| 1 | MODULE albedo |
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| 2 | !!====================================================================== |
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| 3 | !! *** MODULE albedo *** |
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| 4 | !! Ocean forcing: bulk thermohaline forcing of the ocean (or ice) |
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| 5 | !!===================================================================== |
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| 6 | !! History : 8.0 ! 2001-04 (LIM 1.0) |
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| 7 | !! NEMO 1.0 ! 2003-07 (C. Ethe, G. Madec) Optimization (old name:shine) |
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| 8 | !! - ! 2004-11 (C. Talandier) add albedo_init |
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| 9 | !! - ! 2001-06 (M. Vancoppenolle) LIM 3.0 |
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| 10 | !! - ! 2006-08 (G. Madec) cleaning for surface module |
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| 11 | !! 3.6 ! 2016-01 (C. Rousset) new parameterization for sea ice albedo |
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| 12 | !!---------------------------------------------------------------------- |
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| 13 | |
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| 14 | !!---------------------------------------------------------------------- |
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| 15 | !! albedo_ice : albedo for ice (clear and overcast skies) |
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| 16 | !! albedo_oce : albedo for ocean (clear and overcast skies) |
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| 17 | !! albedo_init : initialisation of albedo computation |
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| 18 | !!---------------------------------------------------------------------- |
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| 19 | USE phycst ! physical constants |
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| 20 | USE in_out_manager ! I/O manager |
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| 21 | USE lib_mpp ! MPP library |
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| 22 | USE wrk_nemo ! work arrays |
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| 23 | USE lib_fortran ! Fortran utilities (allows no signed zero when 'key_nosignedzero' defined) |
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| 24 | |
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| 25 | IMPLICIT NONE |
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| 26 | PRIVATE |
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| 27 | |
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| 28 | PUBLIC albedo_ice ! routine called sbcice_lim.F90 |
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| 29 | PUBLIC albedo_oce ! routine called by ??? |
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| 30 | |
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| 31 | INTEGER :: albd_init = 0 !: control flag for initialization |
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| 32 | |
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| 33 | REAL(wp) :: rmue = 0.40 ! cosine of local solar altitude |
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| 34 | REAL(wp) :: ralb_oce = 0.066 ! ocean or lead albedo (Pegau and Paulson, Ann. Glac. 2001) |
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| 35 | REAL(wp) :: c1 = 0.05 ! snow thickness (only for nn_ice_alb=0) |
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| 36 | REAL(wp) :: c2 = 0.10 ! " " |
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| 37 | REAL(wp) :: rcloud = 0.06 ! cloud effect on albedo (only-for nn_ice_alb=0) |
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| 38 | |
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| 39 | ! !!* namelist namsbc_alb |
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| 40 | INTEGER :: nn_ice_alb |
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| 41 | REAL(wp) :: rn_albice |
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| 42 | |
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| 43 | !!---------------------------------------------------------------------- |
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| 44 | !! NEMO/OPA 3.3 , NEMO Consortium (2010) |
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| 45 | !! $Id$ |
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| 46 | !! Software governed by the CeCILL licence (NEMOGCM/NEMO_CeCILL.txt) |
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| 47 | !!---------------------------------------------------------------------- |
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| 48 | CONTAINS |
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| 49 | |
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| 50 | SUBROUTINE albedo_ice( pt_ice, ph_ice, ph_snw, pa_ice_cs, pa_ice_os ) |
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| 51 | !!---------------------------------------------------------------------- |
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| 52 | !! *** ROUTINE albedo_ice *** |
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| 53 | !! |
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| 54 | !! ** Purpose : Computation of the albedo of the snow/ice system |
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| 55 | !! |
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| 56 | !! ** Method : Two schemes are available (from namelist parameter nn_ice_alb) |
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| 57 | !! 0: the scheme is that of Shine & Henderson-Sellers (JGR 1985) for clear-skies |
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| 58 | !! 1: the scheme is "home made" (for cloudy skies) and based on Brandt et al. (J. Climate 2005) |
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| 59 | !! and Grenfell & Perovich (JGR 2004) |
