MODULE albedo
!!======================================================================
!! *** MODULE albedo ***
!! Ocean forcing: bulk thermohaline forcing of the ocean (or ice)
!!=====================================================================
!! History : 8.0 ! 2001-04 (LIM 1.0)
!! NEMO 1.0 ! 2003-07 (C. Ethe, G. Madec) Optimization (old name:shine)
!! - ! 2004-11 (C. Talandier) add albedo_init
!! - ! 2001-06 (M. Vancoppenolle) LIM 3.0
!! - ! 2006-08 (G. Madec) cleaning for surface module
!! 3.6 ! 2016-01 (C. Rousset) new parameterization for sea ice albedo
!!----------------------------------------------------------------------
!!----------------------------------------------------------------------
!! albedo_ice : albedo for ice (clear and overcast skies)
!! albedo_oce : albedo for ocean (clear and overcast skies)
!! albedo_init : initialisation of albedo computation
!!----------------------------------------------------------------------
USE phycst ! physical constants
USE in_out_manager ! I/O manager
USE lib_mpp ! MPP library
USE wrk_nemo ! work arrays
USE lib_fortran ! Fortran utilities (allows no signed zero when 'key_nosignedzero' defined)
IMPLICIT NONE
PRIVATE
PUBLIC albedo_ice ! routine called sbcice_lim.F90
PUBLIC albedo_oce ! routine called by ???
INTEGER :: albd_init = 0 !: control flag for initialization
REAL(wp) :: rmue = 0.40 ! cosine of local solar altitude
REAL(wp) :: ralb_oce = 0.066 ! ocean or lead albedo (Pegau and Paulson, Ann. Glac. 2001)
REAL(wp) :: c1 = 0.05 ! snow thickness (only for nn_ice_alb=0)
REAL(wp) :: c2 = 0.10 ! " "
REAL(wp) :: rcloud = 0.06 ! cloud effect on albedo (only-for nn_ice_alb=0)
! !!* namelist namsbc_alb
INTEGER :: nn_ice_alb
REAL(wp) :: rn_alb_sdry, rn_alb_smlt, rn_alb_idry, rn_alb_imlt
!!----------------------------------------------------------------------
!! NEMO/OPA 3.3 , NEMO Consortium (2010)
!! $Id: albedo.F90 7596 2017-01-20 17:50:18Z clem $
!! Software governed by the CeCILL licence (NEMOGCM/NEMO_CeCILL.txt)
!!----------------------------------------------------------------------
CONTAINS
SUBROUTINE albedo_ice( pt_ice, ph_ice, ph_snw, pa_ice_cs, pa_ice_os )
!!----------------------------------------------------------------------
!! *** ROUTINE albedo_ice ***
!!
!! ** Purpose : Computation of the albedo of the snow/ice system
!!
!! ** Method : Two schemes are available (from namelist parameter nn_ice_alb)
!! 0: the scheme is that of Shine & Henderson-Sellers (JGR 1985) for clear-skies
!! 1: the scheme is "home made" (for cloudy skies) and based on Brandt et al. (J. Climate 2005)
!! and Grenfell & Perovich (JGR 2004)
!! Description of scheme 1:
!! 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
!!
!! ** Note : The parameterization from Shine & Henderson-Sellers presents 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_ice ! ice surface temperature (Kelvin)
REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_ice ! sea-ice thickness
REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_snw ! snow thickness
REAL(wp), INTENT( out), DIMENSION(:,:,:) :: pa_ice_cs ! albedo of ice under clear sky
REAL(wp), INTENT( out), DIMENSION(:,:,:) :: pa_ice_os ! albedo of ice under overcast sky
!!
