Changeset 9987 for branches/UKMO/dev_r5518_obs_oper_update_icethick/NEMOGCM/NEMO/OPA_SRC/SBC/albedo.F90
- Timestamp:
- 2018-07-23T11:33:03+02:00 (6 years ago)
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branches/UKMO/dev_r5518_obs_oper_update_icethick/NEMOGCM/NEMO/OPA_SRC/SBC/albedo.F90
r7960 r9987 9 9 !! - ! 2001-06 (M. Vancoppenolle) LIM 3.0 10 10 !! - ! 2006-08 (G. Madec) cleaning for surface module 11 !! 3.6 ! 2016-01 (C. Rousset) new parameterization for sea ice albedo 11 12 !!---------------------------------------------------------------------- 12 13 … … 29 30 30 31 INTEGER :: albd_init = 0 !: control flag for initialization 31 REAL(wp) :: zzero = 0.e0 ! constant values32 REAL(wp) :: zone = 1.e0 ! " "33 34 REAL(wp) :: c1 = 0.05 ! constants values35 REAL(wp) :: c2 = 0.10 !" "36 REAL(wp) :: r mue = 0.40 ! cosine of local solar altitude37 32 33 REAL(wp) :: rmue = 0.40 ! cosine of local solar altitude 34 REAL(wp) :: ralb_oce = 0.066 ! ocean or lead albedo (Pegau and Paulson, Ann. Glac. 2001) 35 REAL(wp) :: c1 = 0.05 ! snow thickness (only for nn_ice_alb=0) 36 REAL(wp) :: c2 = 0.10 ! " " 37 REAL(wp) :: rcloud = 0.06 ! cloud effect on albedo (only-for nn_ice_alb=0) 38 38 39 ! !!* namelist namsbc_alb 39 REAL(wp) :: rn_cloud ! cloudiness effect on snow or ice albedo (Grenfell & Perovich, 1984) 40 #if defined key_lim3 41 REAL(wp) :: rn_albice ! albedo of melting ice in the arctic and antarctic (Shine & Hendersson-Sellers) 42 #else 43 REAL(wp) :: rn_albice ! albedo of melting ice in the arctic and antarctic (Shine & Hendersson-Sellers) 44 #endif 45 REAL(wp) :: rn_alphd ! coefficients for linear interpolation used to compute 46 REAL(wp) :: rn_alphdi ! albedo between two extremes values (Pyane, 1972) 47 REAL(wp) :: rn_alphc ! 40 INTEGER :: nn_ice_alb 41 REAL(wp) :: rn_albice 48 42 49 43 !!---------------------------------------------------------------------- … … 59 53 !! 60 54 !! ** Purpose : Computation of the albedo of the snow/ice system 61 !! as well as the ocean one62 55 !! 63 !! ** Method : - Computation of the albedo of snow or ice (choose the 64 !! rignt one by a large number of tests 65 !! - Computation of the albedo of the ocean 66 !! 67 !! References : Shine and Hendersson-Sellers 1985, JGR, 90(D1), 2243-2250. 56 !! ** Method : Two schemes are available (from namelist parameter nn_ice_alb) 57 !! 0: the scheme is that of Shine & Henderson-Sellers (JGR 1985) for clear-skies 58 !! 1: the scheme is "home made" (for cloudy skies) and based on Brandt et al. (J. Climate 2005) 59 !! and Grenfell & Perovich (JGR 2004) 60 !! Description of scheme 1: 61 !! 1) Albedo dependency on ice thickness follows the findings from Brandt et al (2005) 62 !! which are an update of Allison et al. (JGR 1993) ; Brandt et al. 1999 63 !! 