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| 60 | !! Description of scheme 1: |
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| 61 | !! 1) Albedo dependency on ice thickness follows the findings from Brandt et al (2005) |
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| 62 | !! which are an update of Allison et al. (JGR 1993) ; Brandt et al. 1999 |
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| 63 | !! 0-5cm : linear function of ice thickness |
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| 64 | !! 5-150cm: log function of ice thickness |
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| 65 | !! > 150cm: constant |
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| 66 | !! 2) Albedo dependency on snow thickness follows the findings from Grenfell & Perovich (2004) |
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| 67 | !! i.e. it increases as -EXP(-snw_thick/0.02) during freezing and -EXP(-snw_thick/0.03) during melting |
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| 68 | !! 3) Albedo dependency on clouds is speculated from measurements of Grenfell and Perovich (2004) |
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| 69 | !! i.e. cloudy-clear albedo depend on cloudy albedo following a 2d order polynomial law |
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| 70 | !! 4) The needed 4 parameters are: dry and melting snow, freezing ice and bare puddled ice |
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| 71 | !! |
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| 72 | !! ** Note : The parameterization from Shine & Henderson-Sellers presents several misconstructions: |
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| 73 | !! 1) ice albedo when ice thick. tends to 0 is different than ocean albedo |
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| 74 | !! 2) for small ice thick. covered with some snow (<3cm?), albedo is larger |
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| 75 | !! under melting conditions than under freezing conditions |
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| 76 | !! 3) the evolution of ice albedo as a function of ice thickness shows |
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| 77 | !! 3 sharp inflexion points (at 5cm, 100cm and 150cm) that look highly unrealistic |
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| 78 | !! |
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| 79 | !! References : Shine & Henderson-Sellers 1985, JGR, 90(D1), 2243-2250. |
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| 80 | !! Brandt et al. 2005, J. Climate, vol 18 |
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| 81 | !! Grenfell & Perovich 2004, JGR, vol 109 |
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| 82 | !!---------------------------------------------------------------------- |
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| 83 | REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: pt_ice ! ice surface temperature (Kelvin) |
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| 84 | REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_ice ! sea-ice thickness |
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| 85 | REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_snw ! snow thickness |
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| 86 | REAL(wp), INTENT( out), DIMENSION(:,:,:) :: pa_ice_cs ! albedo of ice under clear sky |
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| 87 | REAL(wp), INTENT( out), DIMENSION(:,:,:) :: pa_ice_os ! albedo of ice under overcast sky |
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| 88 | !! |
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| 89 | INTEGER :: ji, jj, jl ! dummy loop indices |
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| 90 | INTEGER :: ijpl ! number of ice categories (3rd dim of ice input arrays) |
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| 91 | REAL(wp) :: ralb_im, ralb_sf, ralb_sm, ralb_if |
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| 92 | REAL(wp) :: zswitch, z1_c1, z1_c2 |
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| 93 | REAL(wp) :: zalb_sm, zalb_sf, zalb_st ! albedo of snow melting, freezing, total |
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| 94 | REAL(wp), POINTER, DIMENSION(:,:,:) :: zalb, zalb_it ! intermediate variable & albedo of ice (snow free) |
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| 95 | !!--------------------------------------------------------------------- |
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| 96 | |
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| 97 | ijpl = SIZE( pt_ice, 3 ) ! number of ice categories |
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| 98 | |
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| 99 | CALL wrk_alloc( jpi,jpj,ijpl, zalb, zalb_it ) |
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| 100 | |
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| 101 | IF( albd_init == 0 ) CALL albedo_init ! initialization |
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| 102 | |
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| 103 | |
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| 104 | SELECT CASE ( nn_ice_alb ) |
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| 105 | |
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| 106 | !------------------------------------------ |
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| 107 | ! Shine and Henderson-Sellers (1985) |
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| 108 | !------------------------------------------ |
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| 109 | CASE( 0 ) |
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| 110 | |
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| 111 | ralb_sf = 0.80 ! dry snow |
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| 112 | ralb_sm = 0.65 ! melting snow |
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| 113 | ralb_if = 0.72 ! bare frozen ice |
