*dnUdz+cff2*tl_dnUdz-     &
     &                                 tl_dnUdx(i  ,j,k2))+             &
     &                           cff3*(tl_cff3*dnUdz+cff3*tl_dnUdz-     &
     &                                 tl_dnUdx(i-1,j,k2))+             &
     &                           cff4*(tl_cff4*dnUdz+cff4*tl_dnUdz-     &
     &                                 tl_dnUdx(i  ,j,k1)))
#ifdef VISC_3DCOEF
                tl_UFsx(i,j,k2)=tl_UFsx(i,j,k2)+                        &
     &                          tl_fac1*                                &
     &                          (cff1*(cff1*dnUdz-dnUdx(i-1,j,k1))+     &
     &                           cff2*(cff2*dnUdz-dnUdx(i  ,j,k2))+     &
     &                           cff3*(cff3*dnUdz-dnUdx(i-1,j,k2))+     &
     &                           cff4*(cff4*dnUdz-dnUdx(i  ,j,k1)))
#endif

                cff1=MIN(dZde_p(i,j  ,k1),0.0_r8)
                cff2=MIN(dZde_p(i,j+1,k2),0.0_r8)
                cff3=MAX(dZde_p(i,j  ,k2),0.0_r8)
                cff4=MAX(dZde_p(i,j+1,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j  ,k1)))*        &
     &                  tl_dZde_p(i,j  ,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j+1,k2)))*        &
     &                  tl_dZde_p(i,j+1,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j  ,k2)))*        &
     &                  tl_dZde_p(i,j  ,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j+1,k1)))*        &
     &                  tl_dZde_p(i,j+1,k1)
                UFse(i,j,k2)=fac2*                                      &
     &                       (cff1*(cff1*dmUdz-dmUde(i,j  ,k1))+        &
     &                        cff2*(cff2*dmUdz-dmUde(i,j+1,k2))+        &
     &                        cff3*(cff3*dmUdz-dmUde(i,j  ,k2))+        &
     &                        cff4*(cff4*dmUdz-dmUde(i,j+1,k1)))
                tl_UFse(i,j,k2)=fac2*                                   &
     &                          (tl_cff1*(cff1*dmUdz-dmUde(i,j  ,k1))+  &
     &                           tl_cff2*(cff2*dmUdz-dmUde(i,j+1,k2))+  &
     &                           tl_cff3*(cff3*dmUdz-dmUde(i,j  ,k2))+  &
     &                           tl_cff4*(cff4*dmUdz-dmUde(i,j+1,k1))+  &
     &                           cff1*(tl_cff1*dmUdz+cff1*tl_dmUdz-     &
     &                                 tl_dmUde(i,j  ,k1))+             &
     &                           cff2*(tl_cff2*dmUdz+cff2*tl_dmUdz-     &
     &                                 tl_dmUde(i,j+1,k2))+             &
     &                           cff3*(tl_cff3*dmUdz+cff3*tl_dmUdz-     &
     &                                 tl_dmUde(i,j  ,k2))+             &
     &                           cff4*(tl_cff4*dmUdz+cff4*tl_dmUdz-     &
     &                                 tl_dmUde(i,j+1,k1)))
#ifdef VISC_3DCOEF
                tl_UFse(i,j,k2)=tl_UFse(i,j,k2)+                        &
     &                          tl_fac2*                                &
     &                          (cff1*(cff1*dmUdz-dmUde(i,j  ,k1))+     &
     &                           cff2*(cff2*dmUdz-dmUde(i,j+1,k2))+     &
     &                           cff3*(cff3*dmUdz-dmUde(i,j  ,k2))+     &
     &                           cff4*(cff4*dmUdz-dmUde(i,j+1,k1)))
#endif

                cff1=MIN(dZde_p(i,j  ,k1),0.0_r8)
                cff2=MIN(dZde_p(i,j+1,k2),0.0_r8)
                cff3=MAX(dZde_p(i,j  ,k2),0.0_r8)
                cff4=MAX(dZde_p(i,j+1,k1),0.0_r8)
                cff5=MIN(dZdx_p(i,j  ,k1),0.0_r8)
                cff6=MIN(dZdx_p(i,j+1,k2),0.0_r8)
                cff7=MAX(dZdx_p(i,j  ,k2),0.0_r8)
                cff8=MAX(dZdx_p(i,j+1,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j  ,k1)))*        &
     &                  tl_dZde_p(i,j  ,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j+1,k2)))*        &
     &                  tl_dZde_p(i,j+1,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j  ,k2)))*        &
     &                  tl_dZde_p(i,j  ,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j+1,k1)))*        &
     &                  tl_dZde_p(i,j+1,k1)
                tl_cff5=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i,j  ,k1)))*        &
     &                  tl_dZdx_p(i,j  ,k1)
                tl_cff6=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i,j+1,k2)))*        &
     &                  tl_dZdx_p(i,j+1,k2)
                tl_cff7=(0.5_r8+SIGN(0.5_r8, dZdx_p(i,j  ,k2)))*        &
     &                  tl_dZdx_p(i,j  ,k2)
                tl_cff8=(0.5_r8+SIGN(0.5_r8, dZdx_p(i,j+1,k1)))*        &
     &                  tl_dZdx_p(i,j+1,k1)
                UFsx(i,j,k2)=UFsx(i,j,k2)+                              &
     &                       fac1*                                      &
     &                       (cff1*(cff5*dnVdz-dnVdx(i,j  ,k1))+        &
     &                        cff2*(cff6*dnVdz-dnVdx(i,j+1,k2))+        &
     &                        cff3*(cff7*dnVdz-dnVdx(i,j  ,k2))+        &
     &                        cff4*(cff8*dnVdz-dnVdx(i,j+1,k1)))
                tl_UFsx(i,j,k2)=tl_UFsx(i,j,k2)+                        &
     &                          fac1*                                   &
     &                          (tl_cff1*(cff5*dnVdz-dnVdx(i,j  ,k1))+  &
     &                           tl_cff2*(cff6*dnVdz-dnVdx(i,j+1,k2))+  &
     &                           tl_cff3*(cff7*dnVdz-dnVdx(i,j  ,k2))+  &
     &                           tl_cff4*(cff8*dnVdz-dnVdx(i,j+1,k1))+  &
     &                           cff1*(tl_cff5*dnVdz+cff5*tl_dnVdz-     &
     &                                 tl_dnVdx(i,j  ,k1))+             &
     &                           cff2*(tl_cff6*dnVdz+cff6*tl_dnVdz-     &
     &                                 tl_dnVdx(i,j+1,k2))+             &
     &                           cff3*(tl_cff7*dnVdz+cff7*tl_dnVdz-     &
     &                                 tl_dnVdx(i,j  ,k2))+             &
     &                           cff4*(tl_cff8*dnVdz+cff8*tl_dnVdz-     &
     &                                 tl_dnVdx(i,j+1,k1)))
#ifdef VISC_3DCOEF
                tl_UFsx(i,j,k2)=tl_UFsx(i,j,k2)+                        &
     &                          tl_fac1*                                &
     &                          (cff1*(cff5*dnVdz-dnVdx(i,j  ,k1))+     &
     &                           cff2*(cff6*dnVdz-dnVdx(i,j+1,k2))+     &
     &                           cff3*(cff7*dnVdz-dnVdx(i,j  ,k2))+     &
     &                           cff4*(cff8*dnVdz-dnVdx(i,j+1,k1)))
#endif

                cff1=MIN(dZdx_r(i-1,j,k1),0.0_r8)
                cff2=MIN(dZdx_r(i  ,j,k2),0.0_r8)
                cff3=MAX(dZdx_r(i-1,j,k2),0.0_r8)
                cff4=MAX(dZdx_r(i  ,j,k1),0.0_r8)
                cff5=MIN(dZde_r(i-1,j,k1),0.0_r8)
                cff6=MIN(dZde_r(i  ,j,k2),0.0_r8)
                cff7=MAX(dZde_r(i-1,j,k2),0.0_r8)
                cff8=MAX(dZde_r(i  ,j,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i-1,j,k1)))*        &
     &                  tl_dZdx_r(i-1,j,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i  ,j,k2)))*        &
     &                  tl_dZdx_r(i  ,j,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZdx_r(i-1,j,k2)))*        &
     &                  tl_dZdx_r(i-1,j,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZdx_r(i  ,j,k1)))*        &
     &                  tl_dZdx_r(i  ,j,k1)
                tl_cff5=(0.5_r8+SIGN(0.5_r8,-dZde_r(i-1,j,k1)))*        &
     &                  tl_dZde_r(i-1,j,k1)
                tl_cff6=(0.5_r8+SIGN(0.5_r8,-dZde_r(i  ,j,k2)))*        &
     &                  tl_dZde_r(i  ,j,k2)
                tl_cff7=(0.5_r8+SIGN(0.5_r8, dZde_r(i-1,j,k2)))*        &
     &                  tl_dZde_r(i-1,j,k2)
                tl_cff8=(0.5_r8+SIGN(0.5_r8, dZde_r(i  ,j,k1)))*        &
     &                  tl_dZde_r(i  ,j,k1)
                UFse(i,j,k2)=UFse(i,j,k2)-                              &
     &                       fac2*                                      &
     &                       (cff1*(cff5*dmVdz-dmVde(i-1,j,k1))+        &
     &                        cff2*(cff6*dmVdz-dmVde(i  ,j,k2))+        &
     &                        cff3*(cff7*dmVdz-dmVde(i-1,j,k2))+        &
     &                        cff4*(cff8*dmVdz-dmVde(i  ,j,k1)))
                tl_UFse(i,j,k2)=tl_UFse(i,j,k2)-                        &
     &                          fac2*                                   &
     &                          (tl_cff1*(cff5*dmVdz-dmVde(i-1,j,k1))+  &
     &                           tl_cff2*(cff6*dmVdz-dmVde(i  ,j,k2))+  &
     &                           tl_cff3*(cff7*dmVdz-dmVde(i-1,j,k2))+  &
     &                           tl_cff4*(cff8*dmVdz-dmVde(i  ,j,k1))+  &
     &                           cff1*(tl_cff5*dmVdz+cff5*tl_dmVdz-     &
     &                                 tl_dmVde(i-1,j,k1))+             &
     &                           cff2*(tl_cff6*dmVdz+cff6*tl_dmVdz-     &
     &                                 tl_dmVde(i  ,j,k2))+             &
     &                           cff3*(tl_cff7*dmVdz+cff7*tl_dmVdz-     &
     &                                 tl_dmVde(i-1,j,k2))+             &
     &                           cff4*(tl_cff8*dmVdz+cff8*tl_dmVdz-     &
     &                                 tl_dmVde(i  ,j,k1)))
#ifdef VISC_3DCOEF
                tl_UFse(i,j,k2)=tl_UFse(i,j,k2)-                        &
     &                          tl_fac2*                                &
     &                          (cff1*(cff5*dmVdz-dmVde(i-1,j,k1))+     &
     &                           cff2*(cff6*dmVdz-dmVde(i  ,j,k2))+     &
     &                           cff3*(cff7*dmVdz-dmVde(i-1,j,k2))+     &
     &                           cff4*(cff8*dmVdz-dmVde(i  ,j,k1)))
#endif
              END DO
            END DO
!
            DO j=JstrVm1,Jendp1
              DO i=Istrm1,Iendp1
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
                cff=0.125_r8*                                           &
     &              (Vvis3d_r(i,j-1,k  )+Vvis3d_r(i,j,k  )+             &
     &               Vvis3d_r(i,j-1,k+1)+Vvis3d_r(i,j,k+1))
                tl_cff=0.125_r8*                                        &
     &                 (tl_Vvis3d_r(i,j-1,k  )+tl_Vvis3d_r(i,j,k  )+    &
     &                  tl_Vvis3d_r(i,j-1,k+1)+tl_Vvis3d_r(i,j,k+1))
# else
                cff=0.125_r8*                                           &
     &              (visc3d_r(i,j-1,k  )+visc3d_r(i,j,k  )+             &
     &               visc3d_r(i,j-1,k+1)+visc3d_r(i,j,k+1))
                tl_cff=0.125_r8*                                        &
     &                 (tl_visc3d_r(i,j-1,k  )+tl_visc3d_r(i,j,k  )+    &
     &                  tl_visc3d_r(i,j-1,k+1)+tl_visc3d_r(i,j,k+1))
# endif
                fac1=cff*on_v(i,j)
                tl_fac1=tl_cff*on_v(i,j)
                fac2=cff*om_v(i,j)
                tl_fac2=tl_cff*om_v(i,j)
#else
                cff=0.25_r8*(visc4_r(i,j-1)+visc4_r(i,j))
                fac1=cff*on_v(i,j)
                fac2=cff*om_v(i,j)
#endif
                cff=0.5_r8*(pn(i,j-1)+pn(i,j))
                dnUdz=cff*0.25_r8*(dUdz(i  ,j  ,k2)+                    &
     &                             dUdz(i+1,j  ,k2)+                    &
     &                             dUdz(i  ,j-1,k2)+                    &
     &                             dUdz(i+1,j-1,k2))
                tl_dnUdz=cff*0.25_r8*(tl_dUdz(i  ,j  ,k2)+              &
     &                                tl_dUdz(i+1,j  ,k2)+              &
     &                                tl_dUdz(i  ,j-1,k2)+              &
     &                                tl_dUdz(i+1,j-1,k2))
                dnVdz=cff*dVdz(i,j,k2)
                tl_dnVdz=cff*tl_dVdz(i,j,k2)
                cff=0.5_r8*(pm(i,j-1)+pm(i,j))
                dmUdz=cff*0.25_r8*(dUdz(i  ,j  ,k2)+                    &
     &                             dUdz(i+1,j  ,k2)+                    &
     &                             dUdz(i  ,j-1,k2)+                    &
     &                             dUdz(i+1,j-1,k2))
                tl_dmUdz=cff*0.25_r8*(tl_dUdz(i  ,j  ,k2)+              &
     &                                tl_dUdz(i+1,j  ,k2)+              &
     &                                tl_dUdz(i  ,j-1,k2)+              &
     &                                tl_dUdz(i+1,j-1,k2))
                dmVdz=cff*dVdz(i,j,k2)
                tl_dmVdz=cff*tl_dVdz(i,j,k2)