0-5cm : linear function of ice thickness 64 !! 5-150cm: log function of ice thickness 65 !! > 150cm: constant 66 !! 2) Albedo dependency on snow thickness follows the findings from Grenfell & Perovich (2004) 67 !! i.e. it increases as -EXP(-snw_thick/0.02) during freezing and -EXP(-snw_thick/0.03) during melting 68 !! 3) Albedo dependency on clouds is speculated from measurements of Grenfell and Perovich (2004) 69 !! i.e. cloudy-clear albedo depend on cloudy albedo following a 2d order polynomial law 70 !! 4) The needed 4 parameters are: dry and melting snow, freezing ice and bare puddled ice 71 !! 72 !! ** Note : The parameterization from Shine & Henderson-Sellers presents several misconstructions: 73 !! 1) ice albedo when ice thick. tends to 0 is different than ocean albedo 74 !! 2) for small ice thick. covered with some snow (<3cm?), albedo is larger 75 !! under melting conditions than under freezing conditions 76 !! 3) the evolution of ice albedo as a function of ice thickness shows 77 !! 3 sharp inflexion points (at 5cm, 100cm and 150cm) that look highly unrealistic 78 !! 79 !! References : Shine & Henderson-Sellers 1985, JGR, 90(D1), 2243-2250. 80 !! Brandt et al. 2005, J. Climate, vol 18 81 !! Grenfell & Perovich 2004, JGR, vol 109 68 82 !!---------------------------------------------------------------------- 69 83 REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: pt_ice ! ice surface temperature (Kelvin) … … 73 87 REAL(wp), INTENT( out), DIMENSION(:,:,:) :: pa_ice_os ! albedo of ice under overcast sky 74 88 !! 75 INTEGER :: ji, jj, jl ! dummy loop indices 76 INTEGER :: ijpl ! number of ice categories (3rd dim of ice input arrays) 77 REAL(wp) :: zalbpsnm ! albedo of ice under clear sky when snow is melting 78 REAL(wp) :: zalbpsnf ! albedo of ice under clear sky when snow is freezing 79 REAL(wp) :: zalbpsn ! albedo of snow/ice system when ice is coverd by snow 80 REAL(wp) :: zalbpic ! albedo of snow/ice system when ice is free of snow 81 REAL(wp) :: zithsn ! = 1 for hsn >= 0 ( ice is cov. by snow ) ; = 0 otherwise (ice is free of snow) 82 REAL(wp) :: zitmlsn ! = 1 freezinz snow (pt_ice >=rt0_snow) ; = 0 melting snow (pt_ice<rt0_snow) 83 REAL(wp) :: zihsc1 ! = 1 hsn <= c1 ; = 0 hsn > c1 84 REAL(wp) :: zihsc2 ! = 1 hsn >= c2 ; = 0 hsn < c2 85 !! 86 REAL(wp), POINTER, DIMENSION(:,:,:) :: zalbfz ! = rn_alphdi for freezing ice ; = rn_albice for melting ice 87 REAL(wp), POINTER, DIMENSION(:,:,:) :: zficeth ! function of ice thickness 89 INTEGER :: ji, jj, jl ! dummy loop indices 90 INTEGER :: ijpl ! number of ice categories (3rd dim of ice input arrays) 91 REAL(wp) :: ralb_im, ralb_sf, ralb_sm, ralb_if 92 REAL(wp) :: zswitch, z1_c1, z1_c2 93 REAL(wp) :: zalb_sm, zalb_sf, zalb_st ! albedo of snow melting, freezing, total 94 REAL(wp), POINTER, DIMENSION(:,:,:) :: zalb, zalb_it ! intermediate variable & albedo of ice (snow free) 88 95 !!