INTEGER :: ji, jj, jl ! dummy loop indices
INTEGER :: ijpl ! number of ice categories (3rd dim of ice input arrays)
REAL(wp) :: ralb_im, ralb_sf, ralb_sm, ralb_if
REAL(wp) :: zswitch, z1_c1, z1_c2
REAL(wp) :: zalb_sm, zalb_sf, zalb_st ! albedo of snow melting, freezing, total
REAL(wp), POINTER, DIMENSION(:,:,:) :: zalb, zalb_it ! intermediate variable & albedo of ice (snow free)
!!---------------------------------------------------------------------
ijpl = SIZE( pt_ice, 3 ) ! number of ice categories
CALL wrk_alloc( jpi,jpj,ijpl, zalb, zalb_it )
IF( albd_init == 0 ) CALL albedo_init ! initialization
ralb_sf = rn_alb_sdry ! dry snow
ralb_sm = rn_alb_smlt ! melting snow
ralb_if = rn_alb_idry ! bare frozen ice
ralb_im = rn_alb_imlt ! bare puddled ice
SELECT CASE ( nn_ice_alb )
!------------------------------------------
! Shine and Henderson-Sellers (1985)
!------------------------------------------
CASE( 0 )
!ralb_sf = 0.80 ! dry snow
!ralb_sm = 0.65 ! melting snow
!ralb_if = 0.72 ! bare frozen ice
!ralb_im = ... ! bare puddled ice
! Computation of ice albedo (free of snow)
WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0_ice ) ; zalb(:,:,:) = ralb_im
ELSE WHERE ; zalb(:,:,:) = ralb_if
END WHERE
WHERE ( 1.5 < ph_ice ) ; zalb_it = zalb
ELSE WHERE( 1.0 < ph_ice .AND. ph_ice <= 1.5 ) ; zalb_it = 0.472 + 2.0 * ( zalb - 0.472 ) * ( ph_ice - 1.0 )
ELSE WHERE( 0.05 < ph_ice .AND. ph_ice <= 1.0 ) ; zalb_it = 0.2467 + 0.7049 * ph_ice &
& - 0.8608 * ph_ice * ph_ice &
& + 0.3812 * ph_ice * ph_ice * ph_ice
ELSE WHERE ; zalb_it = 0.1 + 3.6 * ph_ice
END WHERE
DO jl = 1, ijpl
DO jj = 1, jpj
DO ji = 1, jpi
! freezing snow
! no effect of underlying ice layer IF snow thickness > c1. Albedo does not depend on snow thick if > c2
! ! freezing snow
zswitch = 1._wp - MAX( 0._wp , SIGN( 1._wp , - ( ph_snw(ji,jj,jl) - c1 ) ) )
zalb_sf = ( 1._wp - zswitch ) * ( zalb_it(ji,jj,jl) &
& + ph_snw(ji,jj,jl) * ( ralb_sf - zalb_it(ji,jj,jl) ) / c1 ) &
& + zswitch * ralb_sf
! melting snow
! no effect of underlying ice layer. Albedo does not depend on snow thick IF > c2
zswitch = MAX( 0._wp , SIGN( 1._wp , ph_snw(ji,jj,jl) - c2 ) )
zalb_sm = ( 1._wp - zswitch ) * ( ralb_im + ph_snw(ji,jj,jl) * ( ralb_sm - ralb_im ) / c2 ) &
& + zswitch * ralb_sm
!
! snow albedo
zswitch = MAX( 0._wp , SIGN( 1._wp , pt_ice(ji,jj,jl) - rt0_snow ) )
zalb_st = zswitch * zalb_sm + ( 1._wp - zswitch ) * zalb_sf
! Ice/snow albedo
zswitch = 1._wp - MAX( 0._wp , SIGN( 1._wp , - ph_snw(ji,jj,jl) ) )
pa_ice_cs(ji,jj,jl) = zswitch * zalb_st + ( 1._wp - zswitch ) * zalb_it(ji,jj,jl)
!
END DO
END DO
END DO
pa_ice_os(:,:,:) = pa_ice_cs(:,:,:) + rcloud ! Oberhuber correction for overcast sky
!------------------------------------------
! New parameterization (2016)
!------------------------------------------
CASE( 1 )
! ralb_im = ... ! bare puddled ice
! compilation of values from literature
! ralb_sf = 0.85 ! dry snow
! ralb_sm = 0.75 ! melting snow
! ralb_if = 0.60 ! bare frozen ice
! Perovich et al 2002 (Sheba) => the only dataset for which all types of ice/snow were retrieved
! ralb_sf = 0.85 ! dry snow
! ralb_sm = 0.72 ! melting snow
! ralb_if = 0.65 ! bare frozen ice
! Brandt et al 2005 (East Antarctica)
! ralb_sf = 0.87 ! dry snow
! ralb_sm = 0.82 ! melting snow
! ralb_if = 0.54 ! bare frozen ice
!