                cff1=MIN(dZdx_p(i  ,j,k1),0.0_r8)
                cff2=MIN(dZdx_p(i+1,j,k2),0.0_r8)
                cff3=MAX(dZdx_p(i  ,j,k2),0.0_r8)
                cff4=MAX(dZdx_p(i+1,j,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i  ,j,k1)))*        &
     &                  tl_dZdx_p(i  ,j,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i+1,j,k2)))*        &
     &                  tl_dZdx_p(i+1,j,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZdx_p(i  ,j,k2)))*        &
     &                  tl_dZdx_p(i  ,j,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZdx_p(i+1,j,k1)))*        &
     &                  tl_dZdx_p(i+1,j,k1)
                VFsx(i,j,k2)=fac1*                                      &
     &                       (cff1*(cff1*dnVdz-dnVdx(i  ,j,k1))+        &
     &                        cff2*(cff2*dnVdz-dnVdx(i+1,j,k2))+        &
     &                        cff3*(cff3*dnVdz-dnVdx(i  ,j,k2))+        &
     &                        cff4*(cff4*dnVdz-dnVdx(i+1,j,k1)))
                tl_VFsx(i,j,k2)=fac1*                                   &
     &                          (tl_cff1*(cff1*dnVdz-dnVdx(i  ,j,k1))+  &
     &                           tl_cff2*(cff2*dnVdz-dnVdx(i+1,j,k2))+  &
     &                           tl_cff3*(cff3*dnVdz-dnVdx(i  ,j,k2))+  &
     &                           tl_cff4*(cff4*dnVdz-dnVdx(i+1,j,k1))+  &
     &                           cff1*(tl_cff1*dnVdz+cff1*tl_dnVdz-     &
     &                                 tl_dnVdx(i  ,j,k1))+             &
     &                           cff2*(tl_cff2*dnVdz+cff2*tl_dnVdz-     &
     &                                 tl_dnVdx(i+1,j,k2))+             &
     &                           cff3*(tl_cff3*dnVdz+cff3*tl_dnVdz-     &
     &                                 tl_dnVdx(i  ,j,k2))+             &
     &                           cff4*(tl_cff4*dnVdz+cff4*tl_dnVdz-     &
     &                                 tl_dnVdx(i+1,j,k1)))
#ifdef VISC_3DCOEF
                tl_VFsx(i,j,k2)=tl_VFsx(i,j,k2)+                        &
     &                          tl_fac1*                                &
     &                          (cff1*(cff1*dnVdz-dnVdx(i  ,j,k1))+     &
     &                           cff2*(cff2*dnVdz-dnVdx(i+1,j,k2))+     &
     &                           cff3*(cff3*dnVdz-dnVdx(i  ,j,k2))+     &
     &                           cff4*(cff4*dnVdz-dnVdx(i+1,j,k1)))
#endif

                cff1=MIN(dZde_r(i,j-1,k1),0.0_r8)
                cff2=MIN(dZde_r(i,j  ,k2),0.0_r8)
                cff3=MAX(dZde_r(i,j-1,k2),0.0_r8)
                cff4=MAX(dZde_r(i,j  ,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j-1,k1)))*        &
     &                  tl_dZde_r(i,j-1,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j  ,k2)))*        &
     &                  tl_dZde_r(i,j  ,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j-1,k2)))*        &
     &                  tl_dZde_r(i,j-1,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j  ,k1)))*        &
     &                  tl_dZde_r(i,j  ,k1)
                VFse(i,j,k2)=fac2*                                      &
     &                       (cff1*(cff1*dmVdz-dmVde(i,j-1,k1))+        &
     &                        cff2*(cff2*dmVdz-dmVde(i,j  ,k2))+        &
     &                        cff3*(cff3*dmVdz-dmVde(i,j-1,k2))+        &
     &                        cff4*(cff4*dmVdz-dmVde(i,j  ,k1)))
                tl_VFse(i,j,k2)=fac2*                                   &
     &                          (tl_cff1*(cff1*dmVdz-dmVde(i,j-1,k1))+  &
     &                           tl_cff2*(cff2*dmVdz-dmVde(i,j  ,k2))+  &
     &                           tl_cff3*(cff3*dmVdz-dmVde(i,j-1,k2))+  &
     &                           tl_cff4*(cff4*dmVdz-dmVde(i,j  ,k1))+  &
     &                           cff1*(tl_cff1*dmVdz+cff1*tl_dmVdz-     &
     &                                 tl_dmVde(i,j-1,k1))+             &
     &                           cff2*(tl_cff2*dmVdz+cff2*tl_dmVdz-     &
     &                                 tl_dmVde(i,j  ,k2))+             &
     &                           cff3*(tl_cff3*dmVdz+cff3*tl_dmVdz-     &
     &                                 tl_dmVde(i,j-1,k2))+             &
     &                           cff4*(tl_cff4*dmVdz+cff4*tl_dmVdz-     &
     &                                 tl_dmVde(i,j  ,k1)))
#ifdef VISC_3DCOEF
                tl_VFse(i,j,k2)=tl_VFse(i,j,k2)+                        &
     &                          tl_fac2*                                &
     &                          (cff1*(cff1*dmVdz-dmVde(i,j-1,k1))+     &
     &                           cff2*(cff2*dmVdz-dmVde(i,j  ,k2))+     &
     &                           cff3*(cff3*dmVdz-dmVde(i,j-1,k2))+     &
     &                           cff4*(cff4*dmVdz-dmVde(i,j  ,k1)))
#endif

                cff1=MIN(dZde_r(i,j-1,k1),0.0_r8)
                cff2=MIN(dZde_r(i,j  ,k2),0.0_r8)
                cff3=MAX(dZde_r(i,j-1,k2),0.0_r8)
                cff4=MAX(dZde_r(i,j  ,k1),0.0_r8)
                cff5=MIN(dZdx_r(i,j-1,k1),0.0_r8)
                cff6=MIN(dZdx_r(i,j  ,k2),0.0_r8)
                cff7=MAX(dZdx_r(i,j-1,k2),0.0_r8)
                cff8=MAX(dZdx_r(i,j  ,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j-1,k1)))*        &
     &                  tl_dZde_r(i,j-1,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j  ,k2)))*        &
     &                  tl_dZde_r(i,j  ,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j-1,k2)))*        &
     &                  tl_dZde_r(i,j-1,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j  ,k1)))*        &
     &                  tl_dZde_r(i,j  ,k1)
                tl_cff5=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i,j-1,k1)))*        &
     &                  tl_dZdx_r(i,j-1,k1)
                tl_cff6=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i,j  ,k2)))*        &
     &                  tl_dZdx_r(i,j  ,k2)
                tl_cff7=(0.5_r8+SIGN(0.5_r8, dZdx_r(i,j-1,k2)))*        &
     &                  tl_dZdx_r(i,j-1,k2)
                tl_cff8=(0.5_r8+SIGN(0.5_r8, dZdx_r(i,j  ,k1)))*        &
     &                  tl_dZdx_r(i,j  ,k1)
                VFsx(i,j,k2)=VFsx(i,j,k2)-                              &
     &                       fac1*                                      &
     &                       (cff1*(cff5*dnUdz-dnUdx(i,j-1,k1))+        &
     &                        cff2*(cff6*dnUdz-dnUdx(i,j  ,k2))+        &
     &                        cff3*(cff7*dnUdz-dnUdx(i,j-1,k2))+        &
     &                        cff4*(cff8*dnUdz-dnUdx(i,j  ,k1)))
                tl_VFsx(i,j,k2)=tl_VFsx(i,j,k2)-                        &
     &                          fac1*                                   &
     &                          (tl_cff1*(cff5*dnUdz-dnUdx(i,j-1,k1))+  &
     &                           tl_cff2*(cff6*dnUdz-dnUdx(i,j  ,k2))+  &
     &                           tl_cff3*(cff7*dnUdz-dnUdx(i,j-1,k2))+  &
     &                           tl_cff4*(cff8*dnUdz-dnUdx(i,j  ,k1))+  &
     &                           cff1*(tl_cff5*dnUdz+cff5*tl_dnUdz-     &
     &                                 tl_dnUdx(i,j-1,k1))+             &
     &                           cff2*(tl_cff6*dnUdz+cff6*tl_dnUdz-     &
     &                                 tl_dnUdx(i,j  ,k2))+             &
     &                           cff3*(tl_cff7*dnUdz+cff7*tl_dnUdz-     &
     &                                 tl_dnUdx(i,j-1,k2))+             &
     &                           cff4*(tl_cff8*dnUdz+cff8*tl_dnUdz-     &
     &                                 tl_dnUdx(i,j  ,k1)))
#ifdef VISC_3DCOEF
                tl_VFsx(i,j,k2)=tl_VFsx(i,j,k2)-                        &
     &                          tl_fac1*                                &
     &                          (cff1*(cff5*dnUdz-dnUdx(i,j-1,k1))+     &
     &                           cff2*(cff6*dnUdz-dnUdx(i,j  ,k2))+     &
     &                           cff3*(cff7*dnUdz-dnUdx(i,j-1,k2))+     &
     &                           cff4*(cff8*dnUdz-dnUdx(i,j  ,k1)))
#endif

                cff1=MIN(dZdx_p(i  ,j,k1),0.0_r8)
                cff2=MIN(dZdx_p(i+1,j,k2),0.0_r8)
                cff3=MAX(dZdx_p(i  ,j,k2),0.0_r8)
                cff4=MAX(dZdx_p(i+1,j,k1),0.0_r8)
                cff5=MIN(dZde_p(i  ,j,k1),0.0_r8)
                cff6=MIN(dZde_p(i+1,j,k2),0.0_r8)
                cff7=MAX(dZde_p(i  ,j,k2),0.0_r8)
                cff8=MAX(dZde_p(i+1,j,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i  ,j,k1)))*        &
     &                  tl_dZdx_p(i  ,j,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i+1,j,k2)))*        &
     &                  tl_dZdx_p(i+1,j,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZdx_p(i  ,j,k2)))*        &
     &                  tl_dZdx_p(i  ,j,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZdx_p(i+1,j,k1)))*        &
     &                  tl_dZdx_p(i+1,j,k1)
                tl_cff5=(0.5_r8+SIGN(0.5_r8,-dZde_p(i  ,j,k1)))*        &
     &                  tl_dZde_p(i  ,j,k1)
                tl_cff6=(0.5_r8+SIGN(0.5_r8,-dZde_p(i+1,j,k2)))*        &
     &                  tl_dZde_p(i+1,j,k2)
                tl_cff7=(0.5_r8+SIGN(0.5_r8, dZde_p(i  ,j,k2)))*        &
     &                  tl_dZde_p(i  ,j,k2)
                tl_cff8=(0.5_r8+SIGN(0.5_r8, dZde_p(i+1,j,k1)))*        &
     &                  tl_dZde_p(i+1,j,k1)
                VFse(i,j,k2)=VFse(i,j,k2)+                              &
     &                       fac2*                                      &
     &                       (cff1*(cff5*dmUdz-dmUde(i  ,j,k1))+        &
     &                        cff2*(cff6*dmUdz-dmUde(i+1,j,k2))+        &
     &                        cff3*(cff7*dmUdz-dmUde(i  ,j,k2))+        &
     &                        cff4*(cff8*dmUdz-dmUde(i+1,j,k1)))
                tl_VFse(i,j,k2)=tl_VFse(i,j,k2)+                        &
     &                          fac2*                                   &
     &                          (tl_cff1*(cff5*dmUdz-dmUde(i  ,j,k1))+  &
     &                           tl_cff2*(cff6*dmUdz-dmUde(i+1,j,k2))+  &
     &                           tl_cff3*(cff7*dmUdz-dmUde(i  ,j,k2))+  &
     &                           tl_cff4*(cff8*dmUdz-dmUde(i+1,j,k1))+  &
     &                           cff1*(tl_cff5*dmUdz+cff5*tl_dmUdz-     &
     &                                 tl_dmUde(i  ,j,k1))+             &
     &                           cff2*(tl_cff6*dmUdz+cff6*tl_dmUdz-     &
     &                                 tl_dmUde(i+1,j,k2))+             &
     &                           cff3*(tl_cff7*dmUdz+cff7*tl_dmUdz-     &
     &                                 tl_dmUde(i  ,j,k2))+             &
     &                           cff4*(tl_cff8*dmUdz+cff8*tl_dmUdz-     &
     &                                 tl_dmUde(i+1,j,k1)))
#ifdef VISC_3DCOEF
                tl_VFse(i,j,k2)=tl_VFse(i,j,k2)+                        &
     &                          tl_fac2*                                &
     &                          (cff1*(cff5*dmUdz-dmUde(i  ,j,k1))+     &
     &                           cff2*(cff6*dmUdz-dmUde(i+1,j,k2))+     &
     &                           cff3*(cff7*dmUdz-dmUde(i  ,j,k2))+     &
     &                           cff4*(cff8*dmUdz-dmUde(i+1,j,k1)))
#endif
              END DO
            END DO
          END IF
!
!  Compute first harmonic operator (m s^-3/2).
!
          DO j=Jstrm1,Jendp1
            DO i=IstrUm1,Iendp1
              cff=0.125_r8*(pm(i-1,j)+pm(i,j))*                         &
     &                     (pn(i-1,j)+pn(i,j))
              cff1=1.0_r8/(0.5_r8*(Hz(i-1,j,k)+Hz(i,j,k)))
              tl_cff1=-cff1*cff1*                                       &
     &                (0.5_r8*(tl_Hz(i-1,j,k)+tl_Hz(i,j,k)))
              LapU(i,j,k)=cff*((pn(i-1,j)+pn(i,j))*                     &
                               (UFx(i,j)-UFx(i-1,j))+                   &
     &                         (pm(i-1,j)+pm(i,j))*                     &
     &                         (UFe(i,j+1)-UFe(i,j)))+                  &
     &                    cff1*((UFsx(i,j,k2)+UFse(i,j,k2))-            &
     &                          (UFsx(i,j,k1)+UFse(i,j,k1)))
              tl_LapU(i,j,k)=cff*((pn(i-1,j)+pn(i,j))*                  &
                                  (tl_UFx(i,j)-tl_UFx(i-1,j))+          &
     &                            (pm(i-1,j)+pm(i,j))*                  &
     &                            (tl_UFe(i,j+1)-tl_UFe(i,j)))+         &
     &                       tl_cff1*((UFsx(i,j,k2)+UFse(i,j,k2))-      &
     &                                (UFsx(i,j,k1)+UFse(i,j,k1)))+     &
     &                       cff1*((tl_UFsx(i,j,k2)+tl_UFse(i,j,k2))-   &
     &                             (tl_UFsx(i,j,k1)+tl_UFse(i,j,k1)))
#ifdef MASKING
              LapU(i,j,k)=LapU(i,j,k)*umask(i,j)
              tl_LapU(i,j,k)=tl_LapU(i,j,k)*umask(i,j)
#endif
            END DO
          END DO

