MODULE icealb !!====================================================================== !! *** MODULE icealb *** !! Atmospheric forcing: Albedo over sea ice !!===================================================================== !! History : 4.0 ! 2017-07 (C. Rousset) Split ice and ocean albedos !! 4.0 ! 2018 (many people) SI3 [aka Sea Ice cube] !!---------------------------------------------------------------------- #if defined key_si3 !!---------------------------------------------------------------------- !! 'key_si3' SI3 sea-ice model !!---------------------------------------------------------------------- !! ice_alb : albedo for ice (clear and overcast skies) !! ice_alb_init : initialisation of albedo computation !!---------------------------------------------------------------------- USE ice, ONLY: jpl ! sea-ice: number of categories USE phycst ! physical constants USE dom_oce ! domain: ocean ! USE in_out_manager ! I/O manager USE lib_mpp ! MPP library USE lib_fortran ! Fortran utilities (allows no signed zero when 'key_nosignedzero' defined) USE timing ! Timing IMPLICIT NONE PRIVATE PUBLIC ice_alb_init ! called in icestp PUBLIC ice_alb ! called in icesbc.F90 and iceupdate.F90 REAL(wp), PUBLIC, PARAMETER :: rn_alb_oce = 0.066 !: ocean or lead albedo (Pegau and Paulson, Ann. Glac. 2001) ! ! !!* albedo namelist (namalb) REAL(wp) :: rn_alb_sdry ! dry snow albedo REAL(wp) :: rn_alb_smlt ! melting snow albedo REAL(wp) :: rn_alb_idry ! dry ice albedo REAL(wp) :: rn_alb_imlt ! bare puddled ice albedo REAL(wp) :: rn_alb_dpnd ! ponded ice albedo !! * Substitutions # include "do_loop_substitute.h90" !!---------------------------------------------------------------------- !! NEMO/ICE 4.0 , NEMO Consortium (2018) !! $Id$ !! Software governed by the CeCILL license (see ./LICENSE) !!---------------------------------------------------------------------- CONTAINS SUBROUTINE ice_alb( pt_su, ph_ice, ph_snw, ld_pnd_alb, pafrac_pnd, ph_pnd, palb_cs, palb_os ) !!---------------------------------------------------------------------- !! *** ROUTINE ice_alb *** !! !! ** Purpose : Computation of the albedo of the snow/ice system !! !! ** Method : The scheme is "home made" (for cloudy skies) and based on Brandt et al. (J. Climate 2005) !! and Grenfell & Perovich (JGR 2004) !! 1) Albedo dependency on ice thickness follows the findings from Brandt et al (2005) !! which are an update of Allison et al. (JGR 1993) ; Brandt et al. 1999 !! 0-5cm : linear function of ice thickness !! 5-150cm: log function of ice thickness !! > 150cm: constant !! 2) Albedo dependency on snow thickness follows the findings from Grenfell & Perovich (2004) !! i.e. it increases as -EXP(-snw_thick/0.02) during freezing and -EXP(-snw_thick/0.03) during melting !! 3) Albedo dependency on clouds is speculated from measurements of Grenfell and Perovich (2004) !! i.e. cloudy-clear albedo depend on cloudy albedo following a 2d order polynomial law !! 