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MODULE zdfiwm
   !!========================================================================
   !!                       ***  MODULE  zdfiwm  ***
   !! Ocean physics: Internal gravity wave-driven vertical mixing
   !!========================================================================
   !! History :  1.0  !  2004-04  (L. Bessieres, G. Madec)  Original code
   !!             -   !  2006-08  (A. Koch-Larrouy)  Indonesian strait
   !!            3.3  !  2010-10  (C. Ethe, G. Madec)  reorganisation of initialisation phase
   !!            3.6  !  2016-03  (C. de Lavergne)  New param: internal wave-driven mixing 
   !!            4.0  !  2017-04  (G. Madec)  renamed module, remove the old param. and the CPP keys
   !!----------------------------------------------------------------------

   !!----------------------------------------------------------------------
   !!   zdf_iwm       : global     momentum & tracer Kz with wave induced Kz
   !!   zdf_iwm_init  : global     momentum & tracer Kz with wave induced Kz
   !!----------------------------------------------------------------------
   USE oce            ! ocean dynamics and tracers variables
   USE dom_oce        ! ocean space and time domain variables
   USE zdf_oce        ! ocean vertical physics variables
   USE zdfddm         ! ocean vertical physics: double diffusive mixing
   USE lbclnk         ! ocean lateral boundary conditions (or mpp link)
   USE eosbn2         ! ocean equation of state
   USE phycst         ! physical constants
   !
   USE fldread        ! field read
   USE prtctl         ! Print control
   USE in_out_manager ! I/O manager
   USE iom            ! I/O Manager
   USE lib_mpp        ! MPP library
   USE lib_fortran    ! Fortran utilities (allows no signed zero when 'key_nosignedzero' defined)  

   IMPLICIT NONE
   PRIVATE

   PUBLIC   zdf_iwm        ! called in step module 
   PUBLIC   zdf_iwm_init   ! called in nemogcm module 

   !                      !!* Namelist  namzdf_iwm : internal wave-driven mixing *
   INTEGER ::  nn_zpyc     ! pycnocline-intensified mixing energy proportional to N (=1) or N^2 (=2)
   LOGICAL ::  ln_mevar    ! variable (=T) or constant (=F) mixing efficiency
   LOGICAL ::  ln_tsdiff   ! account for differential T/S wave-driven mixing (=T) or not (=F)

   REAL(wp)::  r1_6 = 1._wp / 6._wp

   REAL(wp), ALLOCATABLE, SAVE, DIMENSION(:,:) ::   ebot_iwm   ! power available from high-mode wave breaking (W/m2)
   REAL(wp), ALLOCATABLE, SAVE, DIMENSION(:,:) ::   epyc_iwm   ! power available from low-mode, pycnocline-intensified wave breaking (W/m2)
   REAL(wp), ALLOCATABLE, SAVE, DIMENSION(:,:) ::   ecri_iwm   ! power available from low-mode, critical slope wave breaking (W/m2)
   REAL(wp), ALLOCATABLE, SAVE, DIMENSION(:,:) ::   hbot_iwm   ! WKB decay scale for high-mode energy dissipation (m)
   REAL(wp), ALLOCATABLE, SAVE, DIMENSION(:,:) ::   hcri_iwm   ! decay scale for low-mode critical slope dissipation (m)

   !! * Substitutions
#  include "do_loop_substitute.h90"
#  include "domzgr_substitute.h90"
   !!----------------------------------------------------------------------
   !! NEMO/OCE 4.0 , NEMO Consortium (2018)
   !! $Id: zdfiwm.F90 14882 2021-05-18 16:32:47Z gsamson $
   !! Software governed by the CeCILL license (see ./LICENSE)
   !!----------------------------------------------------------------------
CONTAINS

   INTEGER FUNCTION zdf_iwm_alloc()
      !!----------------------------------------------------------------------
      !!                ***  FUNCTION zdf_iwm_alloc  ***
      !!----------------------------------------------------------------------
      ALLOCATE( ebot_iwm(jpi,jpj),  epyc_iwm(jpi,jpj),  ecri_iwm(jpi,jpj) ,     &
      &         hbot_iwm(jpi,jpj),  hcri_iwm(jpi,jpj)                     , STAT=zdf_iwm_alloc )
      !
      CALL mpp_sum ( 'zdfiwm', zdf_iwm_alloc )
      IF( zdf_iwm_alloc /= 0 )   CALL ctl_stop( 'STOP', 'zdf_iwm_alloc: failed to allocate arrays' )
   END FUNCTION zdf_iwm_alloc