          DO j=JstrVm1,Jendp1
            DO i=Istrm1,Iendp1
              cff=0.125_r8*(pm(i,j)+pm(i,j-1))*                         &
     &                     (pn(i,j)+pn(i,j-1))
              cff1=1.0_r8/(0.5_r8*(Hz(i,j-1,k)+Hz(i,j,k)))
              tl_cff1=-cff1*cff1*                                       &
     &                (0.5_r8*(tl_Hz(i,j-1,k)+tl_Hz(i,j,k)))
              LapV(i,j,k)=cff*((pn(i,j-1)+pn(i,j))*                     &
     &                         (VFx(i+1,j)-VFx(i,j))-                   &
     &                         (pm(i,j-1)+pm(i,j))*                     &
     &                         (VFe(i,j)-VFe(i,j-1)))+                  &
     &                    cff1*((VFsx(i,j,k2)+VFse(i,j,k2))-            &
     &                          (VFsx(i,j,k1)+VFse(i,j,k1)))
              tl_LapV(i,j,k)=cff*((pn(i,j-1)+pn(i,j))*                  &
     &                            (tl_VFx(i+1,j)-tl_VFx(i,j))-          &
     &                            (pm(i,j-1)+pm(i,j))*                  &
     &                            (tl_VFe(i,j)-tl_VFe(i,j-1)))+         &
     &                       tl_cff1*((VFsx(i,j,k2)+VFse(i,j,k2))-      &
     &                                (VFsx(i,j,k1)+VFse(i,j,k1)))+     &
     &                       cff1*((tl_VFsx(i,j,k2)+tl_VFse(i,j,k2))-   &
     &                             (tl_VFsx(i,j,k1)+tl_VFse(i,j,k1)))
#ifdef MASKING
              LapV(i,j,k)=LapV(i,j,k)*vmask(i,j)
              tl_LapV(i,j,k)=tl_LapV(i,j,k)*vmask(i,j)
#endif
            END DO
          END DO
        END IF
      END DO K_LOOP1
!
!  Apply boundary conditions (closed or gradient; except periodic)
!  to the first harmonic operator.
!
      IF (.not.(CompositeGrid(iwest,ng).or.EWperiodic(ng))) THEN
        IF (DOMAIN(ng)%Western_Edge(tile)) THEN
          IF (tl_LBC(iwest,isUvel,ng)%closed) THEN
            DO k=1,N(ng)
              DO j=Jstrm1,Jendp1
                LapU(IstrU-1,j,k)=0.0_r8
                tl_LapU(IstrU-1,j,k)=0.0_r8
              END DO
            END DO
          ELSE
            DO k=1,N(ng)
              DO j=Jstrm1,Jendp1
                LapU(IstrU-1,j,k)=LapU(IstrU,j,k)
                tl_LapU(IstrU-1,j,k)=tl_LapU(IstrU,j,k)
              END DO
            END DO
          END IF
          IF (tl_LBC(iwest,isVvel,ng)%closed) THEN
            DO k=1,N(ng)
              DO j=JstrVm1,Jendp1
                LapV(Istr-1,j,k)=gamma2(ng)*LapV(Istr,j,k)
                tl_LapV(Istr-1,j,k)=gamma2(ng)*tl_LapV(Istr,j,k)
              END DO
            END DO
          ELSE
            DO k=1,N(ng)
              DO j=JstrVm1,Jendp1
                LapV(Istr-1,j,k)=0.0_r8
                tl_LapV(Istr-1,j,k)=0.0_r8
              END DO
            END DO
          END IF
        END IF
      END IF
!
      IF (.not.(CompositeGrid(ieast,ng).or.EWperiodic(ng))) THEN
        IF (DOMAIN(ng)%Eastern_Edge(tile)) THEN
          IF (tl_LBC(ieast,isUvel,ng)%closed) THEN
            DO k=1,N(ng)
              DO j=Jstrm1,Jendp1
                LapU(Iend+1,j,k)=0.0_r8
                tl_LapU(Iend+1,j,k)=0.0_r8
              END DO
            END DO
          ELSE
            DO k=1,N(ng)
              DO j=Jstrm1,Jendp1
                LapU(Iend+1,j,k)=LapU(Iend,j,k)
                tl_LapU(Iend+1,j,k)=tl_LapU(Iend,j,k)
              END DO
            END DO
          END IF
          IF (tl_LBC(ieast,isVvel,ng)%closed) THEN
            DO k=1,N(ng)
              DO j=JstrVm1,Jendp1
                LapV(Iend+1,j,k)=gamma2(ng)*LapV(Iend,j,k)
                tl_LapV(Iend+1,j,k)=gamma2(ng)*tl_LapV(Iend,j,k)
              END DO
            END DO
          ELSE
            DO k=1,N(ng)
              DO j=JstrVm1,Jendp1
                LapV(Iend+1,j,k)=0.0_r8
                tl_LapV(Iend+1,j,k)=0.0_r8
              END DO
            END DO
          END IF
        END IF
      END IF
!
      IF (.not.(CompositeGrid(isouth,ng).or.NSperiodic(ng))) THEN
        IF (DOMAIN(ng)%Southern_Edge(tile)) THEN
          IF (tl_LBC(isouth,isUvel,ng)%closed) THEN
            DO k=1,N(ng)
              DO i=IstrUm1,Iendp1
                LapU(i,Jstr-1,k)=gamma2(ng)*LapU(i,Jstr,k)
                tl_LapU(i,Jstr-1,k)=gamma2(ng)*tl_LapU(i,Jstr,k)
              END DO
            END DO
          ELSE
            DO k=1,N(ng)
              DO i=IstrUm1,Iendp1
                LapU(i,Jstr-1,k)=0.0_r8
                tl_LapU(i,Jstr-1,k)=0.0_r8
              END DO
            END DO
          END IF
          IF (tl_LBC(isouth,isVvel,ng)%closed) THEN
            DO k=1,N(ng)
              DO i=Istrm1,Iendp1
                LapV(i,JstrV-1,k)=0.0_r8
                tl_LapV(i,JstrV-1,k)=0.0_r8
              END DO
            END DO
          ELSE
            DO k=1,N(ng)
              DO i=Istrm1,Iendp1
                LapV(i,JstrV-1,k)=LapV(i,JstrV,k)
                tl_LapV(i,JstrV-1,k)=tl_LapV(i,JstrV,k)
              END DO
            END DO
          END IF
        END IF
      END IF
!
      IF (.not.(CompositeGrid(inorth,ng).or.NSperiodic(ng))) THEN
        IF (DOMAIN(ng)%Northern_Edge(tile)) THEN
          IF (tl_LBC(inorth,isUvel,ng)%closed) THEN
            DO k=1,N(ng)
              DO i=IstrUm1,Iendp1
                LapU(i,Jend+1,k)=gamma2(ng)*LapU(i,Jend,k)
                tl_LapU(i,Jend+1,k)=gamma2(ng)*tl_LapU(i,Jend,k)
              END DO
            END DO
          ELSE
            DO k=1,N(ng)
              DO i=IstrUm1,Iendp1
                LapU(i,Jend+1,k)=0.0_r8
                tl_LapU(i,Jend+1,k)=0.0_r8
              END DO
            END DO
          END IF
          IF (tl_LBC(inorth,isVvel,ng)%closed) THEN
            DO k=1,N(ng)
              DO i=Istrm1,Iendp1
                LapV(i,Jend+1,k)=0.0_r8
                tl_LapV(i,Jend+1,k)=0.0_r8
              END DO
            END DO
          ELSE
            DO k=1,N(ng)
              DO i=Istrm1,Iendp1
                LapV(i,Jend+1,k)=LapV(i,Jend,k)
                tl_LapV(i,Jend+1,k)=tl_LapV(i,Jend,k)
              END DO
            END DO
          END IF
        END IF
      END IF
!
      IF (.not.(CompositeGrid(isouth,ng).or.NSperiodic(ng).or.          &
     &          CompositeGrid(iwest ,ng).or.EWperiodic(ng))) THEN
        IF (DOMAIN(ng)%SouthWest_Corner(tile)) THEN
          DO k=1,N(ng)
            LapU(Istr  ,Jstr-1,k)=0.5_r8*                               &
     &                            (LapU(Istr+1,Jstr-1,k)+               &
     &                             LapU(Istr  ,Jstr  ,k))
            tl_LapU(Istr  ,Jstr-1,k)=0.5_r8*                            &
     &                               (tl_LapU(Istr+1,Jstr-1,k)+         &
     &                                tl_LapU(Istr  ,Jstr  ,k))
            LapV(Istr-1,Jstr  ,k)=0.5_r8*                               &
     &                            (LapV(Istr-1,Jstr+1,k)+               &
     &                             LapV(Istr  ,Jstr  ,k))
            tl_LapV(Istr-1,Jstr  ,k)=0.5_r8*                            &
     &                               (tl_LapV(Istr-1,Jstr+1,k)+         &
     &                                tl_LapV(Istr  ,Jstr  ,k))
          END DO
        END IF
      END IF

      IF (.not.(CompositeGrid(isouth,ng).or.NSperiodic(ng).or.          &
     &          CompositeGrid(ieast ,ng).or.EWperiodic(ng))) THEN
        IF (DOMAIN(ng)%SouthEast_Corner(tile)) THEN
          DO k=1,N(ng)
            LapU(Iend+1,Jstr-1,k)=0.5_r8*                               &
     &                            (LapU(Iend  ,Jstr-1,k)+               &
     &                             LapU(Iend+1,Jstr  ,k))
            tl_LapU(Iend+1,Jstr-1,k)=0.5_r8*                            &
     &                               (tl_LapU(Iend  ,Jstr-1,k)+         &
     &                                tl_LapU(Iend+1,Jstr  ,k))
            LapV(Iend+1,Jstr  ,k)=0.5_r8*                               &
     &                            (LapV(Iend  ,Jstr  ,k)+               &
     &                             LapV(Iend+1,Jstr+1,k))
            tl_LapV(Iend+1,Jstr  ,k)=0.5_r8*                            &
     &                               (tl_LapV(Iend  ,Jstr  ,k)+         &
     &                                tl_LapV(Iend+1,Jstr+1,k))
          END DO
        END IF
      END IF

      IF (.not.(CompositeGrid(inorth,ng).or.NSperiodic(ng).or.          &
     &          CompositeGrid(iwest ,ng).or.EWperiodic(ng))) THEN
        IF (DOMAIN(ng)%NorthWest_Corner(tile)) THEN
          DO k=1,N(ng)
            LapU(Istr  ,Jend+1,k)=0.5_r8*                               &
     &                            (LapU(Istr+1,Jend+1,k)+               &
     &                             LapU(Istr  ,Jend  ,k))
            tl_LapU(Istr  ,Jend+1,k)=0.5_r8*                            &
     &                               (tl_LapU(Istr+1,Jend+1,k)+         &
     &                                tl_LapU(Istr  ,Jend  ,k))
            LapV(Istr-1,Jend+1,k)=0.5_r8*                               &
     &                            (LapV(Istr  ,Jend+1,k)+               &
     &                             LapV(Istr-1,Jend  ,k))
            tl_LapV(Istr-1,Jend+1,k)=0.5_r8*                            &
     &                               (tl_LapV(Istr  ,Jend+1,k)+         &
     &                                tl_LapV(Istr-1,Jend  ,k))
          END DO
        END IF
      END IF