4) The needed 4 parameters are: dry and melting snow, freezing ice and bare puddled ice !! !! compilation of values from literature (reference overcast sky values) !! rn_alb_sdry = 0.85 ! dry snow !! rn_alb_smlt = 0.75 ! melting snow !! rn_alb_idry = 0.60 ! bare frozen ice !! rn_alb_imlt = 0.50 ! bare puddled ice albedo !! rn_alb_dpnd = 0.36 ! ponded-ice overcast albedo (Lecomte et al, 2015) !! ! early melt pnds 0.27, late melt ponds 0.14 Grenfell & Perovich !! Perovich et al 2002 (Sheba) => the only dataset for which all types of ice/snow were retrieved !! rn_alb_sdry = 0.85 ! dry snow !! rn_alb_smlt = 0.72 ! melting snow !! rn_alb_idry = 0.65 ! bare frozen ice !! Brandt et al 2005 (East Antarctica) !! rn_alb_sdry = 0.87 ! dry snow !! rn_alb_smlt = 0.82 ! melting snow !! rn_alb_idry = 0.54 ! bare frozen ice !! !! ** Note : The old parameterization from Shine & Henderson-Sellers (not here anymore) presented several misconstructions !! 1) ice albedo when ice thick. tends to 0 is different than ocean albedo !! 2) for small ice thick. covered with some snow (<3cm?), albedo is larger !! under melting conditions than under freezing conditions !! 3) the evolution of ice albedo as a function of ice thickness shows !! 3 sharp inflexion points (at 5cm, 100cm and 150cm) that look highly unrealistic !! !! References : Shine & Henderson-Sellers 1985, JGR, 90(D1), 2243-2250. !! Brandt et al. 2005, J. Climate, vol 18 !! Grenfell & Perovich 2004, JGR, vol 109 !!---------------------------------------------------------------------- REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: pt_su ! ice surface temperature (Kelvin) REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_ice ! sea-ice thickness REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_snw ! snow depth LOGICAL , INTENT(in ) :: ld_pnd_alb ! effect of melt ponds on albedo REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: pafrac_pnd ! melt pond relative fraction (per unit ice area) REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_pnd ! melt pond depth REAL(wp), INTENT( out), DIMENSION(:,:,:) :: palb_cs ! albedo of ice under clear sky REAL(wp), INTENT( out), DIMENSION(:,:,:) :: palb_os ! albedo of ice under overcast sky ! INTEGER :: ji, jj, jl ! dummy loop indices REAL(wp) :: z1_c1, z1_c2,z1_c3, z1_c4 ! local scalar REAL(wp) :: z1_href_pnd ! inverse of the characteristic length scale (Lecomte et al. 2015) REAL(wp) :: zalb_pnd, zafrac_pnd ! ponded sea ice albedo & relative pound fraction REAL(wp) :: zalb_ice, zafrac_ice ! bare sea ice albedo & relative ice fraction REAL(wp) :: zalb_snw, zafrac_snw ! snow-covered sea ice albedo & relative snow fraction !!--------------------------------------------------------------------- ! IF( ln_timing ) CALL timing_start('icealb') ! z1_href_pnd = 1. / 0.05 z1_c1 = 1. / ( LOG(1.5) - LOG(0.05) ) z1_c2 = 1. / 0.05 z1_c3 = 1. / 0.02 z1_c4 = 1. / 0.03 ! DO jl = 1, jpl DO_2D_11_11 ! !--- Specific snow, ice and pond fractions (for now, we prevent melt ponds and snow at the same time) IF( ph_snw(ji,jj,jl) == 0._wp ) THEN zafrac_snw = 0._wp IF( ld_pnd_alb ) THEN zafrac_pnd = pafrac_pnd(ji,jj,jl) ELSE zafrac_pnd = 0._wp ENDIF zafrac_ice = 1._wp - zafrac_pnd ELSE zafrac_snw = 1._wp ! Snow fully "shades" melt ponds and ice zafrac_pnd = 0._wp zafrac_ice = 0._wp ENDIF ! ! !