   SUBROUTINE zdf_iwm( kt, Kmm, p_avm, p_avt, p_avs )
      !!----------------------------------------------------------------------
      !!                  ***  ROUTINE zdf_iwm  ***
      !!                   
      !! ** Purpose :   add to the vertical mixing coefficients the effect of
      !!              breaking internal waves.
      !!
      !! ** Method  : - internal wave-driven vertical mixing is given by:
      !!                  Kz_wave = min(  100 cm2/s, f(  Reb = zemx_iwm /( Nu * N^2 )  )
      !!              where zemx_iwm is the 3D space distribution of the wave-breaking 
      !!              energy and Nu the molecular kinematic viscosity.
      !!              The function f(Reb) is linear (constant mixing efficiency)
      !!              if the namelist parameter ln_mevar = F and nonlinear if ln_mevar = T.
      !!
      !!              - Compute zemx_iwm, the 3D power density that allows to compute
      !!              Reb and therefrom the wave-induced vertical diffusivity.
      !!              This is divided into three components:
      !!                 1. Bottom-intensified low-mode dissipation at critical slopes
      !!                     zemx_iwm(z) = ( ecri_iwm / rho0 ) * EXP( -(H-z)/hcri_iwm )
      !!                                   / ( 1. - EXP( - H/hcri_iwm ) ) * hcri_iwm
      !!              where hcri_iwm is the characteristic length scale of the bottom 
      !!              intensification, ecri_iwm a map of available power, and H the ocean depth.
      !!                 2. Pycnocline-intensified low-mode dissipation
      !!                     zemx_iwm(z) = ( epyc_iwm / rho0 ) * ( sqrt(rn2(z))^nn_zpyc )
      !!                                   / SUM( sqrt(rn2(z))^nn_zpyc * e3w[z) )
      !!              where epyc_iwm is a map of available power, and nn_zpyc
      !!              is the chosen stratification-dependence of the internal wave
      !!              energy dissipation.
      !!                 3. WKB-height dependent high mode dissipation
      !!                     zemx_iwm(z) = ( ebot_iwm / rho0 ) * rn2(z) * EXP(-z_wkb(z)/hbot_iwm)
      !!                                   / SUM( rn2(z) * EXP(-z_wkb(z)/hbot_iwm) * e3w[z) )
      !!              where hbot_iwm is the characteristic length scale of the WKB bottom 
      !!              intensification, ebot_iwm is a map of available power, and z_wkb is the
      !!              WKB-stretched height above bottom defined as
      !!                    z_wkb(z) = H * SUM( sqrt(rn2(z'>=z)) * e3w[z'>=z) )
      !!                                 / SUM( sqrt(rn2(z'))    * e3w[z')    )
      !!
      !!              - update the model vertical eddy viscosity and diffusivity: 
      !!                     avt  = avt  +    av_wave
      !!                     avm  = avm  +    av_wave
      !!
      !!              - if namelist parameter ln_tsdiff = T, account for differential mixing:
      !!                     avs  = avt  +    av_wave * diffusivity_ratio(Reb)
      !!
      !! ** Action  : - avt, avs, avm, increased by tide internal wave-driven mixing    
      !!
      !! References :  de Lavergne et al. 2015, JPO; 2016, in prep.
      !!----------------------------------------------------------------------
      INTEGER                    , INTENT(in   ) ::   kt             ! ocean time step
      INTEGER                    , INTENT(in   ) ::   Kmm            ! time level index
      REAL(wp), DIMENSION(:,:,:) , INTENT(inout) ::   p_avm          ! momentum Kz (w-points)