--------------------------------------------------------------------- 89 96 90 97 ijpl = SIZE( pt_ice, 3 ) ! number of ice categories 91 92 CALL wrk_alloc( jpi,jpj,ijpl, zalb fz, zficeth)98 99 CALL wrk_alloc( jpi,jpj,ijpl, zalb, zalb_it ) 93 100 94 101 IF( albd_init == 0 ) CALL albedo_init ! initialization 95 102 96 !--------------------------- 97 ! Computation of zficeth 98 !--------------------------- 99 ! ice free of snow and melts 100 WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0_ice ) ; zalbfz(:,:,:) = rn_albice 101 ELSE WHERE ; zalbfz(:,:,:) = rn_alphdi 102 END WHERE 103 104 WHERE ( 1.5 < ph_ice ) ; zficeth = zalbfz 105 ELSE WHERE( 1.0 < ph_ice .AND. ph_ice <= 1.5 ) ; zficeth = 0.472 + 2.0 * ( zalbfz - 0.472 ) * ( ph_ice - 1.0 ) 106 ELSE WHERE( 0.05 < ph_ice .AND. ph_ice <= 1.0 ) ; zficeth = 0.2467 + 0.7049 * ph_ice & 107 & - 0.8608 * ph_ice * ph_ice & 108 & + 0.3812 * ph_ice * ph_ice * ph_ice 109 ELSE WHERE ; zficeth = 0.1 + 3.6 * ph_ice 110 END WHERE 111 112 !!gm old code 113 ! DO jl = 1, ijpl 114 ! DO jj = 1, jpj 115 ! DO ji = 1, jpi 116 ! IF( ph_ice(ji,jj,jl) > 1.5 ) THEN 117 ! zficeth(ji,jj,jl) = zalbfz(ji,jj,jl) 118 ! ELSEIF( ph_ice(ji,jj,jl) > 1.0 .AND. ph_ice(ji,jj,jl) <= 1.5 ) THEN 119 ! zficeth(ji,jj,jl) = 0.472 + 2.0 * ( zalbfz(ji,jj,jl) - 0.472 ) * ( ph_ice(ji,jj,jl) - 1.0 ) 120 ! ELSEIF( ph_ice(ji,jj,jl) > 0.05 .AND. ph_ice(ji,jj,jl) <= 1.0 ) THEN 121 ! zficeth(ji,jj,jl) = 0.2467 + 0.7049 * ph_ice(ji,jj,jl) & 122 ! & - 0.8608 * ph_ice(ji,jj,jl) * ph_ice(ji,jj,jl) & 123 ! & + 0.3812 * ph_ice(ji,jj,jl) * ph_ice(ji,jj,jl) * ph_ice (ji,jj,jl) 124 ! ELSE 125 ! zficeth(ji,jj,jl) = 0.1 + 3.6 * ph_ice(ji,jj,jl) 126 ! ENDIF 127 ! END DO 128 ! END DO 129 ! END DO 130 !!gm end old code 131 132 !----------------------------------------------- 133 ! Computation of the snow/ice albedo system 134 !-------------------------- --------------------- 135 136 ! Albedo of snow-ice for clear sky. 137 !----------------------------------------------- 138 DO jl = 1, ijpl 139 DO jj = 1, jpj 140 DO ji = 1, jpi 141 ! Case of ice covered by snow. 142 ! ! freezing snow 143 zihsc1 = 1.0 - MAX( zzero , SIGN( zone , - ( ph_snw(ji,jj,jl) - c1 ) ) ) 144 zalbpsnf = ( 1.0 - zihsc1 ) * ( zficeth(ji,jj,jl) & 145 & + ph_snw(ji,jj,jl) * ( rn_alphd - zficeth(ji,jj,jl) ) / c1 ) & 146 & + zihsc1 * rn_alphd 147 ! ! melting snow 148 zihsc2 = MAX( zzero , SIGN( zone , ph_snw(ji,jj,jl) - c2 ) ) 149 zalbpsnm = ( 1.0 - zihsc2 ) * ( rn_albice + ph_snw(ji,jj,jl) * ( rn_alphc - rn_albice ) / c2 ) & 150 & + zihsc2 * rn_alphc 151 ! 