      IF (.not.(CompositeGrid(inorth,ng).or.NSperiodic(ng).or.          &
     &          CompositeGrid(ieast ,ng).or.EWperiodic(ng))) THEN
        IF (DOMAIN(ng)%NorthEast_Corner(tile)) THEN
          DO k=1,N(ng)
            LapU(Iend+1,Jend+1,k)=0.5_r8*                               &
     &                            (LapU(Iend  ,Jend+1,k)+               &
     &                             LapU(Iend+1,Jend  ,k))
            tl_LapU(Iend+1,Jend+1,k)=0.5_r8*                            &
     &                               (tl_LapU(Iend  ,Jend+1,k)+         &
     &                                tl_LapU(Iend+1,Jend  ,k))
            LapV(Iend+1,Jend+1,k)=0.5_r8*                               &
     &                            (LapV(Iend  ,Jend+1,k)+               &
     &                             LapV(Iend+1,Jend  ,k))
            tl_LapV(Iend+1,Jend+1,k)=0.5_r8*                            &
     &                               (tl_LapV(Iend  ,Jend+1,k)+         &
     &                                tl_LapV(Iend+1,Jend  ,k))
          END DO
        END IF
      END IF
!
!  Compute horizontal and vertical gradients associated with the
!  second rotated harmonic operator.
!
      k2=1
      K_LOOP2 : DO k=0,N(ng)
        k1=k2
        k2=3-k1
        IF (k.lt.N(ng)) THEN
!
!  Compute slopes (nondimensional) at RHO- and PSI-points.
!
          DO j=Jstr-1,Jend+1
            DO i=IstrU-1,Iend+1
              cff=0.5_r8*(pm(i-1,j)+pm(i,j))
#ifdef MASKING
              cff=cff*umask(i,j)
#endif
              UFx(i,j)=cff*(z_r(i  ,j,k+1)-                             &
     &                      z_r(i-1,j,k+1))
              tl_UFx(i,j)=cff*(tl_z_r(i  ,j,k+1)-                       &
     &                         tl_z_r(i-1,j,k+1))
            END DO
          END DO
          DO j=JstrV-1,Jend+1
            DO i=Istr-1,Iend+1
              cff=0.5_r8*(pn(i,j-1)+pn(i,j))
#ifdef MASKING
              cff=cff*vmask(i,j)
#endif
              VFe(i,j)=cff*(z_r(i,j  ,k+1)-                             &
     &                      z_r(i,j-1,k+1))
              tl_VFe(i,j)=cff*(tl_z_r(i,j  ,k+1)-                       &
     &                         tl_z_r(i,j-1,k+1))
            END DO
          END DO
!
          DO j=Jstr,Jend+1
            DO i=Istr,Iend+1
              dZdx_p(i,j,k2)=0.5_r8*(UFx(i,j-1)+                        &
     &                               UFx(i,j  ))
              tl_dZdx_p(i,j,k2)=0.5_r8*(tl_UFx(i,j-1)+                  &
     &                                  tl_UFx(i,j  ))
              dZde_p(i,j,k2)=0.5_r8*(VFe(i-1,j)+                        &
     &                               VFe(i  ,j))
              tl_dZde_p(i,j,k2)=0.5_r8*(tl_VFe(i-1,j)+                  &
     &                                  tl_VFe(i  ,j))
            END DO
          END DO
          DO j=JstrV-1,Jend
            DO i=IstrU-1,Iend
              dZdx_r(i,j,k2)=0.5_r8*(UFx(i  ,j)+                        &
     &                               UFx(i+1,j))
              tl_dZdx_r(i,j,k2)=0.5_r8*(tl_UFx(i  ,j)+                  &
     &                                  tl_UFx(i+1,j))
              dZde_r(i,j,k2)=0.5_r8*(VFe(i,j  )+                        &
     &                               VFe(i,j+1))
              tl_dZde_r(i,j,k2)=0.5_r8*(tl_VFe(i,j  )+                  &
     &                                  tl_VFe(i,j+1))
            END DO
          END DO
!
!  Compute momentum horizontal (m^-1 s^-3/2) and vertical (s^-3/2)
!  gradients.
!
          DO j=JstrV-1,Jend
            DO i=IstrU-1,Iend
              cff=0.5_r8*pm(i,j)
#ifdef MASKING
              cff=cff*rmask(i,j)
#endif
              dnUdx(i,j,k2)=cff*((pn(i  ,j)+pn(i+1,j))*                 &
     &                           LapU(i+1,j,k+1)-                       &
     &                           (pn(i-1,j)+pn(i  ,j))*                 &
     &                           LapU(i  ,j,k+1))
              tl_dnUdx(i,j,k2)=cff*((pn(i  ,j)+pn(i+1,j))*              &
     &                              tl_LapU(i+1,j,k+1)-                 &
     &                              (pn(i-1,j)+pn(i  ,j))*              &
     &                              tl_LapU(i  ,j,k+1))
            END DO
          END DO

          DO j=Jstr,Jend+1
            DO i=Istr,Iend+1
              cff=0.125_r8*(pn(i-1,j  )+pn(i,j  )+                      &
     &                      pn(i-1,j-1)+pn(i,j-1))
#ifdef MASKING
              cff=cff*pmask(i,j)
#endif
              dmUde(i,j,k2)=cff*((pm(i-1,j  )+pm(i,j  ))*               &
     &                           LapU(i,j  ,k+1)-                       &
     &                           (pm(i-1,j-1)+pm(i,j-1))*               &
     &                           LapU(i,j-1,k+1))
              tl_dmUde(i,j,k2)=cff*((pm(i-1,j  )+pm(i,j  ))*            &
     &                              tl_LapU(i,j  ,k+1)-                 &
     &                              (pm(i-1,j-1)+pm(i,j-1))*            &
     &                              tl_LapU(i,j-1,k+1))
            END DO
          END DO

          DO j=Jstr,Jend+1
            DO i=Istr,Iend+1
              cff=0.125_r8*(pm(i-1,j  )+pm(i,j  )+                      &
     &                      pm(i-1,j-1)+pm(i,j-1))
#ifdef MASKING
              cff=cff*pmask(i,j)
#endif
              dnVdx(i,j,k2)=cff*((pn(i  ,j-1)+pn(i  ,j))*               &
     &                           LapV(i  ,j,k+1)-                       &
     &                           (pn(i-1,j-1)+pn(i-1,j))*               &
     &                           LapV(i-1,j,k+1))
              tl_dnVdx(i,j,k2)=cff*((pn(i  ,j-1)+pn(i  ,j))*            &
     &                              tl_LapV(i  ,j,k+1)-                 &
     &                              (pn(i-1,j-1)+pn(i-1,j))*            &
     &                              tl_LapV(i-1,j,k+1))
            END DO
          END DO

          DO j=JstrV-1,Jend
            DO i=IstrU-1,Iend
              cff=0.5_r8*pn(i,j)
#ifdef MASKING
              cff=cff*rmask(i,j)
#endif
              dmVde(i,j,k2)=cff*((pm(i,j  )+pm(i,j+1))*                 &
     &                           LapV(i,j+1,k+1)-                       &
     &                           (pm(i,j-1)+pm(i,j  ))*                 &
     &                           LapV(i,j  ,k+1))
              tl_dmVde(i,j,k2)=cff*((pm(i,j  )+pm(i,j+1))*              &
     &                              tl_LapV(i,j+1,k+1)-                 &
     &                              (pm(i,j-1)+pm(i,j  ))*              &
     &                              tl_LapV(i,j  ,k+1))
            END DO
          END DO
        END IF

        IF ((k.eq.0).or.(k.eq.N(ng))) THEN
          DO j=Jstr-1,Jend+1
            DO i=IstrU-1,Iend+1
              dUdz(i,j,k2)=0.0_r8
              tl_dUdz(i,j,k2)=0.0_r8
            END DO
          END DO
          DO j=JstrV-1,Jend+1
            DO i=Istr-1,Iend+1
              dVdz(i,j,k2)=0.0_r8
              tl_dVdz(i,j,k2)=0.0_r8
            END DO
          END DO