      REAL(wp), DIMENSION(:,:,:) , INTENT(inout) ::   p_avt, p_avs   ! tracer   Kz (w-points)
      !
      INTEGER  ::   ji, jj, jk   ! dummy loop indices
      REAL(wp), SAVE :: zztmp
      REAL(wp)       :: ztmp1, ztmp2        ! scalar workspace
      REAL(wp), DIMENSION(A2D(nn_hls))     ::   zfact       ! Used for vertical structure
      REAL(wp), DIMENSION(A2D(nn_hls))     ::   zhdep       ! Ocean depth
      REAL(wp), DIMENSION(A2D(nn_hls),jpk) ::   zwkb        ! WKB-stretched height above bottom
      REAL(wp), DIMENSION(A2D(nn_hls),jpk) ::   zweight     ! Weight for high mode vertical distribution
      REAL(wp), DIMENSION(A2D(nn_hls),jpk) ::   znu_t       ! Molecular kinematic viscosity (T grid)
      REAL(wp), DIMENSION(A2D(nn_hls),jpk) ::   znu_w       ! Molecular kinematic viscosity (W grid)
      REAL(wp), DIMENSION(A2D(nn_hls),jpk) ::   zReb        ! Turbulence intensity parameter
      REAL(wp), DIMENSION(A2D(nn_hls),jpk) ::   zemx_iwm    ! local energy density available for mixing (W/kg)
      REAL(wp), DIMENSION(A2D(nn_hls),jpk) ::   zav_ratio   ! S/T diffusivity ratio (only for ln_tsdiff=T)
      REAL(wp), DIMENSION(A2D(nn_hls),jpk) ::   zav_wave    ! Internal wave-induced diffusivity
      REAL(wp), ALLOCATABLE, DIMENSION(:,:,:) ::   z3d  ! 3D workspace used for iom_put 
      REAL(wp), ALLOCATABLE, DIMENSION(:,:)   ::   z2d  ! 2D     -      -    -     -
      !!----------------------------------------------------------------------
      !
      !                       
      ! Set to zero the 1st and last vertical levels of appropriate variables
      IF( iom_use("emix_iwm") ) THEN
         zemx_iwm(:,:,:) = 0._wp
      ENDIF
      IF( iom_use("av_ratio") ) THEN
         zav_ratio(:,:,:) = 0._wp
      ENDIF
      IF( iom_use("av_wave") .OR. sn_cfctl%l_prtctl ) THEN
         zav_wave(:,:,:) = 0._wp
      ENDIF
      !
      !                       ! ----------------------------- !
      !                       !  Internal wave-driven mixing  !  (compute zav_wave)
      !                       ! ----------------------------- !
      !                             
      !                       !* Critical slope mixing: distribute energy over the time-varying ocean depth,
      !                                                 using an exponential decay from the seafloor.
      DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )             ! part independent of the level
         zhdep(ji,jj) = gdepw_0(ji,jj,mbkt(ji,jj)+1)       ! depth of the ocean
         zfact(ji,jj) = rho0 * (  1._wp - EXP( -zhdep(ji,jj) / hcri_iwm(ji,jj) )  )
         IF( zfact(ji,jj) /= 0._wp )   zfact(ji,jj) = ecri_iwm(ji,jj) / zfact(ji,jj)
      END_2D
!!gm gde3w ==>>>  check for ssh taken into account.... seem OK gde3w_n=gdept(:,:,:,Kmm) - ssh(:,:,Kmm)
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )   ! complete with the level-dependent part
         IF ( zfact(ji,jj) == 0._wp .OR. wmask(ji,jj,jk) == 0._wp ) THEN   ! optimization
            zemx_iwm(ji,jj,jk) = 0._wp
         ELSE
            zemx_iwm(ji,jj,jk) = zfact(ji,jj) * (  EXP( ( gde3w(ji,jj,jk  ) - zhdep(ji,jj) ) / hcri_iwm(ji,jj) )     &
                 &                               - EXP( ( gde3w(ji,jj,jk-1) - zhdep(ji,jj) ) / hcri_iwm(ji,jj) ) )   &
                 &                            / ( gde3w(ji,jj,jk) - gde3w(ji,jj,jk-1) )
         ENDIF
      END_3D
!!gm delta(gde3w) = e3t(:,:,:,Kmm)  !!  Please verify the grid-point position w versus t-point
!!gm it seems to me that only 1/hcri_iwm  is used ==>  compute it one for all