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| 114 | ralb_im = rn_albice ! bare puddled ice |
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| 115 | |
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| 116 | ! Computation of ice albedo (free of snow) |
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| 117 | !$OMP PARALLEL DO schedule(static) private(jl,jj,ji) |
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| 118 | DO jl = 1, ijpl |
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| 119 | DO jj = 1, jpj |
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| 120 | DO ji = 1, jpi |
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| 121 | IF ( ph_snw(ji,jj,jl) == 0._wp .AND. pt_ice(ji,jj,jl) >= rt0_ice ) THEN |
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| 122 | zalb(ji,jj,jl) = ralb_im |
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| 123 | ELSE |
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| 124 | zalb(ji,jj,jl) = ralb_if |
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| 125 | END IF |
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| 126 | END DO |
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| 127 | END DO |
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| 128 | END DO |
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| 129 | |
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| 130 | WHERE ( 1.5 < ph_ice ) ; zalb_it = zalb |
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| 131 | ELSE WHERE( 1.0 < ph_ice .AND. ph_ice <= 1.5 ) ; zalb_it = 0.472 + 2.0 * ( zalb - 0.472 ) * ( ph_ice - 1.0 ) |
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| 132 | ELSE WHERE( 0.05 < ph_ice .AND. ph_ice <= 1.0 ) ; zalb_it = 0.2467 + 0.7049 * ph_ice & |
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| 133 | & - 0.8608 * ph_ice * ph_ice & |
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| 134 | & + 0.3812 * ph_ice * ph_ice * ph_ice |
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| 135 | ELSE WHERE ; zalb_it = 0.1 + 3.6 * ph_ice |
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| 136 | END WHERE |
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| 137 | !$OMP PARALLEL |
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| 138 | !$OMP DO schedule(static) private(jl, jj, ji,zswitch,zalb_sf,zalb_sm,zalb_st) |
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| 139 | DO jl = 1, ijpl |
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| 140 | DO jj = 1, jpj |
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| 141 | DO ji = 1, jpi |
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| 142 | ! freezing snow |
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| 143 | ! no effect of underlying ice layer IF snow thickness > c1. Albedo does not depend on snow thick if > c2 |
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| 144 | ! ! freezing snow |
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| 145 | zswitch = 1._wp - MAX( 0._wp , SIGN( 1._wp , - ( ph_snw(ji,jj,jl) - c1 ) ) ) |
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| 146 | zalb_sf = ( 1._wp - zswitch ) * ( zalb_it(ji,jj,jl) & |
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| 147 | & + ph_snw(ji,jj,jl) * ( ralb_sf - zalb_it(ji,jj,jl) ) / c1 ) & |
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| 148 | & + zswitch * ralb_sf |
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| 149 | |
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| 150 | ! melting snow |
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| 151 | ! no effect of underlying ice layer. Albedo does not depend on snow thick IF > c2 |
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| 152 | zswitch = MAX( 0._wp , SIGN( 1._wp , ph_snw(ji,jj,jl) - c2 ) ) |
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| 153 | zalb_sm = ( 1._wp - zswitch ) * ( ralb_im + ph_snw(ji,jj,jl) * ( ralb_sm - ralb_im ) / c2 ) & |
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| 154 | & + zswitch * ralb_sm |
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| 155 | ! |
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| 156 | ! snow albedo |
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| 157 | zswitch = MAX( 0._wp , SIGN( 1._wp , pt_ice(ji,jj,jl) - rt0_snow ) ) |
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| 158 | zalb_st = zswitch * zalb_sm + ( 1._wp - zswitch ) * zalb_sf |
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| 159 | |
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| 160 | ! Ice/snow albedo |
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| 161 | zswitch = 1._wp - MAX( 0._wp , SIGN( 1._wp , - ph_snw(ji,jj,jl) ) ) |
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| 162 | pa_ice_cs(ji,jj,jl) = zswitch * zalb_st + ( 1._wp - zswitch ) * zalb_it(ji,jj,jl) |
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| 163 | ! |
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| 164 | END DO |
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| 165 | END DO |
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| 166 | END DO |
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| 167 | |
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| 168 | !$OMP DO schedule(static) private(jl, jj, ji) |
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| 169 | DO jl = 1, ijpl |
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| 170 | DO jj = 1, jpj |
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| 171 | DO ji = 1, jpi |
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| 172 | pa_ice_os(ji,jj,jl) = pa_ice_cs(ji,jj,jl) + rcloud ! Oberhuber correction for overcast sky |
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| 173 | END DO |
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| 174 | END DO |
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| 175 | END DO |
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| 176 | !$OMP END PARALLEL |
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| 177 | |