          DO j=Jstr,Jend
            DO i=IstrU,Iend
              UFsx(i,j,k2)=0.0_r8
              tl_UFsx(i,j,k2)=0.0_r8
              UFse(i,j,k2)=0.0_r8
              tl_UFse(i,j,k2)=0.0_r8
            END DO
          END DO
          DO j=JstrV,Jend
            DO i=Istr,Iend
              VFsx(i,j,k2)=0.0_r8
              tl_VFsx(i,j,k2)=0.0_r8
              VFse(i,j,k2)=0.0_r8
              tl_VFse(i,j,k2)=0.0_r8
            END DO
          END DO
        ELSE
          DO j=Jstr-1,Jend+1
            DO i=IstrU-1,Iend+1
              cff=1.0_r8/(0.5_r8*(z_r(i-1,j,k+1)-                       &
     &                            z_r(i-1,j,k  )+                       &
     &                            z_r(i  ,j,k+1)-                       &
     &                            z_r(i  ,j,k  )))
              tl_cff=-cff*cff*(0.5_r8*(tl_z_r(i-1,j,k+1)-               &
     &                                 tl_z_r(i-1,j,k  )+               &
     &                                 tl_z_r(i  ,j,k+1)-               &
     &                                 tl_z_r(i  ,j,k  )))
              dUdz(i,j,k2)=cff*(LapU(i,j,k+1)-                          &
     &                          LapU(i,j,k  ))
              tl_dUdz(i,j,k2)=tl_cff*(LapU(i,j,k+1)-                    &
     &                                LapU(i,j,k  ))+                   &
     &                        cff*(tl_LapU(i,j,k+1)-                    &
     &                             tl_LapU(i,j,k  ))
            END DO
          END DO
          DO j=JstrV-1,Jend+1
            DO i=Istr-1,Iend+1
              cff=1.0_r8/(0.5_r8*(z_r(i,j-1,k+1)-                       &
     &                            z_r(i,j-1,k  )+                       &
     &                            z_r(i,j  ,k+1)-                       &
     &                            z_r(i,j  ,k  )))
              tl_cff=-cff*cff*(0.5_r8*(tl_z_r(i,j-1,k+1)-               &
     &                                 tl_z_r(i,j-1,k  )+               &
     &                                 tl_z_r(i,j  ,k+1)-               &
     &                                 tl_z_r(i,j  ,k  )))
              dVdz(i,j,k2)=cff*(LapV(i,j,k+1)-                          &
     &                          LapV(i,j,k  ))
              tl_dVdz(i,j,k2)=tl_cff*(LapV(i,j,k+1)-                    &
     &                                LapV(i,j,k  ))+                   &
     &                        cff*(tl_LapV(i,j,k+1)-                    &
     &                             tl_LapV(i,j,k  ))
            END DO
          END DO
        END IF
!
!  Compute components of the rotated viscous flux (m5/s2) along
!  geopotential surfaces in the XI- and ETA-directions.
!
        IF (k.gt.0) THEN
          DO j=JstrV-1,Jend
            DO i=IstrU-1,Iend
              cff1=MIN(dZdx_r(i,j,k1),0.0_r8)
              cff2=MAX(dZdx_r(i,j,k1),0.0_r8)
              cff3=MIN(dZde_r(i,j,k1),0.0_r8)
              cff4=MAX(dZde_r(i,j,k1),0.0_r8)
              tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i,j,k1)))*            &
     &                tl_dZdx_r(i,j,k1)
              tl_cff2=(0.5_r8+SIGN(0.5_r8, dZdx_r(i,j,k1)))*            &
     &                tl_dZdx_r(i,j,k1)
              tl_cff3=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j,k1)))*            &
     &                tl_dZde_r(i,j,k1)
              tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j,k1)))*            &
     &                tl_dZde_r(i,j,k1)
#ifdef VISC_3DCOEF
              cff=Hz(i,j,k)*                                            &
     &            (on_r(i,j)*(dnUdx(i,j,k1)-                            &
     &                        0.5_r8*pn(i,j)*                           &
     &                        (cff1*(dUdz(i  ,j,k1)+                    &
     &                               dUdz(i+1,j,k2))+                   &
     &                         cff2*(dUdz(i  ,j,k2)+                    &
     &                               dUdz(i+1,j,k1))))-                 &
     &             om_r(i,j)*(dmVde(i,j,k1)-                            &
     &                        0.5_r8*pm(i,j)*                           &
     &                        (cff3*(dVdz(i,j  ,k1)+                    &
     &                               dVdz(i,j+1,k2))+                   &
     &                         cff4*(dVdz(i,j  ,k2)+                    &
     &                               dVdz(i,j+1,k1)))))
#else
!>            cff=Hz(i,j,k)*                                            &
!>   &            (on_r(i,j)*(dnUdx(i,j,k1)-                            &
!>   &                        0.5_r8*pn(i,j)*                           &
!>   &                        (cff1*(dUdz(i  ,j,k1)+                    &
!>   &                               dUdz(i+1,j,k2))+                   &
!>   &                         cff2*(dUdz(i  ,j,k2)+                    &
!>   &                               dUdz(i+1,j,k1))))-                 &
!>   &             om_r(i,j)*(dmVde(i,j,k1)-                            &
!>   &                        0.5_r8*pm(i,j)*                           &
!>   &                        (cff3*(dVdz(i,j  ,k1)+                    &
!>   &                               dVdz(i,j+1,k2))+                   &
!>   &                         cff4*(dVdz(i,j  ,k2)+                    &
!>   &                               dVdz(i,j+1,k1)))))
!>
#endif
              tl_cff=tl_Hz(i,j,k)*                                      &
     &               (on_r(i,j)*(dnUdx(i,j,k1)-                         &
     &                           0.5_r8*pn(i,j)*                        &
     &                           (cff1*(dUdz(i  ,j,k1)+                 &
     &                                  dUdz(i+1,j,k2))+                &
     &                            cff2*(dUdz(i  ,j,k2)+                 &
     &                                  dUdz(i+1,j,k1))))-              &
     &                om_r(i,j)*(dmVde(i,j,k1)-                         &
     &                           0.5_r8*pm(i,j)*                        &
     &                           (cff3*(dVdz(i,j  ,k1)+                 &
     &                                  dVdz(i,j+1,k2))+                &
     &                            cff4*(dVdz(i,j  ,k2)+                 &
     &                                  dVdz(i,j+1,k1)))))+             &
     &                Hz(i,j,k)*                                        &
     &                (on_r(i,j)*(tl_dnUdx(i,j,k1)-                     &
     &                            0.5_r8*pn(i,j)*                       &
     &                            (tl_cff1*(dUdz(i  ,j,k1)+             &
     &                                      dUdz(i+1,j,k2))+            &
     &                             cff1*(tl_dUdz(i  ,j,k1)+             &
     &                                   tl_dUdz(i+1,j,k2))+            &
     &                             tl_cff2*(dUdz(i  ,j,k2)+             &
     &                                      dUdz(i+1,j,k1))+            &
     &                             cff2*(tl_dUdz(i  ,j,k2)+             &
     &                                   tl_dUdz(i+1,j,k1))))-          &
     &                 om_r(i,j)*(tl_dmVde(i,j,k1)-                     &
     &                            0.5_r8*pm(i,j)*                       &
     &                            (tl_cff3*(dVdz(i,j  ,k1)+             &
     &                                      dVdz(i,j+1,k2))+            &
     &                             cff3*(tl_dVdz(i,j  ,k1)+             &
     &                                   tl_dVdz(i,j+1,k2))+            &
     &                             tl_cff4*(dVdz(i,j  ,k2)+             &
     &                                      dVdz(i,j+1,k1))+            &
     &                             cff4*(tl_dVdz(i,j  ,k2)+             &
     &                                   tl_dVdz(i,j+1,k1)))))
#ifdef MASKING
# ifdef VISC_3DCOEF
              cff=cff*rmask(i,j)
# else
!>            cff=cff*rmask(i,j)
!>
# endif
              tl_cff=tl_cff*rmask(i,j)
#endif
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
!>            UFx(i,j)=on_r(i,j)*on_r(i,j)*Uvis3d_r(i,j,k)*cff
!>
              tl_UFx(i,j)=on_r(i,j)*on_r(i,j)*                          &
     &                    (tl_Uvis3d_r(i,j,k)*cff+                      &
     &                     Uvis3d_r(i,j,k)*tl_cff)
!>            VFe(i,j)=om_r(i,j)*om_r(i,j)*Vvis3d_r(i,j,k)*cff
!>
              tl_VFe(i,j)=om_r(i,j)*om_r(i,j)*                          &
     &                    (tl_Vvis3d_r(i,j,k)*cff+                      &
     &                     Vvis3d_r(i,j,k)*tl_cff)
# else
!>            UFx(i,j)=on_r(i,j)*on_r(i,j)*visc3d_r(i,j,k)*cff
!>
              tl_UFx(i,j)=on_r(i,j)*on_r(i,j)*                          &
     &                    (tl_visc3d_r(i,j,k)*cff+                      &
     &                     visc3d_r(i,j,k)*tl_cff)
!>            VFe(i,j)=om_r(i,j)*om_r(i,j)*visc3d_r(i,j,k)*cff
!>
              tl_VFe(i,j)=om_r(i,j)*om_r(i,j)*                          &
     &                    (tl_visc3d_r(i,j,k)*cff+                      &
     &                     visc3d_r(i,j,k)*tl_cff)
# endif
#else
!>            UFx(i,j)=on_r(i,j)*on_r(i,j)*visc4_r(i,j)*cff
!>
              tl_UFx(i,j)=on_r(i,j)*on_r(i,j)*visc4_r(i,j)*tl_cff
!>            VFe(i,j)=om_r(i,j)*om_r(i,j)*visc4_r(i,j)*cff
!>
              tl_VFe(i,j)=om_r(i,j)*om_r(i,j)*visc4_r(i,j)*tl_cff
#endif
            END DO
          END DO

          DO j=Jstr,Jend+1
            DO i=Istr,Iend+1
              pm_p=0.25_r8*(pm(i-1,j-1)+pm(i-1,j)+                      &
     &                      pm(i  ,j-1)+pm(i  ,j))
              pn_p=0.25_r8*(pn(i-1,j-1)+pn(i-1,j)+                      &
     &                      pn(i  ,j-1)+pn(i  ,j))
              cff1=MIN(dZdx_p(i,j,k1),0.0_r8)
              cff2=MAX(dZdx_p(i,j,k1),0.0_r8)
              cff3=MIN(dZde_p(i,j,k1),0.0_r8)
              cff4=MAX(dZde_p(i,j,k1),0.0_r8)
              tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i,j,k1)))*            &
     &                tl_dZdx_p(i,j,k1)
              tl_cff2=(0.5_r8+SIGN(0.5_r8, dZdx_p(i,j,k1)))*            &
     &                tl_dZdx_p(i,j,k1)
              tl_cff3=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j,k1)))*            &
     &                tl_dZde_p(i,j,k1)
              tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j,k1)))*            &
     &                tl_dZde_p(i,j,k1)
#ifdef VISC_3DCOEF
              cff=0.25_r8*                                              &
     &            (Hz(i-1,j  ,k)+Hz(i,j  ,k)+                           &
     &             Hz(i-1,j-1,k)+Hz(i,j-1,k))*                          &
     &             (on_p(i,j)*(dnVdx(i,j,k1)-                           &
     &                         0.5_r8*pn_p*                             &
     &                         (cff1*(dVdz(i-1,j,k1)+                   &
     &                                dVdz(i  ,j,k2))+                  &
     &                          cff2*(dVdz(i-1,j,k2)+                   &
     &                                dVdz(i  ,j,k1))))+                &
     &              om_p(i,j)*(dmUde(i,j,k1)-                           &
     &                         0.5_r8*pm_p*                             &
     &                         (cff3*(dUdz(i,j-1,k1)+                   &
     &                                dUdz(i,j  ,k2))+                  &
     &                          cff4*(dUdz(i,j-1,k2)+                   &
     &                                dUdz(i,j  ,k1)))))
#else
!>            cff=0.25_r8*                                              &
!>   &            (Hz(i-1,j  ,k)+Hz(i,j  ,k)+                           &
!>   &             Hz(i-1,j-1,k)+Hz(i,j-1,k))*                          &
!>   &             (on_p(i,j)*(dnVdx(i,j,k1)-                           &
!>   &                         0.5_r8*pn_p*                             &
!>   &                         (cff1*(dVdz(i-1,j,k1)+                   &
!>   &                                dVdz(i  ,j,k2))+                  &
!>   &                          cff2*(dVdz(i-1,j,k2)+                   &
!>   &                                dVdz(i  ,j,k1))))+                &
!>   &              om_p(i,j)*(dmUde(i,j,k1)-                           &
!>   &                         0.5_r8*pm_p*                             &
!>   &                         (cff3*(dUdz(i,j-1,k1)+                   &
!>   &                                dUdz(i,j  ,k2))+                  &
!>   &                          cff4*(dUdz(i,j-1,k2)+                   &
!>   &                                dUdz(i,j  ,k1)))))
!>
#endif
              tl_cff=0.25_r8*                                           &
     &               ((tl_Hz(i-1,j  ,k)+tl_Hz(i,j  ,k)+                 &
     &                 tl_Hz(i-1,j-1,k)+tl_Hz(i,j-1,k))*                &
     &                 (on_p(i,j)*(dnVdx(i,j,k1)-                       &
     &                             0.5_r8*pn_p*                         &
     &                             (cff1*(dVdz(i-1,j,k1)+               &
     &                                    dVdz(i  ,j,k2))+              &
     &                              cff2*(dVdz(i-1,j,k2)+               &
     &                                    dVdz(i  ,j,k1))))+            &
     &                  om_p(i,j)*(dmUde(i,j,k1)-                       &
     &                             0.5_r8*pm_p*                         &
     &                             (cff3*(dUdz(i,j-1,k1)+               &
     &                                    dUdz(i,j  ,k2))+              &
     &                              cff4*(dUdz(i,j-1,k2)+               &
     &                                    dUdz(i,j  ,k1)))))+           &
     &                (Hz(i-1,j  ,k)+Hz(i,j  ,k)+                       &
     &                 Hz(i-1,j-1,k)+Hz(i,j-1,k))*                      &
     &                 (on_p(i,j)*(tl_dnVdx(i,j,k1)-                    &
     &                             0.5_r8*pn_p*                         &
     &                             (tl_cff1*(dVdz(i-1,j,k1)+            &
     &                                       dVdz(i  ,j,k2))+           &
     &                              cff1*(tl_dVdz(i-1,j,k1)+            &
     &                                    tl_dVdz(i  ,j,k2))+           &
     &                              tl_cff2*(dVdz(i-1,j,k2)+            &
     &                                       dVdz(i  ,j,k1))+           &
     &                              cff2*(tl_dVdz(i-1,j,k2)+            &
     &                                    tl_dVdz(i  ,j,k1))))+         &
     &                  om_p(i,j)*(tl_dmUde(i,j,k1)-                    &
     &                             0.5_r8*pm_p*                         &
     &                             (tl_cff3*(dUdz(i,j-1,k1)+            &
     &                                       dUdz(i,j  ,k2))+           &
     &                              cff3*(tl_dUdz(i,j-1,k1)+            &
     &                                    tl_dUdz(i,j  ,k2))+           &
     &                              tl_cff4*(dUdz(i,j-1,k2)+            &
     &                                       dUdz(i,j  ,k1))+           &
     &                              cff4*(tl_dUdz(i,j-1,k2)+            &
     &                                    tl_dUdz(i,j  ,k1))))))
#ifdef MASKING
# ifdef VISC_3DCOEF
              cff=cff*pmask(i,j)
# else
!>            cff=cff*pmask(i,j)
!>
# endif
              tl_cff=tl_cff*pmask(i,j)
#endif
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
              Uvis_p=0.25_r8*                                           &
     &               (Uvis3d_r(i-1,j-1,k)+Uvis3d_r(i-1,j,k)+            &
     &                Uvis3d_r(i  ,j-1,k)+Uvis3d_r(i  ,j,k))
              tl_Uvis_p=0.25_r8*                                        &
     &                  (tl_Uvis3d_r(i-1,j-1,k)+tl_Uvis3d_r(i-1,j,k)+   &
     &                   tl_Uvis3d_r(i  ,j-1,k)+tl_Uvis3d_r(i  ,j,k))
              Vvis_p=0.25_r8*                                           &
     &               (Vvis3d_r(i-1,j-1,k)+Vvis3d_r(i-1,j,k)+            &
     &                Vvis3d_r(i  ,j-1,k)+Vvis3d_r(i  ,j,k))
              tl_Vvis_p=0.25_r8*                                        &
     &                  (tl_Vvis3d_r(i-1,j-1,k)+tl_Vvis3d_r(i-1,j,k)+   &
     &                   tl_Vvis3d_r(i  ,j-1,k)+tl_Vvis3d_r(i  ,j,k))
!>            UFe(i,j)=om_p(i,j)*om_p(i,j)*Uvis_p*cff
!>
              tl_UFe(i,j)=om_p(i,j)*om_p(i,j)*                          &
     &                    (tl_Uvis_p*cff+Uvis_p*tl_cff)
!>            VFx(i,j)=on_p(i,j)*on_p(i,j)*Vvis_p*cff
!>
              tl_VFx(i,j)=on_p(i,j)*on_p(i,j)*                          &
     &                    (tl_Vvis_p*cff+Vvis_p*tl_cff)
# else
              visc_p=0.25_r8*                                           &
     &               (visc3d_r(i-1,j-1,k)+visc3d_r(i-1,j,k)+            &
     &                visc3d_r(i  ,j-1,k)+visc3d_r(i  ,j,k))
              tl_visc_p=0.25_r8*                                        &
     &                  (tl_visc3d_r(i-1,j-1,k)+tl_visc3d_r(i-1,j,k)+   &
     &                   tl_visc3d_r(i  ,j-1,k)+tl_visc3d_r(i  ,j,k))
!>            UFe(i,j)=om_p(i,j)*om_p(i,j)*visc_p*cff
!>
              tl_UFe(i,j)=om_p(i,j)*om_p(i,j)*                          &
     &                    (tl_visc_p*cff+visc_p*tl_cff)
!>            VFx(i,j)=on_p(i,j)*on_p(i,j)*visc_p*cff
!>
              tl_VFx(i,j)=on_p(i,j)*on_p(i,j)*                          &
     &                    (tl_visc_p*cff+visc_p*tl_cff)
# endif
#else
!>            UFe(i,j)=om_p(i,j)*om_p(i,j)*visc4_p(i,j)*cff
!>
              tl_UFe(i,j)=om_p(i,j)*om_p(i,j)*visc4_p(i,j)*tl_cff
!>            VFx(i,j)=on_p(i,j)*on_p(i,j)*visc4_p(i,j)*cff
!>
              tl_VFx(i,j)=on_p(i,j)*on_p(i,j)*visc4_p(i,j)*tl_cff
#endif
            END DO
          END DO
!
!  Compute vertical flux (m2/s2) due to sloping terrain-following
!  surfaces.
!
          IF (k.lt.N(ng)) THEN
            DO j=Jstr,Jend
              DO i=IstrU,Iend
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
                cff=0.125_r8*                                           &
     &              (Uvis3d_r(i-1,j,k  )+Uvis3d_r(i,j,k  )+             &
     &               Uvis3d_r(i-1,j,k+1)+Uvis3d_r(i,j,k+1))
                tl_cff=0.125_r8*                                        &
     &                 (tl_Uvis3d_r(i-1,j,k  )+tl_Uvis3d_r(i,j,k  )+    &
     &                  tl_Uvis3d_r(i-1,j,k+1)+tl_Uvis3d_r(i,j,k+1))
# else
                cff=0.125_r8*                                           &
     &              (visc3d_r(i-1,j,k  )+visc3d_r(i,j,k  )+             &
     &               visc3d_r(i-1,j,k+1)+visc3d_r(i,j,k+1))
                tl_cff=0.125_r8*                                        &
     &                 (tl_visc3d_r(i-1,j,k  )+tl_visc3d_r(i,j,k  )+    &
     &                  tl_visc3d_r(i-1,j,k+1)+tl_visc3d_r(i,j,k+1))
# endif
                fac1=cff*on_u(i,j)
                tl_fac1=tl_cff*on_u(i,j)
                fac2=cff*om_u(i,j)
                tl_fac2=tl_cff*om_u(i,j)
#else
                cff=0.25_r8*(visc4_r(i-1,j)+visc4_r(i,j))
                fac1=cff*on_u(i,j)
                fac2=cff*om_u(i,j)
#endif
                cff=0.5_r8*(pn(i-1,j)+pn(i,j))
                dnUdz=cff*dUdz(i,j,k2)
                tl_dnUdz=cff*tl_dUdz(i,j,k2)
                dnVdz=cff*0.25_r8*(dVdz(i-1,j+1,k2)+                    &
     &                             dVdz(i  ,j+1,k2)+                    &
     &                             dVdz(i-1,j  ,k2)+                    &
     &                             dVdz(i  ,j  ,k2))
                tl_dnVdz=cff*0.25_r8*(tl_dVdz(i-1,j+1,k2)+              &
     &                                tl_dVdz(i  ,j+1,k2)+              &
     &                                tl_dVdz(i-1,j  ,k2)+              &
     &                                tl_dVdz(i  ,j  ,k2))
                cff=0.5_r8*(pm(i-1,j)+pm(i,j))
                dmUdz=cff*dUdz(i,j,k2)
                tl_dmUdz=cff*tl_dUdz(i,j,k2)
                dmVdz=cff*0.25_r8*(dVdz(i-1,j+1,k2)+                    &
     &                             dVdz(i  ,j+1,k2)+                    &
     &                             dVdz(i-1,j  ,k2)+                    &
     &                             dVdz(i  ,j  ,k2))
                tl_dmVdz=cff*0.25_r8*(tl_dVdz(i-1,j+1,k2)+              &
     &                                tl_dVdz(i  ,j+1,k2)+              &
     &                                tl_dVdz(i-1,j  ,k2)+              &
     &                                tl_dVdz(i  ,j  ,k2))