! Computation of ice albedo (free of snow)
z1_c1 = 1. / ( LOG(1.5) - LOG(0.05) )
z1_c2 = 1. / 0.05
WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0_ice ) ; zalb = ralb_im
ELSE WHERE ; zalb = ralb_if
END WHERE
WHERE ( 1.5 < ph_ice ) ; zalb_it = zalb
ELSE WHERE( 0.05 < ph_ice .AND. ph_ice <= 1.5 ) ; zalb_it = zalb + ( 0.18 - zalb ) * z1_c1 * &
& ( LOG(1.5) - LOG(ph_ice) )
ELSE WHERE ; zalb_it = ralb_oce + ( 0.18 - ralb_oce ) * z1_c2 * ph_ice
END WHERE
z1_c1 = 1. / 0.02
z1_c2 = 1. / 0.03
! Computation of the snow/ice albedo
DO jl = 1, ijpl
DO jj = 1, jpj
DO ji = 1, jpi
zalb_sf = ralb_sf - ( ralb_sf - zalb_it(ji,jj,jl)) * EXP( - ph_snw(ji,jj,jl) * z1_c1 );
zalb_sm = ralb_sm - ( ralb_sm - zalb_it(ji,jj,jl)) * EXP( - ph_snw(ji,jj,jl) * z1_c2 );
! snow albedo
zswitch = MAX( 0._wp , SIGN( 1._wp , pt_ice(ji,jj,jl) - rt0_snow ) )
zalb_st = zswitch * zalb_sm + ( 1._wp - zswitch ) * zalb_sf
! Ice/snow albedo
zswitch = MAX( 0._wp , SIGN( 1._wp , - ph_snw(ji,jj,jl) ) )
pa_ice_os(ji,jj,jl) = ( 1._wp - zswitch ) * zalb_st + zswitch * zalb_it(ji,jj,jl)
END DO
END DO
END DO
! Effect of the clouds (2d order polynomial)
pa_ice_cs = pa_ice_os - ( - 0.1010 * pa_ice_os * pa_ice_os + 0.1933 * pa_ice_os - 0.0148 );
END SELECT
CALL wrk_dealloc( jpi,jpj,ijpl, zalb, zalb_it )
!
END SUBROUTINE albedo_ice
SUBROUTINE albedo_oce( pa_oce_os , pa_oce_cs )
!!----------------------------------------------------------------------
!! *** ROUTINE albedo_oce ***
!!
!! ** Purpose : Computation of the albedo of the ocean
!!----------------------------------------------------------------------
REAL(wp), DIMENSION(:,:), INTENT(out) :: pa_oce_os ! albedo of ocean under overcast sky
REAL(wp), DIMENSION(:,:), INTENT(out) :: pa_oce_cs ! albedo of ocean under clear sky
!!
REAL(wp) :: zcoef
!!----------------------------------------------------------------------
!
zcoef = 0.05 / ( 1.1 * rmue**1.4 + 0.15 ) ! Parameterization of Briegled and Ramanathan, 1982
pa_oce_cs(:,:) = zcoef
pa_oce_os(:,:) = 0.06 ! Parameterization of Kondratyev, 1969 and Payne, 1972
!
END SUBROUTINE albedo_oce
SUBROUTINE albedo_init
!!----------------------------------------------------------------------
!! *** ROUTINE albedo_init ***
!!
!! ** Purpose : initializations for the albedo parameters
!!
!! ** Method : Read the namelist namsbc_alb
!!----------------------------------------------------------------------
INTEGER :: ios ! Local integer output status for namelist read
NAMELIST/namsbc_alb/ nn_ice_alb, rn_alb_sdry, rn_alb_smlt, rn_alb_idry , rn_alb_imlt
!!----------------------------------------------------------------------
!
albd_init = 1 ! indicate that the initialization has been done
!
REWIND( numnam_ref ) ! Namelist namsbc_alb in reference namelist : Albedo parameters
READ ( numnam_ref, namsbc_alb, IOSTAT = ios, ERR = 901)
901 IF( ios /= 0 ) CALL ctl_nam ( ios , 'namsbc_alb in reference namelist', lwp )
REWIND( numnam_cfg ) ! Namelist namsbc_alb in configuration namelist : Albedo parameters
READ ( numnam_cfg, namsbc_alb, IOSTAT = ios, ERR = 902 )
902 IF( ios /= 0 ) CALL ctl_nam ( ios , 'namsbc_alb in configuration namelist', lwp )
IF(lwm) WRITE ( numond, namsbc_alb )
!
IF(lwp) THEN ! Control print
WRITE(numout,*)
WRITE(numout,*) 'albedo : set albedo parameters'
WRITE(numout,*) '~~~~~~~'
WRITE(numout,*) ' Namelist namsbc_alb : albedo '
WRITE(numout,*) ' choose the albedo parameterization nn_ice_alb = ', nn_ice_alb
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
ENDIF
!
END SUBROUTINE albedo_init
!!======================================================================
END MODULE albedo