--- Bare ice albedo (for hi > 150cm) IF( ld_pnd_alb ) THEN zalb_ice = rn_alb_idry ELSE IF( ph_snw(ji,jj,jl) == 0._wp .AND. pt_su(ji,jj,jl) >= rt0 ) THEN ; zalb_ice = rn_alb_imlt ELSE ; zalb_ice = rn_alb_idry ; ENDIF ENDIF ! !--- Bare ice albedo (for hi < 150cm) IF( 0.05 < ph_ice(ji,jj,jl) .AND. ph_ice(ji,jj,jl) <= 1.5 ) THEN ! 5cm < hi < 150cm zalb_ice = zalb_ice + ( 0.18 - zalb_ice ) * z1_c1 * ( LOG(1.5) - LOG(ph_ice(ji,jj,jl)) ) ELSEIF( ph_ice(ji,jj,jl) <= 0.05 ) THEN ! 0cm < hi < 5cm zalb_ice = rn_alb_oce + ( 0.18 - rn_alb_oce ) * z1_c2 * ph_ice(ji,jj,jl) ENDIF ! ! !--- Snow-covered ice albedo (freezing, melting cases) IF( pt_su(ji,jj,jl) < rt0 ) THEN zalb_snw = rn_alb_sdry - ( rn_alb_sdry - zalb_ice ) * EXP( - ph_snw(ji,jj,jl) * z1_c3 ) ELSE zalb_snw = rn_alb_smlt - ( rn_alb_smlt - zalb_ice ) * EXP( - ph_snw(ji,jj,jl) * z1_c4 ) ENDIF ! !--- Ponded ice albedo IF( ld_pnd_alb ) THEN zalb_pnd = rn_alb_dpnd - ( rn_alb_dpnd - zalb_ice ) * EXP( - ph_pnd(ji,jj,jl) * z1_href_pnd ) ELSE zalb_pnd = rn_alb_dpnd ENDIF ! !--- Surface albedo is weighted mean of snow, ponds and bare ice contributions palb_os(ji,jj,jl) = ( zafrac_snw * zalb_snw + zafrac_pnd * zalb_pnd + zafrac_ice * zalb_ice ) * tmask(ji,jj,1) ! palb_cs(ji,jj,jl) = palb_os(ji,jj,jl) & & - ( - 0.1010 * palb_os(ji,jj,jl) * palb_os(ji,jj,jl) & & + 0.1933 * palb_os(ji,jj,jl) - 0.0148 ) * tmask(ji,jj,1) ! END_2D END DO ! ! IF( ln_timing ) CALL timing_stop('icealb') ! END SUBROUTINE ice_alb SUBROUTINE ice_alb_init !!---------------------------------------------------------------------- !! *** ROUTINE alb_init *** !! !! ** Purpose : initializations for the albedo parameters !! !! ** Method : Read the namelist namalb !!---------------------------------------------------------------------- INTEGER :: ios ! Local integer output status for namelist read !! NAMELIST/namalb/ rn_alb_sdry, rn_alb_smlt, rn_alb_idry, rn_alb_imlt, rn_alb_dpnd !!---------------------------------------------------------------------- ! READ ( numnam_ice_ref, namalb, IOSTAT = ios, ERR = 901) 901 IF( ios /= 0 ) CALL ctl_nam ( ios , 'namalb in reference namelist' ) READ ( numnam_ice_cfg, namalb, IOSTAT = ios, ERR = 902 ) 902 IF( ios > 0 ) CALL ctl_nam ( ios , 'namalb in configuration namelist' ) IF(lwm) WRITE( numoni, namalb ) ! IF(lwp) THEN ! Control print WRITE(numout,*) WRITE(numout,*) 'ice_alb_init: set albedo parameters' WRITE(numout,*) '~~~~~~~~~~~~' WRITE(numout,*) ' Namelist namalb:' WRITE(numout,*) ' albedo of dry snow rn_alb_sdry = ', rn_alb_sdry WRITE(numout,*) ' albedo of melting snow rn_alb_smlt = ', rn_alb_smlt WRITE(numout,*) ' albedo of dry ice rn_alb_idry = ', rn_alb_idry WRITE(numout,*) ' albedo of bare puddled ice rn_alb_imlt = ', rn_alb_imlt WRITE(numout,*) ' albedo of ponded ice rn_alb_dpnd = ', rn_alb_dpnd ENDIF ! END SUBROUTINE ice_alb_init #else !!---------------------------------------------------------------------- !! Default option Dummy module NO SI3 sea-ice model !!---------------------------------------------------------------------- #endif !!====================================================================== END MODULE icealb