                cff1=MIN(dZdx_r(i-1,j,k1),0.0_r8)
                cff2=MIN(dZdx_r(i  ,j,k2),0.0_r8)
                cff3=MAX(dZdx_r(i-1,j,k2),0.0_r8)
                cff4=MAX(dZdx_r(i  ,j,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i-1,j,k1)))*        &
     &                  tl_dZdx_r(i-1,j,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i  ,j,k2)))*        &
     &                  tl_dZdx_r(i  ,j,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZdx_r(i-1,j,k2)))*        &
     &                  tl_dZdx_r(i-1,j,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZdx_r(i  ,j,k1)))*        &
                        tl_dZdx_r(i  ,j,k1)
!>              UFsx(i,j,k2)=fac1*                                      &
!>   &                       (cff1*(cff1*dnUdz-dnUdx(i-1,j,k1))+        &
!>   &                        cff2*(cff2*dnUdz-dnUdx(i  ,j,k2))+        &
!>   &                        cff3*(cff3*dnUdz-dnUdx(i-1,j,k2))+        &
!>   &                        cff4*(cff4*dnUdz-dnUdx(i  ,j,k1)))
!>
                tl_UFsx(i,j,k2)=fac1*                                   &
     &                          (tl_cff1*(cff1*dnUdz-dnUdx(i-1,j,k1))+  &
     &                           tl_cff2*(cff2*dnUdz-dnUdx(i  ,j,k2))+  &
     &                           tl_cff3*(cff3*dnUdz-dnUdx(i-1,j,k2))+  &
     &                           tl_cff4*(cff4*dnUdz-dnUdx(i  ,j,k1))+  &
     &                           cff1*(tl_cff1*dnUdz+cff1*tl_dnUdz-     &
     &                                 tl_dnUdx(i-1,j,k1))+             &
     &                           cff2*(tl_cff2*dnUdz+cff2*tl_dnUdz-     &
     &                                 tl_dnUdx(i  ,j,k2))+             &
     &                           cff3*(tl_cff3*dnUdz+cff3*tl_dnUdz-     &
     &                                 tl_dnUdx(i-1,j,k2))+             &
     &                           cff4*(tl_cff4*dnUdz+cff4*tl_dnUdz-     &
     &                                 tl_dnUdx(i  ,j,k1)))
#ifdef VISC_3DCOEF
                tl_UFsx(i,j,k2)=tl_UFsx(i,j,k2)+                        &
     &                          tl_fac1*                                &
     &                          (cff1*(cff1*dnUdz-dnUdx(i-1,j,k1))+     &
     &                           cff2*(cff2*dnUdz-dnUdx(i  ,j,k2))+     &
     &                           cff3*(cff3*dnUdz-dnUdx(i-1,j,k2))+     &
     &                           cff4*(cff4*dnUdz-dnUdx(i  ,j,k1)))
#endif

                cff1=MIN(dZde_p(i,j  ,k1),0.0_r8)
                cff2=MIN(dZde_p(i,j+1,k2),0.0_r8)
                cff3=MAX(dZde_p(i,j  ,k2),0.0_r8)
                cff4=MAX(dZde_p(i,j+1,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j  ,k1)))*        &
     &                  tl_dZde_p(i,j  ,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j+1,k2)))*        &
     &                  tl_dZde_p(i,j+1,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j  ,k2)))*        &
     &                  tl_dZde_p(i,j  ,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j+1,k1)))*        &
                        tl_dZde_p(i,j+1,k1)
!>              UFse(i,j,k2)=fac2*                                      &
!>   &                       (cff1*(cff1*dmUdz-dmUde(i,j  ,k1))+        &
!>   &                        cff2*(cff2*dmUdz-dmUde(i,j+1,k2))+        &
!>   &                        cff3*(cff3*dmUdz-dmUde(i,j  ,k2))+        &
!>   &                        cff4*(cff4*dmUdz-dmUde(i,j+1,k1)))
!>
                tl_UFse(i,j,k2)=fac2*                                   &
     &                          (tl_cff1*(cff1*dmUdz-dmUde(i,j  ,k1))+  &
     &                           tl_cff2*(cff2*dmUdz-dmUde(i,j+1,k2))+  &
     &                           tl_cff3*(cff3*dmUdz-dmUde(i,j  ,k2))+  &
     &                           tl_cff4*(cff4*dmUdz-dmUde(i,j+1,k1))+  &
     &                           cff1*(tl_cff1*dmUdz+cff1*tl_dmUdz-     &
     &                                 tl_dmUde(i,j  ,k1))+             &
     &                           cff2*(tl_cff2*dmUdz+cff2*tl_dmUdz-     &
     &                                 tl_dmUde(i,j+1,k2))+             &
     &                           cff3*(tl_cff3*dmUdz+cff3*tl_dmUdz-     &
     &                                 tl_dmUde(i,j  ,k2))+             &
     &                           cff4*(tl_cff4*dmUdz+cff4*tl_dmUdz-     &
     &                                 tl_dmUde(i,j+1,k1)))
#ifdef VISC_3DCOEF
                tl_UFse(i,j,k2)=tl_UFse(i,j,k2)+                        &
     &                          tl_fac2*                                &
     &                          (cff1*(cff1*dmUdz-dmUde(i,j  ,k1))+     &
     &                           cff2*(cff2*dmUdz-dmUde(i,j+1,k2))+     &
     &                           cff3*(cff3*dmUdz-dmUde(i,j  ,k2))+     &
     &                           cff4*(cff4*dmUdz-dmUde(i,j+1,k1)))
#endif

                cff1=MIN(dZde_p(i,j  ,k1),0.0_r8)
                cff2=MIN(dZde_p(i,j+1,k2),0.0_r8)
                cff3=MAX(dZde_p(i,j  ,k2),0.0_r8)
                cff4=MAX(dZde_p(i,j+1,k1),0.0_r8)
                cff5=MIN(dZdx_p(i,j  ,k1),0.0_r8)
                cff6=MIN(dZdx_p(i,j+1,k2),0.0_r8)
                cff7=MAX(dZdx_p(i,j  ,k2),0.0_r8)
                cff8=MAX(dZdx_p(i,j+1,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j  ,k1)))*        &
     &                  tl_dZde_p(i,j  ,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZde_p(i,j+1,k2)))*        &
     &                  tl_dZde_p(i,j+1,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j  ,k2)))*        &
     &                  tl_dZde_p(i,j  ,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_p(i,j+1,k1)))*        &
     &                  tl_dZde_p(i,j+1,k1)
                tl_cff5=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i,j  ,k1)))*        &
     &                  tl_dZdx_p(i,j  ,k1)
                tl_cff6=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i,j+1,k2)))*        &
     &                  tl_dZdx_p(i,j+1,k2)
                tl_cff7=(0.5_r8+SIGN(0.5_r8, dZdx_p(i,j  ,k2)))*        &
     &                  tl_dZdx_p(i,j  ,k2)
                tl_cff8=(0.5_r8+SIGN(0.5_r8, dZdx_p(i,j+1,k1)))*        &
     &                  tl_dZdx_p(i,j+1,k1)
!>              UFsx(i,j,k2)=UFsx(i,j,k2)+                              &
!>   &                       fac1*                                      &
!>   &                       (cff1*(cff5*dnVdz-dnVdx(i,j  ,k1))+        &
!>   &                        cff2*(cff6*dnVdz-dnVdx(i,j+1,k2))+        &
!>   &                        cff3*(cff7*dnVdz-dnVdx(i,j  ,k2))+        &
!>   &                        cff4*(cff8*dnVdz-dnVdx(i,j+1,k1)))
!>
                tl_UFsx(i,j,k2)=tl_UFsx(i,j,k2)+                        &
     &                          fac1*                                   &
     &                          (tl_cff1*(cff5*dnVdz-dnVdx(i,j  ,k1))+  &
     &                           tl_cff2*(cff6*dnVdz-dnVdx(i,j+1,k2))+  &
     &                           tl_cff3*(cff7*dnVdz-dnVdx(i,j  ,k2))+  &
     &                           tl_cff4*(cff8*dnVdz-dnVdx(i,j+1,k1))+  &
     &                           cff1*(tl_cff5*dnVdz+cff5*tl_dnVdz-     &
     &                                 tl_dnVdx(i,j  ,k1))+             &
     &                           cff2*(tl_cff6*dnVdz+cff6*tl_dnVdz-     &
     &                                 tl_dnVdx(i,j+1,k2))+             &
     &                           cff3*(tl_cff7*dnVdz+cff7*tl_dnVdz-     &
     &                                 tl_dnVdx(i,j  ,k2))+             &
     &                           cff4*(tl_cff8*dnVdz+cff8*tl_dnVdz-     &
     &                                 tl_dnVdx(i,j+1,k1)))
#ifdef VISC_3DCOEF
                tl_UFsx(i,j,k2)=tl_UFsx(i,j,k2)+                        &
     &                          tl_fac1*                                &
     &                          (cff1*(cff5*dnVdz-dnVdx(i,j  ,k1))+     &
     &                           cff2*(cff6*dnVdz-dnVdx(i,j+1,k2))+     &
     &                           cff3*(cff7*dnVdz-dnVdx(i,j  ,k2))+     &
     &                           cff4*(cff8*dnVdz-dnVdx(i,j+1,k1)))
#endif