      !                        !* Pycnocline-intensified mixing: distribute energy over the time-varying 
      !                        !* ocean depth as proportional to sqrt(rn2)^nn_zpyc
      !                                          ! (NB: N2 is masked, so no use of wmask here)
      SELECT CASE ( nn_zpyc )
      !
      CASE ( 1 )               ! Dissipation scales as N (recommended)
         !
         DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
            zfact(ji,jj) = 0._wp
         END_2D
         DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )       ! part independent of the level
            zfact(ji,jj) = zfact(ji,jj) + e3w(ji,jj,jk,Kmm) * SQRT(  MAX( 0._wp, rn2(ji,jj,jk) )  ) * wmask(ji,jj,jk)
         END_3D
         !
         DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
            IF( zfact(ji,jj) /= 0 )   zfact(ji,jj) = epyc_iwm(ji,jj) / ( rho0 * zfact(ji,jj) )
         END_2D
         !
         DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )       ! complete with the level-dependent part
            zemx_iwm(ji,jj,jk) = zemx_iwm(ji,jj,jk) + zfact(ji,jj) * SQRT(  MAX( 0._wp, rn2(ji,jj,jk) )  ) * wmask(ji,jj,jk)
         END_3D
         !
      CASE ( 2 )               ! Dissipation scales as N^2
         !
         DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
            zfact(ji,jj) = 0._wp
         END_2D
         DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )       ! part independent of the level
            zfact(ji,jj) = zfact(ji,jj) + e3w(ji,jj,jk,Kmm) * MAX( 0._wp, rn2(ji,jj,jk) ) * wmask(ji,jj,jk)
         END_3D
         !
         DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
            IF( zfact(ji,jj) /= 0 )   zfact(ji,jj) = epyc_iwm(ji,jj) / ( rho0 * zfact(ji,jj) )
         END_2D
         !
         DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )
            zemx_iwm(ji,jj,jk) = zemx_iwm(ji,jj,jk) + zfact(ji,jj) * MAX( 0._wp, rn2(ji,jj,jk) ) * wmask(ji,jj,jk)
         END_3D
         !
      END SELECT