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| 178 | !------------------------------------------ |
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| 179 | ! New parameterization (2016) |
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| 180 | !------------------------------------------ |
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| 181 | CASE( 1 ) |
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| 182 | |
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| 183 | ralb_im = rn_albice ! bare puddled ice |
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| 184 | ! compilation of values from literature |
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| 185 | ralb_sf = 0.85 ! dry snow |
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| 186 | ralb_sm = 0.75 ! melting snow |
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| 187 | ralb_if = 0.60 ! bare frozen ice |
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| 188 | ! Perovich et al 2002 (Sheba) => the only dataset for which all types of ice/snow were retrieved |
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| 189 | ! ralb_sf = 0.85 ! dry snow |
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| 190 | ! ralb_sm = 0.72 ! melting snow |
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| 191 | ! ralb_if = 0.65 ! bare frozen ice |
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| 192 | ! Brandt et al 2005 (East Antarctica) |
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| 193 | ! ralb_sf = 0.87 ! dry snow |
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| 194 | ! ralb_sm = 0.82 ! melting snow |
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| 195 | ! ralb_if = 0.54 ! bare frozen ice |
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| 196 | ! |
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| 197 | ! Computation of ice albedo (free of snow) |
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| 198 | z1_c1 = 1. / ( LOG(1.5) - LOG(0.05) ) |
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| 199 | z1_c2 = 1. / 0.05 |
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| 200 | WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0_ice ) ; zalb = ralb_im |
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| 201 | ELSE WHERE ; zalb = ralb_if |
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| 202 | END WHERE |
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| 203 | |
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| 204 | WHERE ( 1.5 < ph_ice ) ; zalb_it = zalb |
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| 205 | ELSE WHERE( 0.05 < ph_ice .AND. ph_ice <= 1.5 ) ; zalb_it = zalb + ( 0.18 - zalb ) * z1_c1 * & |
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| 206 | & ( LOG(1.5) - LOG(ph_ice) ) |
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| 207 | ELSE WHERE ; zalb_it = ralb_oce + ( 0.18 - ralb_oce ) * z1_c2 * ph_ice |
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| 208 | END WHERE |
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| 209 | |
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| 210 | z1_c1 = 1. / 0.02 |
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| 211 | z1_c2 = 1. / 0.03 |
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| 212 | ! Computation of the snow/ice albedo |
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| 213 | !$OMP PARALLEL DO schedule(static) private(jl, jj, ji,zswitch,zalb_sf,zalb_sm,zalb_st) |
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| 214 | DO jl = 1, ijpl |
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| 215 | DO jj = 1, jpj |
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| 216 | DO ji = 1, jpi |
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| 217 | zalb_sf = ralb_sf - ( ralb_sf - zalb_it(ji,jj,jl)) * EXP( - ph_snw(ji,jj,jl) * z1_c1 ); |
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| 218 | zalb_sm = ralb_sm - ( ralb_sm - zalb_it(ji,jj,jl)) * EXP( - ph_snw(ji,jj,jl) * z1_c2 ); |
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| 219 | |
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| 220 | ! snow albedo |
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| 221 | zswitch = MAX( 0._wp , SIGN( 1._wp , pt_ice(ji,jj,jl) - rt0_snow ) ) |
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| 222 | zalb_st = zswitch * zalb_sm + ( 1._wp - zswitch ) * zalb_sf |
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| 223 | |
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| 224 | ! Ice/snow albedo |
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| 225 | zswitch = MAX( 0._wp , SIGN( 1._wp , - ph_snw(ji,jj,jl) ) ) |
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| 226 | pa_ice_os(ji,jj,jl) = ( 1._wp - zswitch ) * zalb_st + zswitch * zalb_it(ji,jj,jl) |
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| 227 | |
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| 228 | END DO |
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| 229 | END DO |
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| 230 | END DO |
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| 231 | ! Effect of the clouds (2d order polynomial) |
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| 232 | pa_ice_cs = pa_ice_os - ( - 0.1010 * pa_ice_os * pa_ice_os + 0.1933 * pa_ice_os - 0.0148 ); |
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| 233 | |
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| 234 | END SELECT |
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| 235 | |
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| 236 | CALL wrk_dealloc( jpi,jpj,ijpl, zalb, zalb_it ) |
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| 237 | ! |
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| 238 | END SUBROUTINE albedo_ice |
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| 239 | |
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| 240 | |
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| 241 | SUBROUTINE albedo_oce( pa_oce_os , pa_oce_cs ) |
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| 242 | !!---------------------------------------------------------------------- |