                cff1=MIN(dZdx_r(i-1,j,k1),0.0_r8)
                cff2=MIN(dZdx_r(i  ,j,k2),0.0_r8)
                cff3=MAX(dZdx_r(i-1,j,k2),0.0_r8)
                cff4=MAX(dZdx_r(i  ,j,k1),0.0_r8)
                cff5=MIN(dZde_r(i-1,j,k1),0.0_r8)
                cff6=MIN(dZde_r(i  ,j,k2),0.0_r8)
                cff7=MAX(dZde_r(i-1,j,k2),0.0_r8)
                cff8=MAX(dZde_r(i  ,j,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i-1,j,k1)))*        &
     &                  tl_dZdx_r(i-1,j,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i  ,j,k2)))*        &
     &                  tl_dZdx_r(i  ,j,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZdx_r(i-1,j,k2)))*        &
     &                  tl_dZdx_r(i-1,j,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZdx_r(i  ,j,k1)))*        &
     &                  tl_dZdx_r(i  ,j,k1)
                tl_cff5=(0.5_r8+SIGN(0.5_r8,-dZde_r(i-1,j,k1)))*        &
     &                  tl_dZde_r(i-1,j,k1)
                tl_cff6=(0.5_r8+SIGN(0.5_r8,-dZde_r(i  ,j,k2)))*        &
     &                  tl_dZde_r(i  ,j,k2)
                tl_cff7=(0.5_r8+SIGN(0.5_r8, dZde_r(i-1,j,k2)))*        &
     &                  tl_dZde_r(i-1,j,k2)
                tl_cff8=(0.5_r8+SIGN(0.5_r8, dZde_r(i  ,j,k1)))*        &
     &                  tl_dZde_r(i  ,j,k1)
!>              UFse(i,j,k2)=UFse(i,j,k2)-                              &
!>   &                       fac2*                                      &
!>   &                       (cff1*(cff5*dmVdz-dmVde(i-1,j,k1))+        &
!>   &                        cff2*(cff6*dmVdz-dmVde(i  ,j,k2))+        &
!>   &                        cff3*(cff7*dmVdz-dmVde(i-1,j,k2))+        &
!>   &                        cff4*(cff8*dmVdz-dmVde(i  ,j,k1)))
!>
                tl_UFse(i,j,k2)=tl_UFse(i,j,k2)-                        &
     &                          fac2*                                   &
     &                          (tl_cff1*(cff5*dmVdz-dmVde(i-1,j,k1))+  &
     &                           tl_cff2*(cff6*dmVdz-dmVde(i  ,j,k2))+  &
     &                           tl_cff3*(cff7*dmVdz-dmVde(i-1,j,k2))+  &
     &                           tl_cff4*(cff8*dmVdz-dmVde(i  ,j,k1))+  &
     &                           cff1*(tl_cff5*dmVdz+cff5*tl_dmVdz-     &
     &                                 tl_dmVde(i-1,j,k1))+             &
     &                           cff2*(tl_cff6*dmVdz+cff6*tl_dmVdz-     &
     &                                 tl_dmVde(i  ,j,k2))+             &
     &                           cff3*(tl_cff7*dmVdz+cff7*tl_dmVdz-     &
     &                                 tl_dmVde(i-1,j,k2))+             &
     &                           cff4*(tl_cff8*dmVdz+cff8*tl_dmVdz-     &
     &                                 tl_dmVde(i  ,j,k1)))
#ifdef VISC_3DCOEF
                tl_UFse(i,j,k2)=tl_UFse(i,j,k2)-                        &
     &                          tl_fac2*                                &
     &                          (cff1*(cff5*dmVdz-dmVde(i-1,j,k1))+     &
     &                           cff2*(cff6*dmVdz-dmVde(i  ,j,k2))+     &
     &                           cff3*(cff7*dmVdz-dmVde(i-1,j,k2))+     &
     &                           cff4*(cff8*dmVdz-dmVde(i  ,j,k1)))
#endif
              END DO
            END DO
!
            DO j=JstrV,Jend
              DO i=Istr,Iend
#ifdef VISC_3DCOEF
# ifdef UV_U3ADV_SPLIT
                cff=0.125_r8*                                           &
     &              (Vvis3d_r(i,j-1,k  )+Vvis3d_r(i,j,k  )+             &
     &               Vvis3d_r(i,j-1,k+1)+Vvis3d_r(i,j,k+1))
                tl_cff=0.125_r8*                                        &
     &                 (tl_Vvis3d_r(i,j-1,k  )+tl_Vvis3d_r(i,j,k  )+    &
     &                  tl_Vvis3d_r(i,j-1,k+1)+tl_Vvis3d_r(i,j,k+1))
# else
                cff=0.125_r8*                                           &
     &              (visc3d_r(i,j-1,k  )+visc3d_r(i,j,k  )+             &
     &               visc3d_r(i,j-1,k+1)+visc3d_r(i,j,k+1))
                tl_cff=0.125_r8*                                        &
     &                 (tl_visc3d_r(i,j-1,k  )+tl_visc3d_r(i,j,k  )+    &
     &                  tl_visc3d_r(i,j-1,k+1)+tl_visc3d_r(i,j,k+1))
# endif
                fac1=cff*on_v(i,j)
                tl_fac1=tl_cff*on_v(i,j)
                fac2=cff*om_v(i,j)
                tl_fac2=tl_cff*om_v(i,j)
#else
                cff=0.25_r8*(visc4_r(i,j-1)+visc4_r(i,j))
                fac1=cff*on_v(i,j)
                fac2=cff*om_v(i,j)
#endif
                cff=0.5_r8*(pn(i,j-1)+pn(i,j))
                dnUdz=cff*0.25_r8*(dUdz(i  ,j  ,k2)+                    &
     &                             dUdz(i+1,j  ,k2)+                    &
     &                             dUdz(i  ,j-1,k2)+                    &
     &                             dUdz(i+1,j-1,k2))
                tl_dnUdz=cff*0.25_r8*(tl_dUdz(i  ,j  ,k2)+              &
     &                                tl_dUdz(i+1,j  ,k2)+              &
     &                                tl_dUdz(i  ,j-1,k2)+              &
     &                                tl_dUdz(i+1,j-1,k2))
                dnVdz=cff*dVdz(i,j,k2)
                tl_dnVdz=cff*tl_dVdz(i,j,k2)
                cff=0.5_r8*(pm(i,j-1)+pm(i,j))
                dmUdz=cff*0.25_r8*(dUdz(i  ,j  ,k2)+                    &
     &                             dUdz(i+1,j  ,k2)+                    &
     &                             dUdz(i  ,j-1,k2)+                    &
     &                             dUdz(i+1,j-1,k2))
                tl_dmUdz=cff*0.25_r8*(tl_dUdz(i  ,j  ,k2)+              &
     &                                tl_dUdz(i+1,j  ,k2)+              &
     &                                tl_dUdz(i  ,j-1,k2)+              &
     &                                tl_dUdz(i+1,j-1,k2))
                dmVdz=cff*dVdz(i,j,k2)
                tl_dmVdz=cff*tl_dVdz(i,j,k2)

                cff1=MIN(dZdx_p(i  ,j,k1),0.0_r8)
                cff2=MIN(dZdx_p(i+1,j,k2),0.0_r8)
                cff3=MAX(dZdx_p(i  ,j,k2),0.0_r8)
                cff4=MAX(dZdx_p(i+1,j,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i  ,j,k1)))*        &
     &                  tl_dZdx_p(i  ,j,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i+1,j,k2)))*        &
     &                  tl_dZdx_p(i+1,j,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZdx_p(i  ,j,k2)))*        &
     &                  tl_dZdx_p(i  ,j,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZdx_p(i+1,j,k1)))*        &
     &                  tl_dZdx_p(i+1,j,k1)
!>              VFsx(i,j,k2)=fac1*                                      &
!>   &                       (cff1*(cff1*dnVdz-dnVdx(i  ,j,k1))+        &
!>   &                        cff2*(cff2*dnVdz-dnVdx(i+1,j,k2))+        &
!>   &                        cff3*(cff3*dnVdz-dnVdx(i  ,j,k2))+        &
!>   &                        cff4*(cff4*dnVdz-dnVdx(i+1,j,k1)))
!>
                tl_VFsx(i,j,k2)=fac1*                                   &
     &                          (tl_cff1*(cff1*dnVdz-dnVdx(i  ,j,k1))+  &
     &                           tl_cff2*(cff2*dnVdz-dnVdx(i+1,j,k2))+  &
     &                           tl_cff3*(cff3*dnVdz-dnVdx(i  ,j,k2))+  &
     &                           tl_cff4*(cff4*dnVdz-dnVdx(i+1,j,k1))+  &
     &                           cff1*(tl_cff1*dnVdz+cff1*tl_dnVdz-     &
     &                                 tl_dnVdx(i  ,j,k1))+             &
     &                           cff2*(tl_cff2*dnVdz+cff2*tl_dnVdz-     &
     &                                 tl_dnVdx(i+1,j,k2))+             &
     &                           cff3*(tl_cff3*dnVdz+cff3*tl_dnVdz-     &
     &                                 tl_dnVdx(i  ,j,k2))+             &
     &                           cff4*(tl_cff4*dnVdz+cff4*tl_dnVdz-     &
     &                                 tl_dnVdx(i+1,j,k1)))
#ifdef VISC_3DCOEF
                tl_VFsx(i,j,k2)=tl_VFsx(i,j,k2)+                        &
     &                          tl_fac1*                                &
     &                          (cff1*(cff1*dnVdz-dnVdx(i  ,j,k1))+     &
     &                           cff2*(cff2*dnVdz-dnVdx(i+1,j,k2))+     &
     &                           cff3*(cff3*dnVdz-dnVdx(i  ,j,k2))+     &
     &                           cff4*(cff4*dnVdz-dnVdx(i+1,j,k1)))
#endif

                cff1=MIN(dZde_r(i,j-1,k1),0.0_r8)
                cff2=MIN(dZde_r(i,j  ,k2),0.0_r8)
                cff3=MAX(dZde_r(i,j-1,k2),0.0_r8)
                cff4=MAX(dZde_r(i,j  ,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j-1,k1)))*        &
     &                  tl_dZde_r(i,j-1,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j  ,k2)))*        &
     &                  tl_dZde_r(i,j  ,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j-1,k2)))*        &
     &                  tl_dZde_r(i,j-1,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j  ,k1)))*        &
     &                  tl_dZde_r(i,j  ,k1)
!>              VFse(i,j,k2)=fac2*                                      &
!>   &                       (cff1*(cff1*dmVdz-dmVde(i,j-1,k1))+        &
!>   &                        cff2*(cff2*dmVdz-dmVde(i,j  ,k2))+        &
!>   &                        cff3*(cff3*dmVdz-dmVde(i,j-1,k2))+        &
!>   &                        cff4*(cff4*dmVdz-dmVde(i,j  ,k1)))
!>
                tl_VFse(i,j,k2)=fac2*                                   &
     &                          (tl_cff1*(cff1*dmVdz-dmVde(i,j-1,k1))+  &
     &                           tl_cff2*(cff2*dmVdz-dmVde(i,j  ,k2))+  &
     &                           tl_cff3*(cff3*dmVdz-dmVde(i,j-1,k2))+  &
     &                           tl_cff4*(cff4*dmVdz-dmVde(i,j  ,k1))+  &
     &                           cff1*(tl_cff1*dmVdz+cff1*tl_dmVdz-     &
     &                                 tl_dmVde(i,j-1,k1))+             &
     &                           cff2*(tl_cff2*dmVdz+cff2*tl_dmVdz-     &
     &                                 tl_dmVde(i,j  ,k2))+             &
     &                           cff3*(tl_cff3*dmVdz+cff3*tl_dmVdz-     &
     &                                 tl_dmVde(i,j-1,k2))+             &
     &                           cff4*(tl_cff4*dmVdz+cff4*tl_dmVdz-     &
     &                                 tl_dmVde(i,j  ,k1)))
#ifdef VISC_3DCOEF
                tl_VFse(i,j,k2)=tl_VFse(i,j,k2)+                        &
     &                          tl_fac2*                                &
     &                          (cff1*(cff1*dmVdz-dmVde(i,j-1,k1))+     &
     &                           cff2*(cff2*dmVdz-dmVde(i,j  ,k2))+     &
     &                           cff3*(cff3*dmVdz-dmVde(i,j-1,k2))+     &
     &                           cff4*(cff4*dmVdz-dmVde(i,j  ,k1)))
#endif