      !                        !* WKB-height dependent mixing: distribute energy over the time-varying 
      !                        !* ocean depth as proportional to rn2 * exp(-z_wkb/rn_hbot)
      !
      DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
         zwkb(ji,jj,1) = 0._wp
      END_2D
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )
         zwkb(ji,jj,jk) = zwkb(ji,jj,jk-1) + e3w(ji,jj,jk,Kmm) * SQRT(  MAX( 0._wp, rn2(ji,jj,jk) )  ) * wmask(ji,jj,jk)
      END_3D
      DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
         zfact(ji,jj) = zwkb(ji,jj,jpkm1)
      END_2D
      !
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )
         IF( zfact(ji,jj) /= 0 )   zwkb(ji,jj,jk) = zhdep(ji,jj) * ( zfact(ji,jj) - zwkb(ji,jj,jk) )   &
            &                                     * wmask(ji,jj,jk) / zfact(ji,jj)
      END_3D
      DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
         zwkb (ji,jj,1) = zhdep(ji,jj) * wmask(ji,jj,1)
      END_2D
      !
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )
         IF ( rn2(ji,jj,jk) <= 0._wp .OR. wmask(ji,jj,jk) == 0._wp ) THEN   ! optimization: EXP coast a lot
            zweight(ji,jj,jk) = 0._wp
         ELSE
            zweight(ji,jj,jk) = rn2(ji,jj,jk) * hbot_iwm(ji,jj)    &
               &   * (  EXP( -zwkb(ji,jj,jk) / hbot_iwm(ji,jj) ) - EXP( -zwkb(ji,jj,jk-1) / hbot_iwm(ji,jj) )  )
         ENDIF
      END_3D
      !
      DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
         zfact(ji,jj) = 0._wp
      END_2D
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )       ! part independent of the level
         zfact(ji,jj) = zfact(ji,jj) + zweight(ji,jj,jk)
      END_3D
      !
      DO_2D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1 )
         IF( zfact(ji,jj) /= 0 )   zfact(ji,jj) = ebot_iwm(ji,jj) / ( rho0 * zfact(ji,jj) )
      END_2D
      !
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )       ! complete with the level-dependent part
         zemx_iwm(ji,jj,jk) = zemx_iwm(ji,jj,jk) + zweight(ji,jj,jk) * zfact(ji,jj) * wmask(ji,jj,jk)   &
            &                                                        / ( gde3w(ji,jj,jk) - gde3w(ji,jj,jk-1) )
!!gm  use of e3t(ji,jj,:,Kmm) just above?
      END_3D
      !
!!gm  this is to be replaced by just a constant value znu=1.e-6 m2/s
      ! Calculate molecular kinematic viscosity
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 1, jpkm1 )
         znu_t(ji,jj,jk) = 1.e-4_wp * (  17.91_wp - 0.53810_wp * ts(ji,jj,jk,jp_tem,Kmm)   &
            &                                     + 0.00694_wp * ts(ji,jj,jk,jp_tem,Kmm) * ts(ji,jj,jk,jp_tem,Kmm)  &
            &                                     + 0.02305_wp * ts(ji,jj,jk,jp_sal,Kmm)  ) * tmask(ji,jj,jk) * r1_rho0
      END_3D
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )
         znu_w(ji,jj,jk) = 0.5_wp * ( znu_t(ji,jj,jk-1) + znu_t(ji,jj,jk) ) * wmask(ji,jj,jk)
      END_3D
!!gm end
      !
      ! Calculate turbulence intensity parameter Reb
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )
         zReb(ji,jj,jk) = zemx_iwm(ji,jj,jk) / MAX( 1.e-20_wp, znu_w(ji,jj,jk) * rn2(ji,jj,jk) )
      END_3D
      !
      ! Define internal wave-induced diffusivity
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )
         zav_wave(ji,jj,jk) = znu_w(ji,jj,jk) * zReb(ji,jj,jk) * r1_6   ! This corresponds to a constant mixing efficiency of 1/6
      END_3D
      !
      IF( ln_mevar ) THEN                ! Variable mixing efficiency case : modify zav_wave in the
         DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )   ! energetic (Reb > 480) and buoyancy-controlled (Reb <10.224 ) regimes
            IF( zReb(ji,jj,jk) > 480.00_wp ) THEN
               zav_wave(ji,jj,jk) = 3.6515_wp * znu_w(ji,jj,jk) * SQRT( zReb(ji,jj,jk) )
            ELSEIF( zReb(ji,jj,jk) < 10.224_wp ) THEN
               zav_wave(ji,jj,jk) = 0.052125_wp * znu_w(ji,jj,jk) * zReb(ji,jj,jk) * SQRT( zReb(ji,jj,jk) )
            ENDIF
         END_3D
      ENDIF
      !
      DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )      ! Bound diffusivity by molecular value and 100 cm2/s
         zav_wave(ji,jj,jk) = MIN(  MAX( 1.4e-7_wp, zav_wave(ji,jj,jk) ), 1.e-2_wp  ) * wmask(ji,jj,jk)
      END_3D
      !
      IF( kt == nit000 ) THEN        !* Control print at first time-step: diagnose the energy consumed by zav_wave
         IF( .NOT. l_istiled .OR. ntile == 1 ) zztmp = 0._wp                    ! Do only on the first tile
!!gm used of glosum 3D....
         DO_3D( 0, 0, 0, 0, 2, jpkm1 )
            zztmp = zztmp + e3w(ji,jj,jk,Kmm) * e1e2t(ji,jj)   &
               &          * MAX( 0._wp, rn2(ji,jj,jk) ) * zav_wave(ji,jj,jk) * wmask(ji,jj,jk) * tmask_i(ji,jj)
         END_3D