152 zitmlsn = MAX( zzero , SIGN( zone , pt_ice(ji,jj,jl) - rt0_snow ) ) 153 zalbpsn = zitmlsn * zalbpsnm + ( 1.0 - zitmlsn ) * zalbpsnf 154 155 ! Case of ice free of snow. 156 zalbpic = zficeth(ji,jj,jl) 157 158 ! albedo of the system 159 zithsn = 1.0 - MAX( zzero , SIGN( zone , - ph_snw(ji,jj,jl) ) ) 160 pa_ice_cs(ji,jj,jl) = zithsn * zalbpsn + ( 1.0 - zithsn ) * zalbpic 103 104 SELECT CASE ( nn_ice_alb ) 105 106 !------------------------------------------ 107 ! Shine and Henderson-Sellers (1985) 108 !------------------------------------------ 109 CASE( 0 ) 110 111 ralb_sf = 0.80 ! dry snow 112 ralb_sm = 0.65 ! melting snow 113 ralb_if = 0.72 ! bare frozen ice 114 ralb_im = rn_albice ! bare puddled ice 115 116 ! Computation of ice albedo (free of snow) 117 WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0_ice ) ; zalb(:,:,:) = ralb_im 118 ELSE WHERE ; zalb(:,:,:) = ralb_if 119 END WHERE 120 121 WHERE ( 1.5 < ph_ice ) ; zalb_it = zalb 122 ELSE WHERE( 1.0 < ph_ice .AND. ph_ice <= 1.5 ) ; zalb_it = 0.472 + 2.0 * ( zalb - 0.472 ) * ( ph_ice - 1.0 ) 123 ELSE WHERE( 0.05 < ph_ice .AND. ph_ice <= 1.0 ) ; zalb_it = 0.2467 + 0.7049 * ph_ice & 124 & - 0.8608 * ph_ice * ph_ice & 125 & + 0.3812 * ph_ice * ph_ice * ph_ice 126 ELSE WHERE ; zalb_it = 0.1 + 3.6 * ph_ice 127 END WHERE 128 129 DO jl = 1, ijpl 130 DO jj = 1, jpj 131 DO ji = 1, jpi 132 ! freezing snow 133 ! no effect of underlying ice layer IF snow thickness > c1. Albedo does not depend on snow thick if > c2 134 ! ! freezing snow 135 zswitch = 1._wp - MAX( 0._wp , SIGN( 1._wp , - ( ph_snw(ji,jj,jl) - c1 ) ) ) 136 zalb_sf = ( 1._wp - zswitch ) * ( zalb_it(ji,jj,jl) & 137 & + ph_snw(ji,jj,jl) * ( ralb_sf - zalb_it(ji,jj,jl) ) / c1 ) & 138 & + zswitch * ralb_sf 139 140 ! melting snow 141 ! no effect of underlying ice layer. Albedo does not depend on snow thick IF > c2 142 zswitch = MAX( 0._wp , SIGN( 1._wp , ph_snw(ji,jj,jl) - c2 ) ) 143 zalb_sm = ( 1._wp - zswitch ) * ( ralb_im + ph_snw(ji,jj,jl) * ( ralb_sm - ralb_im ) / c2 ) & 144 & + zswitch * ralb_sm 145 ! 146 ! snow albedo 147 zswitch = MAX( 0._wp , SIGN( 1._wp , pt_ice(ji,jj,jl) - rt0_snow ) ) 148 zalb_st = zswitch * zalb_sm + ( 1._wp - zswitch ) * zalb_sf 149 150 ! Ice/snow albedo 151 zswitch = 1._wp - MAX( 0._wp , SIGN( 1._wp , - ph_snw(ji,jj,jl) ) ) 152 pa_ice_cs(ji,jj,jl) = zswitch * zalb_st + ( 1._wp - zswitch ) * zalb_it(ji,jj,jl) 153 ! 154 END DO 161 155 END DO 162 156 END DO 163 END DO 164 165 ! Albedo of snow-ice for overcast sky. 166 !---------------------------------------------- 167 pa_ice_os(:,:,:) = pa_ice_cs(:,:,:) + rn_cloud ! Oberhuber correction 168 ! 169 CALL wrk_dealloc( jpi,jpj,ijpl, zalbfz, zficeth ) 157 158 pa_ice_os(:,:,:) = pa_ice_cs(:,:,:) + rcloud ! Oberhuber correction for overcast sky 159 160 !