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 module ice

!BOP
! !MODULE: ice
!
! !DESCRIPTION:
!  This module currently contains routines for computing ice 
!  formation and the heat flux associated with ice formation.
!  This heat flux is sent to the ice model via the flux coupler.
!  In the future, this module could contain the driver for a
!  subroutinized ice model.
!
! !REVISION HISTORY:
!  SVN:$Id: ice.F90 17759 2009-08-12 20:20:36Z njn01 $

! !USES:

   use TIMCOM_KindsMod
   use TIMCOM_IOUnitsMod

   use kinds_mod, only: int_kind, log_kind, char_len, r8
   use blocks, only: nx_block, ny_block, block
   use domain_size
   use constants, only: cp_sw, latent_heat_fusion, delim_fmt, blank_fmt,     &
       sea_ice_salinity, ppt_to_salt, ocn_ref_salinity, c0, p5, hflux_factor,&
       grav, eps2, ndelim_fmt
   use broadcast, only: broadcast_scalar
   use communicate, only: my_task, master_task
   use io_types, only: nml_in, nml_filename, stdout
   use time_management, only: freq_opt_never, freq_opt_nyear, freq_opt_nday, &
       freq_opt_nhour, freq_opt_nsecond, freq_opt_nstep, init_time_flag,     &
       max_blocks_clinic, km, nt, avg_ts, back_to_back, dtt, check_time_flag,&
       partial_bottom_cells, KMT, DZT, DZ, freq_opt_nmonth, dt, tmix_matsuno,&
       tmix_iopt, ice_ts, access_time_flag
   use exit_mod, only: sigAbort, exit_timcom, flushm
   use prognostic
!   use passive_tracers, only: tracer_ref_val
   use grid!, only: sfc_layer_varthick, sfc_layer_type

   implicit none
   private
   save

! !PUBLIC MEMBER FUNCTIONS:

   public :: init_ice,           &
             increment_tlast_ice,&
!             ice_formation,      &
!             tfreez,             &
!             ice_flx_to_coupler, &
!             tmelt
             tavg_increment_sum_qflux

! !PUBLIC DATA MEMBERS:

   logical (log_kind), public :: &
      liceform            ! flag to turn on/off ice formation

   logical (log_kind), public :: &
      lactive_ice         ! T ==> ocn is coupled to an active ice model
                          ! F ==> ocn is coupled to a dummy ice model

   integer (int_kind), public :: &
      ice_cpl_flag        ! time flag id for coupled timestep

   real (r8), public ::  &
      tlast_ice,         &! time since last ice flux computed
      time_weight,       &
      salice              ! sea ice salinity in msu

   real (r8), dimension(:,:,:), allocatable, public :: &
      AQICE,             &! sum of accumulated ice heat flux since tlast
      QFLUX,             &! internal ocn heat flux due to ice formation
      QICE                ! tot column cooling from ice form (in C*cm)

   real (r8), dimension(nx_block,ny_block,max_blocks_clinic), public ::  &
      FW_FREEZE  ! water flux at T points due to frazil ice formation

   real (r8), public ::  &
      cp_over_lhfusion    ! cp_sw/latent_heat_fusion

   real (r8), public ::  &
      tavg_sum_qflux
!EOP
!BOC
!-----------------------------------------------------------------------
!
!  module variables
!
!-----------------------------------------------------------------------

   integer (int_kind) :: &
      ice_flag,          &! time flag id for ice formation
      kmxice              ! lowest level from which to integrate 
                          ! ice formation

   real (r8) ::          &
      salref              ! ocean ref salinity in msu


!EOC
!***********************************************************************

 contains

!***********************************************************************
!BOP
! !IROUTINE:
! !INTERFACE:

 subroutine init_ice

! !DESCRIPTION:
!  This routine initializes ice variables.  It must be called
!  before initializing restarts because this module add the accumulated
!  ice heat flux to the restart file.
!
! !REVISION HISTORY:
!  same as module

!EOP
!BOC
!-----------------------------------------------------------------------
!
!  local variables
!
!-----------------------------------------------------------------------

   integer (int_kind) ::   &
      nml_error             ! namelist i/o error flag

   character (char_len) :: &
      ice_freq_opt          ! option for frequency of computing ice

   integer (int_kind)   :: &
      ice_freq_iopt,       &! int option for freq units
      ice_freq              ! freq for computing ice in above units


   namelist /ice_nml/ kmxice, ice_freq_opt, ice_freq, lactive_ice

!-----------------------------------------------------------------------
!
!  read input namelists
!
!-----------------------------------------------------------------------

   cp_over_lhfusion = rho_sw*cp_sw/(latent_heat_fusion*rho_fw)

   kmxice           = 1
   ice_freq_opt     = 'never'
   ice_freq         = 100000
   lactive_ice      = .false.

   if (my_task == master_task) then
      open (nml_in, file=nml_filename, status='old',iostat=nml_error)
      if (nml_error /= 0) then
         nml_error = -1
      else
         nml_error =  1
      endif
      do while (nml_error > 0)
         read(nml_in, nml=ice_nml,iostat=nml_error)
      end do
      if (nml_error == 0) close(nml_in)
   endif

   call broadcast_scalar(nml_error, master_task)
   if (nml_error /= 0) then
      call exit_TIMCOM(sigAbort,'ERROR reading ice_nml')
   endif

   if (my_task == master_task) then
      write(stdout,blank_fmt)
      write(stdout,ndelim_fmt)
      write(stdout,blank_fmt)
      write(stdout,*) 'Ice:'
      write(stdout,blank_fmt)
      write(stdout,*) ' ice_nml namelist settings:'
      write(stdout,blank_fmt)
      write(stdout,ice_nml)
      write(stdout,delim_fmt)