                cff1=MIN(dZde_r(i,j-1,k1),0.0_r8)
                cff2=MIN(dZde_r(i,j  ,k2),0.0_r8)
                cff3=MAX(dZde_r(i,j-1,k2),0.0_r8)
                cff4=MAX(dZde_r(i,j  ,k1),0.0_r8)
                cff5=MIN(dZdx_r(i,j-1,k1),0.0_r8)
                cff6=MIN(dZdx_r(i,j  ,k2),0.0_r8)
                cff7=MAX(dZdx_r(i,j-1,k2),0.0_r8)
                cff8=MAX(dZdx_r(i,j  ,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j-1,k1)))*        &
     &                  tl_dZde_r(i,j-1,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZde_r(i,j  ,k2)))*        &
     &                  tl_dZde_r(i,j  ,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j-1,k2)))*        &
     &                  tl_dZde_r(i,j-1,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZde_r(i,j  ,k1)))*        &
     &                  tl_dZde_r(i,j  ,k1)
                tl_cff5=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i,j-1,k1)))*        &
     &                  tl_dZdx_r(i,j-1,k1)
                tl_cff6=(0.5_r8+SIGN(0.5_r8,-dZdx_r(i,j  ,k2)))*        &
     &                  tl_dZdx_r(i,j  ,k2)
                tl_cff7=(0.5_r8+SIGN(0.5_r8, dZdx_r(i,j-1,k2)))*        &
     &                  tl_dZdx_r(i,j-1,k2)
                tl_cff8=(0.5_r8+SIGN(0.5_r8, dZdx_r(i,j  ,k1)))*        &
     &                  tl_dZdx_r(i,j  ,k1)
!>              VFsx(i,j,k2)=VFsx(i,j,k2)-                              &
!>   &                       fac1*                                      &
!>   &                       (cff1*(cff5*dnUdz-dnUdx(i,j-1,k1))+        &
!>   &                        cff2*(cff6*dnUdz-dnUdx(i,j  ,k2))+        &
!>   &                        cff3*(cff7*dnUdz-dnUdx(i,j-1,k2))+        &
!>   &                        cff4*(cff8*dnUdz-dnUdx(i,j  ,k1)))
!>
                tl_VFsx(i,j,k2)=tl_VFsx(i,j,k2)-                        &
     &                          fac1*                                   &
     &                          (tl_cff1*(cff5*dnUdz-dnUdx(i,j-1,k1))+  &
     &                           tl_cff2*(cff6*dnUdz-dnUdx(i,j  ,k2))+  &
     &                           tl_cff3*(cff7*dnUdz-dnUdx(i,j-1,k2))+  &
     &                           tl_cff4*(cff8*dnUdz-dnUdx(i,j  ,k1))+  &
     &                           cff1*(tl_cff5*dnUdz+cff5*tl_dnUdz-     &
     &                                 tl_dnUdx(i,j-1,k1))+             &
     &                           cff2*(tl_cff6*dnUdz+cff6*tl_dnUdz-     &
     &                                 tl_dnUdx(i,j  ,k2))+             &
     &                           cff3*(tl_cff7*dnUdz+cff7*tl_dnUdz-     &
     &                                 tl_dnUdx(i,j-1,k2))+             &
     &                           cff4*(tl_cff8*dnUdz+cff8*tl_dnUdz-     &
     &                                 tl_dnUdx(i,j  ,k1)))
#ifdef VISC_3DCOEF
                tl_VFsx(i,j,k2)=tl_VFsx(i,j,k2)-                        &
     &                          tl_fac1*                                &
     &                          (cff1*(cff5*dnUdz-dnUdx(i,j-1,k1))+     &
     &                           cff2*(cff6*dnUdz-dnUdx(i,j  ,k2))+     &
     &                           cff3*(cff7*dnUdz-dnUdx(i,j-1,k2))+     &
     &                           cff4*(cff8*dnUdz-dnUdx(i,j  ,k1)))
#endif

                cff1=MIN(dZdx_p(i  ,j,k1),0.0_r8)
                cff2=MIN(dZdx_p(i+1,j,k2),0.0_r8)
                cff3=MAX(dZdx_p(i  ,j,k2),0.0_r8)
                cff4=MAX(dZdx_p(i+1,j,k1),0.0_r8)
                cff5=MIN(dZde_p(i  ,j,k1),0.0_r8)
                cff6=MIN(dZde_p(i+1,j,k2),0.0_r8)
                cff7=MAX(dZde_p(i  ,j,k2),0.0_r8)
                cff8=MAX(dZde_p(i+1,j,k1),0.0_r8)
                tl_cff1=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i  ,j,k1)))*        &
     &                  tl_dZdx_p(i  ,j,k1)
                tl_cff2=(0.5_r8+SIGN(0.5_r8,-dZdx_p(i+1,j,k2)))*        &
     &                  tl_dZdx_p(i+1,j,k2)
                tl_cff3=(0.5_r8+SIGN(0.5_r8, dZdx_p(i  ,j,k2)))*        &
     &                  tl_dZdx_p(i  ,j,k2)
                tl_cff4=(0.5_r8+SIGN(0.5_r8, dZdx_p(i+1,j,k1)))*        &
     &                  tl_dZdx_p(i+1,j,k1)
                tl_cff5=(0.5_r8+SIGN(0.5_r8,-dZde_p(i  ,j,k1)))*        &
     &                  tl_dZde_p(i  ,j,k1)
                tl_cff6=(0.5_r8+SIGN(0.5_r8,-dZde_p(i+1,j,k2)))*        &
     &                  tl_dZde_p(i+1,j,k2)
                tl_cff7=(0.5_r8+SIGN(0.5_r8, dZde_p(i  ,j,k2)))*        &
     &                  tl_dZde_p(i  ,j,k2)
                tl_cff8=(0.5_r8+SIGN(0.5_r8, dZde_p(i+1,j,k1)))*        &
     &                  tl_dZde_p(i+1,j,k1)
!>              VFse(i,j,k2)=VFse(i,j,k2)+                              &
!>   &                       fac2*                                      &
!>   &                       (cff1*(cff5*dmUdz-dmUde(i  ,j,k1))+        &
!>   &                        cff2*(cff6*dmUdz-dmUde(i+1,j,k2))+        &
!>   &                        cff3*(cff7*dmUdz-dmUde(i  ,j,k2))+        &
!>   &                        cff4*(cff8*dmUdz-dmUde(i+1,j,k1)))
!>
                tl_VFse(i,j,k2)=tl_VFse(i,j,k2)+                        &
     &                          fac2*                                   &
     &                          (tl_cff1*(cff5*dmUdz-dmUde(i  ,j,k1))+  &
     &                           tl_cff2*(cff6*dmUdz-dmUde(i+1,j,k2))+  &
     &                           tl_cff3*(cff7*dmUdz-dmUde(i  ,j,k2))+  &
     &                           tl_cff4*(cff8*dmUdz-dmUde(i+1,j,k1))+  &
     &                           cff1*(tl_cff5*dmUdz+cff5*tl_dmUdz-     &
     &                                 tl_dmUde(i  ,j,k1))+             &
     &                           cff2*(tl_cff6*dmUdz+cff6*tl_dmUdz-     &
     &                                 tl_dmUde(i+1,j,k2))+             &
     &                           cff3*(tl_cff7*dmUdz+cff7*tl_dmUdz-     &
     &                                 tl_dmUde(i  ,j,k2))+             &
     &                           cff4*(tl_cff8*dmUdz+cff8*tl_dmUdz-     &
     &                                 tl_dmUde(i+1,j,k1)))
#ifdef VISC_3DCOEF
                tl_VFse(i,j,k2)=tl_VFse(i,j,k2)+                        &
     &                          tl_fac2*                                &
     &                          (cff1*(cff5*dmUdz-dmUde(i  ,j,k1))+     &
     &                           cff2*(cff6*dmUdz-dmUde(i+1,j,k2))+     &
     &                           cff3*(cff7*dmUdz-dmUde(i  ,j,k2))+     &
     &                           cff4*(cff8*dmUdz-dmUde(i+1,j,k1)))
#endif
              END DO
            END DO
          END IF
!
!  Time-step biharmonic, geopotential viscosity term. Notice that
!  momentum at this stage is HzU and HzV and has m2/s units.  Add
!  contribution for barotropic forcing terms.
#ifdef DIAGNOSTICS_UV
!! The rotated vertical term cannot be split from the horizontal
!! terms because of the 2D/3D momentum coupling.
#endif
!
          DO j=Jstr,Jend
            DO i=IstrU,Iend
              cff=dt(ng)*0.25_r8*(pm(i-1,j)+pm(i,j))*(pn(i-1,j)+pn(i,j))
!>            cff1=0.5_r8*(pn(i-1,j)+pn(i,j))*(UFx(i,j  )-UFx(i-1,j))
!>
              tl_cff1=0.5_r8*(pn(i-1,j)+pn(i,j))*                       &
     &                (tl_UFx(i,j  )-tl_UFx(i-1,j))
!>            cff2=0.5_r8*(pm(i-1,j)+pm(i,j))*(UFe(i,j+1)-UFe(i  ,j))
!>
              tl_cff2=0.5_r8*(pm(i-1,j)+pm(i,j))*                       &
     &                (tl_UFe(i,j+1)-tl_UFe(i  ,j))
!>            cff3=UFsx(i,j,k2)-UFsx(i,j,k1)
!>
              tl_cff3=tl_UFsx(i,j,k2)-tl_UFsx(i,j,k1)
!>            cff4=UFse(i,j,k2)-UFse(i,j,k1)
!>
              tl_cff4=tl_UFse(i,j,k2)-tl_UFse(i,j,k1)
!>            cff5=cff*(cff1+cff2)
!>
              tl_cff5=cff*(tl_cff1+tl_cff2)
!>            cff6=dt(ng)*(cff3+cff4)
!>
              tl_cff6=dt(ng)*(tl_cff3+tl_cff4)
!>            rufrc(i,j)=rufrc(i,j)-cff1-cff2-cff3-cff4
!>
              tl_rufrc(i,j)=tl_rufrc(i,j)-                              &
     &                      tl_cff1-tl_cff2-tl_cff3-tl_cff4
!>            u(i,j,k,nnew)=u(i,j,k,nnew)-cff5-cff6
!>
              tl_u(i,j,k,nnew)=tl_u(i,j,k,nnew)-tl_cff5-tl_cff6
#ifdef DIAGNOSTICS_UV
!!            DiaRUfrc(i,j,3,M2hvis)=DiaRUfrc(i,j,3,M2hvis)-cff1-cff2-  &
!!   &                                                      cff3-cff4
!!            DiaRUfrc(i,j,3,M2xvis)=DiaRUfrc(i,j,3,M2xvis)-cff1-cff3
!!            DiaRUfrc(i,j,3,M2yvis)=DiaRUfrc(i,j,3,M2yvis)-cff2-cff4
!!            DiaU3wrk(i,j,k,M3hvis)=-cff5-cff6
!!            DiaU3wrk(i,j,k,M3xvis)=-cff*cff1-dt(ng)*cff3
!!            DiaU3wrk(i,j,k,M3yvis)=-cff*cff2-dt(ng)*cff4
#endif
            END DO
          END DO

          DO j=JstrV,Jend
            DO i=Istr,Iend
              cff=dt(ng)*0.25_r8*(pm(i,j)+pm(i,j-1))*(pn(i,j)+pn(i,j-1))
!>            cff1=0.5_r8*(pn(i,j-1)+pn(i,j))*(VFx(i+1,j)-VFx(i,j  ))
!>
              tl_cff1=0.5_r8*(pn(i,j-1)+pn(i,j))*                       &
     &                (tl_VFx(i+1,j)-tl_VFx(i,j  ))
!>            cff2=0.5_r8*(pm(i,j-1)+pm(i,j))*(VFe(i  ,j)-VFe(i,j-1))
!>
              tl_cff2=0.5_r8*(pm(i,j-1)+pm(i,j))*                       &
     &                (tl_VFe(i  ,j)-tl_VFe(i,j-1))
!>            cff3=VFsx(i,j,k2)-VFsx(i,j,k1)
!>
              tl_cff3=tl_VFsx(i,j,k2)-tl_VFsx(i,j,k1)
!>            cff4=VFse(i,j,k2)-VFse(i,j,k1)
!>
              tl_cff4=tl_VFse(i,j,k2)-tl_VFse(i,j,k1)
!>            cff5=cff*(cff1-cff2)
!>
              tl_cff5=cff*(tl_cff1-tl_cff2)
!>            cff6=dt(ng)*(cff3+cff4)
!>
              tl_cff6=dt(ng)*(tl_cff3+tl_cff4)
!>            rvfrc(i,j)=rvfrc(i,j)-cff1+cff2-cff3-cff4
!>
              tl_rvfrc(i,j)=tl_rvfrc(i,j)-                              &
     &                      tl_cff1+tl_cff2-tl_cff3-tl_cff4
!>            v(i,j,k,nnew)=v(i,j,k,nnew)-cff5-cff6
!>
              tl_v(i,j,k,nnew)=tl_v(i,j,k,nnew)-tl_cff5-tl_cff6
#ifdef DIAGNOSTICS_UV
!!            DiaRVfrc(i,j,3,M2hvis)=DiaRVfrc(i,j,3,M2hvis)-cff1+cff2-  &
!!   &                                                      cff3-cff4
!!            DiaRVfrc(i,j,3,M2xvis)=DiaRVfrc(i,j,3,M2xvis)-cff1-cff3
!!            DiaRVfrc(i,j,3,M2yvis)=DiaRVfrc(i,j,3,M2yvis)+cff2-cff4
!!            DiaV3wrk(i,j,k,M3hvis)=-cff5-cff6
!!            DiaV3wrk(i,j,k,M3xvis)=-cff*cff1-dt(ng)*cff3
!!            DiaV3wrk(i,j,k,M3yvis)= cff*cff2-dt(ng)*cff4
#endif
            END DO
          END DO
        END IF
      END DO K_LOOP2

      RETURN
      END SUBROUTINE tl_uv3dmix4_tile
