! SVN:$Id: ice_meltpond_cesm.F90 1304 2015-11-12 19:28:14Z afrobert@nps.edu $ !======================================================================= ! CESM meltpond parameterization ! ! This meltpond parameterization was developed for use with the delta- ! Eddington radiation scheme, and only affects the radiation budget in ! the model. That is, although the pond volume is tracked, that liquid ! water is not used elsewhere in the model for mass budgets or other ! physical processes. ! ! authors David A. Bailey (NCAR) ! Marika M. Holland (NCAR) ! Elizabeth C. Hunke (LANL) module ice_meltpond_cesm use ice_kinds_mod use ice_constants implicit none private public :: init_meltponds_cesm, compute_ponds_cesm, & write_restart_pond_cesm, read_restart_pond_cesm logical (kind=log_kind), public :: & restart_pond_cesm ! if .true., read meltponds restart file real (kind=dbl_kind), public :: & hs0 ! snow depth for transition to bare sea ice (m) !======================================================================= contains !======================================================================= ! Initialize melt ponds. subroutine init_meltponds_cesm(nx_block, ny_block, ncat, & apnd, hpnd) integer(kind=int_kind), intent(in) :: & nx_block , & ny_block , & ncat real(kind=dbl_kind), dimension(nx_block,ny_block,ncat), & intent(out) :: & apnd , & ! melt pond area fraction hpnd ! melt pond depth apnd(:,:,:) = c0 hpnd(:,:,:) = c0 end subroutine init_meltponds_cesm !======================================================================= subroutine compute_ponds_cesm(nx_block,ny_block, & ilo, ihi, jlo, jhi, & dt, hi_min, & pndaspect, & rfrac, meltt, & melts, frain, & aicen, vicen, vsnon, & Tsfcn, apnd, hpnd) integer (kind=int_kind), intent(in) :: & nx_block, ny_block, & ! block dimensions ilo,ihi,jlo,jhi ! beginning and end of physical domain real (kind=dbl_kind), intent(in) :: & dt, & ! time step (s) hi_min, & ! minimum ice thickness allowed for thermo (m) pndaspect ! ratio of pond depth to pond fraction real (kind=dbl_kind), dimension(nx_block,ny_block), & intent(in) :: & rfrac, & ! water fraction retained for melt ponds meltt, & melts, & frain, & aicen, & vicen, & vsnon real (kind=dbl_kind), dimension(nx_block,ny_block), & intent(in) :: & Tsfcn real (kind=dbl_kind), dimension(nx_block,ny_block), & intent(inout) :: & apnd, & hpnd ! local temporary variables real (kind=dbl_kind), dimension(nx_block,ny_block) :: & volpn integer (kind=int_kind), dimension (nx_block*ny_block) :: & indxi, indxj ! compressed indices for cells with ice melting integer (kind=int_kind) :: i,j,ij,icells real (kind=dbl_kind) :: & hi , & ! ice thickness (m) hs , & ! snow depth (m) dTs , & ! surface temperature diff for freeze-up (C) Tp , & ! pond freezing temperature (C) apondn, & hpondn real (kind=dbl_kind), parameter :: & Td = c2 , & ! temperature difference for freeze-up (C) rexp = p01 , & ! pond contraction scaling dpthhi = 0.9_dbl_kind ! ratio of pond depth to ice thickness !----------------------------------------------------------------- ! Initialize !----------------------------------------------------------------- volpn(:,:) = hpnd(:,:) * apnd(:,:) * aicen(:,:) !----------------------------------------------------------------- ! Identify grid cells where ice can melt !----------------------------------------------------------------- icells = 0 do j = jlo, jhi do i = ilo, ihi if (aicen(i,j) > puny) then icells = icells + 1 indxi(icells) = i indxj(icells) = j endif enddo ! i enddo ! j do ij = 1, icells i = indxi(ij) j = indxj(ij) hi = vicen(i,j)/aicen(i,j) hs = vsnon(i,j)/aicen(i,j) if (hi < hi_min) then !-------------------------------------------------------------- ! Remove ponds on thin ice !-------------------------------------------------------------- apondn = c0 hpondn = c0 volpn (i,j) = c0 else !----------------------------------------------------------- ! Update pond volume !----------------------------------------------------------- volpn(i,j) = volpn(i,j) & + rfrac(i,j)/rhofresh*(meltt(i,j)*rhoi & + melts(i,j)*rhos & + frain(i,j)* dt)& * aicen(i,j) !----------------------------------------------------------- ! Shrink pond volume under freezing conditions !----------------------------------------------------------- Tp = Timelt - Td dTs = max(Tp - Tsfcn(i,j),c0) volpn(i,j) = volpn(i,j) * exp(rexp*dTs/Tp) volpn(i,j) = max(volpn(i,j), c0) ! fraction of ice covered by ponds apondn = min (sqrt(volpn(i,j)/(pndaspect*aicen(i,j))), c1) hpondn = pndaspect * apondn ! fraction of grid cell covered by ponds apondn = apondn * aicen(i,j) !----------------------------------------------------------- ! Limit pond depth !----------------------------------------------------------- hpondn = min(hpondn, dpthhi*hi) endif !----------------------------------------------------------- ! Reload tracer array !----------------------------------------------------------- apnd(i,j) = apondn / aicen(i,j) hpnd(i,j) = hpondn enddo end subroutine compute_ponds_cesm !======================================================================= ! ! Dumps all values needed for restarting ! ! authors Elizabeth C. Hunke, LANL ! David A. Bailey, NCAR subroutine write_restart_pond_cesm() use ice_domain_size, only: ncat use ice_fileunits, only: nu_dump_pond use ice_state, only: trcrn, nt_apnd, nt_hpnd use ice_restart, only: write_restart_field ! local variables logical (kind=log_kind) :: diag diag = .true. call write_restart_field(nu_dump_pond,0,trcrn(:,:,nt_apnd,:,:),'ruf8', & 'apnd',ncat,diag) call write_restart_field(nu_dump_pond,0,trcrn(:,:,nt_hpnd,:,:),'ruf8', & 'hpnd',ncat,diag) end subroutine write_restart_pond_cesm !======================================================================= ! Reads all values needed for a meltpond volume restart ! ! authors Elizabeth C. Hunke, LANL ! David A. Bailey, NCAR subroutine read_restart_pond_cesm() use ice_domain_size, only: ncat use ice_communicate, only: my_task, master_task use ice_fileunits, only: nu_diag, nu_restart_pond use ice_state, only: trcrn, nt_apnd, nt_hpnd use ice_restart, only: read_restart_field ! local variables logical (kind=log_kind) :: & diag diag = .true. if (my_task == master_task) write(nu_diag,*) 'min/max cesm ponds' call read_restart_field(nu_restart_pond,0,trcrn(:,:,nt_apnd,:,:),'ruf8', & 'apnd',ncat,diag,field_loc_center,field_type_scalar) call read_restart_field(nu_restart_pond,0,trcrn(:,:,nt_hpnd,:,:),'ruf8', & 'hpnd',ncat,diag,field_loc_center,field_type_scalar) end subroutine read_restart_pond_cesm !======================================================================= end module ice_meltpond_cesm !=======================================================================