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| 243 | !! *** ROUTINE albedo_oce *** |
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| 244 | !! |
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| 245 | !! ** Purpose : Computation of the albedo of the ocean |
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| 246 | !!---------------------------------------------------------------------- |
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| 247 | REAL(wp), DIMENSION(:,:), INTENT(out) :: pa_oce_os ! albedo of ocean under overcast sky |
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| 248 | REAL(wp), DIMENSION(:,:), INTENT(out) :: pa_oce_cs ! albedo of ocean under clear sky |
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| 249 | !! |
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| 250 | REAL(wp) :: zcoef |
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| 251 | INTEGER :: ji, jj ! dummy loop indices |
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| 252 | !!---------------------------------------------------------------------- |
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| 253 | ! |
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| 254 | zcoef = 0.05 / ( 1.1 * rmue**1.4 + 0.15 ) ! Parameterization of Briegled and Ramanathan, 1982 |
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| 255 | !$OMP PARALLEL DO schedule(static) private(jj, ji) |
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| 256 | DO jj = 1, jpj |
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| 257 | DO ji = 1, jpi |
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| 258 | pa_oce_cs(ji,jj) = zcoef |
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| 259 | pa_oce_os(ji,jj) = 0.06 ! Parameterization of Kondratyev, 1969 and Payne, 1972 |
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| 260 | END DO |
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| 261 | END DO |
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| 262 | ! |
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| 263 | END SUBROUTINE albedo_oce |
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| 264 | |
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| 265 | |
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| 266 | SUBROUTINE albedo_init |
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| 267 | !!---------------------------------------------------------------------- |
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| 268 | !! *** ROUTINE albedo_init *** |
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| 269 | !! |
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| 270 | !! ** Purpose : initializations for the albedo parameters |
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| 271 | !! |
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| 272 | !! ** Method : Read the namelist namsbc_alb |
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| 273 | !!---------------------------------------------------------------------- |
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| 274 | INTEGER :: ios ! Local integer output status for namelist read |
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| 275 | NAMELIST/namsbc_alb/ nn_ice_alb, rn_albice |
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| 276 | !!---------------------------------------------------------------------- |
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| 277 | ! |
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| 278 | albd_init = 1 ! indicate that the initialization has been done |
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| 279 | ! |
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| 280 | REWIND( numnam_ref ) ! Namelist namsbc_alb in reference namelist : Albedo parameters |
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| 281 | READ ( numnam_ref, namsbc_alb, IOSTAT = ios, ERR = 901) |
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| 282 | 901 IF( ios /= 0 ) CALL ctl_nam ( ios , 'namsbc_alb in reference namelist', lwp ) |
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| 283 | |
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| 284 | REWIND( numnam_cfg ) ! Namelist namsbc_alb in configuration namelist : Albedo parameters |
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| 285 | READ ( numnam_cfg, namsbc_alb, IOSTAT = ios, ERR = 902 ) |
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| 286 | 902 IF( ios /= 0 ) CALL ctl_nam ( ios , 'namsbc_alb in configuration namelist', lwp ) |
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| 287 | IF(lwm) WRITE ( numond, namsbc_alb ) |
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| 288 | ! |
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| 289 | IF(lwp) THEN ! Control print |
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| 290 | WRITE(numout,*) |
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| 291 | WRITE(numout,*) 'albedo : set albedo parameters' |
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| 292 | WRITE(numout,*) '~~~~~~~' |
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| 293 | WRITE(numout,*) ' Namelist namsbc_alb : albedo ' |
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| 294 | WRITE(numout,*) ' choose the albedo parameterization nn_ice_alb = ', nn_ice_alb |
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| 295 | WRITE(numout,*) ' albedo of bare puddled ice rn_albice = ', rn_albice |
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| 296 | ENDIF |
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| 297 | ! |
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| 298 | END SUBROUTINE albedo_init |
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| 299 | |
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| 300 | !!====================================================================== |
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| 301 | END MODULE albedo |
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