         IF( .NOT. l_istiled .OR. ntile == nijtile ) THEN                       ! Do only on the last tile
            CALL mpp_sum( 'zdfiwm', zztmp )
            zztmp = rho0 * zztmp ! Global integral of rauo * Kz * N^2 = power contributing to mixing
            !
            IF(lwp) THEN
               WRITE(numout,*)
               WRITE(numout,*) 'zdf_iwm : Internal wave-driven mixing (iwm)'
               WRITE(numout,*) '~~~~~~~ '
               WRITE(numout,*)
               WRITE(numout,*) '      Total power consumption by av_wave =  ', zztmp * 1.e-12_wp, 'TW'
            ENDIF
         ENDIF
      ENDIF

      !                          ! ----------------------- !
      !                          !   Update  mixing coefs  !                          
      !                          ! ----------------------- !
      !      
      IF( ln_tsdiff ) THEN                !* Option for differential mixing of salinity and temperature
         ztmp1 = 0.505_wp + 0.495_wp * TANH( 0.92_wp * ( LOG10( 1.e-20_wp ) - 0.60_wp ) )
         DO_3D( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )       ! Calculate S/T diffusivity ratio as a function of Reb
            ztmp2 = zReb(ji,jj,jk) * 5._wp * r1_6
            IF ( ztmp2 > 1.e-20_wp .AND. wmask(ji,jj,jk) == 1._wp ) THEN
               zav_ratio(ji,jj,jk) = 0.505_wp + 0.495_wp * TANH( 0.92_wp * ( LOG10(ztmp2) - 0.60_wp ) )
            ELSE
               zav_ratio(ji,jj,jk) = ztmp1 * wmask(ji,jj,jk)
            ENDIF
         END_3D
         CALL iom_put( "av_ratio", zav_ratio )
         DO_3D_OVR( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )    !* update momentum & tracer diffusivity with wave-driven mixing
            p_avs(ji,jj,jk) = p_avs(ji,jj,jk) + zav_wave(ji,jj,jk) * zav_ratio(ji,jj,jk)
            p_avt(ji,jj,jk) = p_avt(ji,jj,jk) + zav_wave(ji,jj,jk)
            p_avm(ji,jj,jk) = p_avm(ji,jj,jk) + zav_wave(ji,jj,jk)
         END_3D
         !
      ELSE                                !* update momentum & tracer diffusivity with wave-driven mixing
         DO_3D_OVR( nn_hls-1, nn_hls-1, nn_hls-1, nn_hls-1, 2, jpkm1 )
            p_avs(ji,jj,jk) = p_avs(ji,jj,jk) + zav_wave(ji,jj,jk)
            p_avt(ji,jj,jk) = p_avt(ji,jj,jk) + zav_wave(ji,jj,jk)
            p_avm(ji,jj,jk) = p_avm(ji,jj,jk) + zav_wave(ji,jj,jk)
         END_3D
      ENDIF

      !                                   !* output internal wave-driven mixing coefficient
      CALL iom_put( "av_wave", zav_wave )
                                          !* output useful diagnostics: Kz*N^2 , 
!!gm Kz*N2 should take into account the ratio avs/avt if it is used.... (see diaar5)
                                          !  vertical integral of rho0 * Kz * N^2 , energy density (zemx_iwm)
      IF( iom_use("bflx_iwm") .OR. iom_use("pcmap_iwm") ) THEN
         ALLOCATE( z2d(A2D(nn_hls)) , z3d(A2D(nn_hls),jpk) )
         ! Initialisation for iom_put
         z2d(:,:) = 0._wp ; z3d(:,:,:) = 0._wp

         DO_3D( 0, 0, 0, 0, 2, jpkm1 )
            z3d(ji,jj,jk) = MAX( 0._wp, rn2(ji,jj,jk) ) * zav_wave(ji,jj,jk)
            z2d(ji,jj) = z2d(ji,jj) + e3w(ji,jj,jk,Kmm) * z3d(ji,jj,jk) * wmask(ji,jj,jk)
         END_3D
         DO_2D( 0, 0, 0, 0 )
            z2d(ji,jj) = rho0 * z2d(ji,jj)
         END_2D
         CALL iom_put(  "bflx_iwm", z3d )
         CALL iom_put( "pcmap_iwm", z2d )
         DEALLOCATE( z2d , z3d )
      ENDIF
      CALL iom_put( "emix_iwm", zemx_iwm )
      
      IF(sn_cfctl%l_prtctl)   CALL prt_ctl(tab3d_1=zav_wave , clinfo1=' iwm - av_wave: ', tab3d_2=avt, clinfo2=' avt: ', kdim=jpk)
      !
   END SUBROUTINE zdf_iwm