      !***
      !*** define salice and salref in msu
      !***
 
      salice = sea_ice_salinity*ppt_to_salt
      salref = ocn_ref_salinity*ppt_to_salt

      liceform = .true.

      select case (ice_freq_opt)
      case ('never')
         write(stdout,'(a22)') 'Ice formation disabled'
         liceform = .false.
         ice_freq_iopt = freq_opt_never
      case ('coupled')
         write(stdout,'(a44)') &
           'Ice formation computed on coupler time steps'
         ice_freq_iopt = freq_opt_never ! check coupler flag instead
      case ('nyear')
         write(stdout,'(a29,i4,a9)') 'Ice formation computed every ', &
                                      ice_freq,' years.  '
         ice_freq_iopt = freq_opt_nyear
      case ('nmonth')
         write(stdout,'(a29,i4,a9)') 'Ice formation computed every ', &
                                      ice_freq,' months. '
         ice_freq_iopt = freq_opt_nmonth
      case ('nday')
         write(stdout,'(a29,i4,a9)') 'Ice formation computed every ', &
                                      ice_freq,' days.   '
         ice_freq_iopt = freq_opt_nday
      case ('nhour')
         write(stdout,'(a29,i4,a9)') 'Ice formation computed every ', &
                                      ice_freq,' hours.  '
         ice_freq_iopt = freq_opt_nhour
      case ('nsecond')
         write(stdout,'(a29,i4,a9)') 'Ice formation computed every ', &
                                      ice_freq,' seconds.'
         ice_freq_iopt = freq_opt_nsecond
      case ('nstep')
         write(stdout,'(a29,i4,a9)') 'Ice formation computed every ', &
                                      ice_freq,' steps.  '
         ice_freq_iopt = freq_opt_nstep
      case default
         ice_freq_iopt = -1000
      end select

      if (liceform) then
         write(stdout,'(a20,1pe10.3)') 'Ice salinity(ppt) = ', &
                                        sea_ice_salinity
         write(stdout,'(a30,i3,a13)') 'Ice formation computed in top ', &
                                       kmxice, ' levels only.'
      endif
      call TIMCOM_IOUnitsFlush(TIMCOM_stdout) ; call TIMCOM_IOUnitsFlush(stdout)

   endif

   call broadcast_scalar(ice_freq_iopt, master_task)
   call broadcast_scalar(lactive_ice,   master_task)

   if (ice_freq_iopt == -1000) then
      call exit_TIMCOM(sigAbort,'unknown restart frequency option')
   endif

   call broadcast_scalar(liceform,      master_task)

!-----------------------------------------------------------------------
!
!  if ice turned on, broadcast remaining vars and allocate memory
!
!-----------------------------------------------------------------------

   if (liceform) then
      call broadcast_scalar(ice_freq, master_task)
      call broadcast_scalar(kmxice,   master_task)
      call broadcast_scalar(salice,   master_task)
      call broadcast_scalar(salref,   master_task)
 
      !***
      !*** set up ice time flag and get coupled_ts id for local use
      !***

      call init_time_flag('ice',ice_flag, default=.false.,  &
                           owner    = 'init_ice',           &
                           freq_opt = ice_freq_iopt,        &
                           freq     = ice_freq)

      call access_time_flag('coupled_ts', ice_cpl_flag)

      !***
      !*** must keep track of time since last ice flux computed
      !***

      tlast_ice = c0

      !***
      !*** allocate and initialize ice flux arrays
      !***

      allocate( QICE(nx_block,ny_block,max_blocks_clinic), & 
               AQICE(nx_block,ny_block,max_blocks_clinic), &
               QFLUX(nx_block,ny_block,max_blocks_clinic))

      QICE  = c0
      AQICE = c0
      QFLUX = c0

   endif

   FW_FREEZE = c0


!-----------------------------------------------------------------------
!EOC

 call flushm (stdout)

 end subroutine init_ice

!***********************************************************************
!BOP
! !IROUTINE:
! !INTERFACE:
   subroutine increment_tlast_ice
use var, only: daodt
! !DESCRIPTION:
!  This subroutine increments tlast_ice in a nonthreaded region.

! !REVISION HISTORY:
!  same as module

!EOP
!BOC

!-----------------------------------------------------------------------
!
!  increment time since last evaluation
!
!-----------------------------------------------------------------------

!   if (avg_ts .or. back_to_back) then
!     time_weight = p5
!   else
     time_weight = c1
!   endif

!   tlast_ice = tlast_ice + dtt*time_weight
   tlast_ice = tlast_ice + (86400.d0/daodt)*time_weight

!-----------------------------------------------------------------------
!EOC

 end subroutine increment_tlast_ice

!***********************************************************************
!***********************************************************************
!BOP
! !IROUTINE: tavg_increment_sum_qflux
! !INTERFACE:

 subroutine tavg_increment_sum_qflux(const)

! !DESCRIPTION:
!  Increment the scalar tavg_sum_qflux with the weight for this timestep.
!
! !REVISION HISTORY:
!  same as module

! !INPUT PARAMETERS:

   real (r8), intent(in) ::  &
      const
!EOP
!BOC
!-----------------------------------------------------------------------

     tavg_sum_qflux = tavg_sum_qflux + const ! const = tlast_ice

!-----------------------------------------------------------------------
!EOC

 end subroutine tavg_increment_sum_qflux


!***********************************************************************
!***********************************************************************

 end module ice

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