   SUBROUTINE zdf_iwm_init
      !!----------------------------------------------------------------------
      !!                  ***  ROUTINE zdf_iwm_init  ***
      !!                     
      !! ** Purpose :   Initialization of the wave-driven vertical mixing, reading
      !!              of input power maps and decay length scales in netcdf files.
      !!
      !! ** Method  : - Read the namzdf_iwm namelist and check the parameters
      !!
      !!              - Read the input data in NetCDF files :
      !!              power available from high-mode wave breaking (mixing_power_bot.nc)
      !!              power available from pycnocline-intensified wave-breaking (mixing_power_pyc.nc)
      !!              power available from critical slope wave-breaking (mixing_power_cri.nc)
      !!              WKB decay scale for high-mode wave-breaking (decay_scale_bot.nc)
      !!              decay scale for critical slope wave-breaking (decay_scale_cri.nc)
      !!
      !! ** input   : - Namlist namzdf_iwm
      !!              - NetCDF files : mixing_power_bot.nc, mixing_power_pyc.nc, mixing_power_cri.nc,
      !!              decay_scale_bot.nc decay_scale_cri.nc
      !!
      !! ** Action  : - Increase by 1 the nstop flag is setting problem encounter
      !!              - Define ebot_iwm, epyc_iwm, ecri_iwm, hbot_iwm, hcri_iwm
      !!
      !! References : de Lavergne et al. JPO, 2015 ; de Lavergne PhD 2016
      !!              de Lavergne et al. in prep., 2017
      !!----------------------------------------------------------------------
      INTEGER  ::   ifpr               ! dummy loop indices
      INTEGER  ::   inum               ! local integer
      INTEGER  ::   ios
      REAL(wp) ::   zbot, zpyc, zcri   ! local scalars
      !
      CHARACTER(len=256)            ::   cn_dir                 ! Root directory for location of ssr files
      INTEGER, PARAMETER            ::   jpiwm  = 5             ! maximum number of files to read
      INTEGER, PARAMETER            ::   jp_mpb = 1
      INTEGER, PARAMETER            ::   jp_mpp = 2
      INTEGER, PARAMETER            ::   jp_mpc = 3
      INTEGER, PARAMETER            ::   jp_dsb = 4
      INTEGER, PARAMETER            ::   jp_dsc = 5
      !
      TYPE(FLD_N), DIMENSION(jpiwm) ::   slf_iwm                ! array of namelist informations
      TYPE(FLD_N)                   ::   sn_mpb, sn_mpp, sn_mpc ! informations about Mixing Power field to be read
      TYPE(FLD_N)                   ::   sn_dsb, sn_dsc         ! informations about Decay Scale field to be read
      TYPE(FLD  ), DIMENSION(jpiwm) ::   sf_iwm                 ! structure of input fields (file informations, fields read)
      !
      NAMELIST/namzdf_iwm/ nn_zpyc, ln_mevar, ln_tsdiff, &
         &                 cn_dir, sn_mpb, sn_mpp, sn_mpc, sn_dsb, sn_dsc
      !!----------------------------------------------------------------------
      !
      READ  ( numnam_ref, namzdf_iwm, IOSTAT = ios, ERR = 901)
901   IF( ios /= 0 )   CALL ctl_nam ( ios , 'namzdf_iwm in reference namelist' )
      !
      READ  ( numnam_cfg, namzdf_iwm, IOSTAT = ios, ERR = 902 )
902   IF( ios >  0 )   CALL ctl_nam ( ios , 'namzdf_iwm in configuration namelist' )
      IF(lwm) WRITE ( numond, namzdf_iwm )
      !
      IF(lwp) THEN                  ! Control print
         WRITE(numout,*)
         WRITE(numout,*) 'zdf_iwm_init : internal wave-driven mixing'
         WRITE(numout,*) '~~~~~~~~~~~~'
         WRITE(numout,*) '   Namelist namzdf_iwm : set wave-driven mixing parameters'
         WRITE(numout,*) '      Pycnocline-intensified diss. scales as N (=1) or N^2 (=2) = ', nn_zpyc
         WRITE(numout,*) '      Variable (T) or constant (F) mixing efficiency            = ', ln_mevar
         WRITE(numout,*) '      Differential internal wave-driven mixing (T) or not (F)   = ', ln_tsdiff
      ENDIF
      
      ! The new wave-driven mixing parameterization elevates avt and avm in the interior, and
      ! ensures that avt remains larger than its molecular value (=1.4e-7). Therefore, avtb should 
      ! be set here to a very small value, and avmb to its (uniform) molecular value (=1.4e-6).
      avmb(:) = 1.4e-6_wp        ! viscous molecular value
      avtb(:) = 1.e-10_wp        ! very small diffusive minimum (background avt is specified in zdf_iwm)    
      avtb_2d(:,:) = 1.e0_wp     ! uniform 
      IF(lwp) THEN                  ! Control print
         WRITE(numout,*)
         WRITE(numout,*) '   Force the background value applied to avm & avt in TKE to be everywhere ',   &
            &               'the viscous molecular value & a very small diffusive value, resp.'
      ENDIF
            
      !                             ! allocate iwm arrays
      IF( zdf_iwm_alloc() /= 0 )   CALL ctl_stop( 'STOP', 'zdf_iwm_init : unable to allocate iwm arrays' )
      !
      ! store namelist information in an array
      slf_iwm(jp_mpb) = sn_mpb ; slf_iwm(jp_mpp) = sn_mpp ; slf_iwm(jp_mpc) = sn_mpc
      slf_iwm(jp_dsb) = sn_dsb ; slf_iwm(jp_dsc) = sn_dsc
      !
      DO ifpr= 1, jpiwm
         ALLOCATE( sf_iwm(ifpr)%fnow(jpi,jpj,1)   )
         IF( slf_iwm(ifpr)%ln_tint )ALLOCATE( sf_iwm(ifpr)%fdta(jpi,jpj,1,2) )
      END DO

      ! fill sf_iwm with sf_iwm and control print
      CALL fld_fill( sf_iwm, slf_iwm , cn_dir, 'zdfiwm_init', 'iwm input file', 'namiwm' )

      !                             ! hard-coded default definition (to be defined in namelist ?)
      sf_iwm(jp_mpb)%fnow(:,:,1) = 1.e-6
      sf_iwm(jp_mpp)%fnow(:,:,1) = 1.e-6
      sf_iwm(jp_mpc)%fnow(:,:,1) = 1.e-10
      sf_iwm(jp_dsb)%fnow(:,:,1) = 100.
      sf_iwm(jp_dsc)%fnow(:,:,1) = 100.

      !                             ! read necessary fields
      CALL fld_read( nit000, 1, sf_iwm )

      ebot_iwm(:,:) = sf_iwm(1)%fnow(:,:,1) * ssmask(:,:) ! energy flux for high-mode wave breaking [W/m2]
      epyc_iwm(:,:) = sf_iwm(2)%fnow(:,:,1) * ssmask(:,:) ! energy flux for pynocline-intensified wave breaking [W/m2]
      ecri_iwm(:,:) = sf_iwm(3)%fnow(:,:,1) * ssmask(:,:) ! energy flux for critical slope wave breaking [W/m2]
      hbot_iwm(:,:) = sf_iwm(4)%fnow(:,:,1)               ! spatially variable decay scale for high-mode wave breaking [m]
      hcri_iwm(:,:) = sf_iwm(5)%fnow(:,:,1)               ! spatially variable decay scale for critical slope wave breaking [m]

      zbot = glob_sum( 'zdfiwm', e1e2t(:,:) * ebot_iwm(:,:) )
      zpyc = glob_sum( 'zdfiwm', e1e2t(:,:) * epyc_iwm(:,:) )
      zcri = glob_sum( 'zdfiwm', e1e2t(:,:) * ecri_iwm(:,:) )

      IF(lwp) THEN
         WRITE(numout,*) '      High-mode wave-breaking energy:             ', zbot * 1.e-12_wp, 'TW'
         WRITE(numout,*) '      Pycnocline-intensifed wave-breaking energy: ', zpyc * 1.e-12_wp, 'TW'
         WRITE(numout,*) '      Critical slope wave-breaking energy:        ', zcri * 1.e-12_wp, 'TW'
      ENDIF
      !
   END SUBROUTINE zdf_iwm_init

   !!======================================================================
END MODULE zdfiwm