------------------------------------------ 161 ! New parameterization (2016) 162 !------------------------------------------ 163 CASE( 1 ) 164 165 ralb_im = rn_albice ! bare puddled ice 166 ! compilation of values from literature 167 ralb_sf = 0.85 ! dry snow 168 ralb_sm = 0.75 ! melting snow 169 ralb_if = 0.60 ! bare frozen ice 170 ! Perovich et al 2002 (Sheba) => the only dataset for which all types of ice/snow were retrieved 171 ! ralb_sf = 0.85 ! dry snow 172 ! ralb_sm = 0.72 ! melting snow 173 ! ralb_if = 0.65 ! bare frozen ice 174 ! Brandt et al 2005 (East Antarctica) 175 ! ralb_sf = 0.87 ! dry snow 176 ! ralb_sm = 0.82 ! melting snow 177 ! ralb_if = 0.54 ! bare frozen ice 178 ! 179 ! Computation of ice albedo (free of snow) 180 z1_c1 = 1. / ( LOG(1.5) - LOG(0.05) ) 181 z1_c2 = 1. / 0.05 182 WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0_ice ) ; zalb = ralb_im 183 ELSE WHERE ; zalb = ralb_if 184 END WHERE 185 186 WHERE ( 1.5 < ph_ice ) ; zalb_it = zalb 187 ELSE WHERE( 0.05 < ph_ice .AND. ph_ice <= 1.5 ) ; zalb_it = zalb + ( 0.18 - zalb ) * z1_c1 * & 188 & ( LOG(1.5) - LOG(ph_ice) ) 189 ELSE WHERE ; zalb_it = ralb_oce + ( 0.18 - ralb_oce ) * z1_c2 * ph_ice 190 END WHERE 191 192 z1_c1 = 1. / 0.02 193 z1_c2 = 1. / 0.03 194 ! Computation of the snow/ice albedo 195 DO jl = 1, ijpl 196 DO jj = 1, jpj 197 DO ji = 1, jpi 198 zalb_sf = ralb_sf - ( ralb_sf - zalb_it(ji,jj,jl)) * EXP( - ph_snw(ji,jj,jl) * z1_c1 ); 199 zalb_sm = ralb_sm - ( ralb_sm - zalb_it(ji,jj,jl)) * EXP( - ph_snw(ji,jj,jl) * z1_c2 ); 200 201 ! snow albedo 202 zswitch = MAX( 0._wp , SIGN( 1._wp , pt_ice(ji,jj,jl) - rt0_snow ) ) 203 zalb_st = zswitch * zalb_sm + ( 1._wp - zswitch ) * zalb_sf 204 205 ! Ice/snow albedo 206 zswitch = MAX( 0._wp , SIGN( 1._wp , - ph_snw(ji,jj,jl) ) ) 207 pa_ice_os(ji,jj,jl) = ( 1._wp - zswitch ) * zalb_st + zswitch * zalb_it(ji,jj,jl) 208 209 END DO 210 END DO 211 END DO 212 ! Effect of the clouds (2d order polynomial) 213 pa_ice_cs = pa_ice_os - ( - 0.1010 * pa_ice_os * pa_ice_os + 0.1933 * pa_ice_os - 0.0148 ); 214 215 END SELECT 216 217 CALL wrk_dealloc( jpi,jpj,ijpl, zalb, zalb_it ) 170 218 ! 171 219 END SUBROUTINE albedo_ice … … 181 229 REAL(wp), DIMENSION(:,:), INTENT(out) :: pa_oce_cs ! albedo of ocean under clear sky 182 230 !! 183 REAL(wp) :: zcoef ! local scalar184 !!---------------------------------------------------------------------- 185 ! 186 zcoef = 0.05 / ( 1.1 * rmue**1.4 + 0.15 ) ! Parameterization of Briegled and Ramanathan, 1982187 pa_oce_cs(:,:) = zcoef 188 pa_oce_os(:,:) = 0.06! Parameterization of Kondratyev, 1969 and Payne, 1972231 REAL(wp) :: zcoef 232 !!---------------------------------------------------------------------- 233 ! 234 zcoef = 0.05 / ( 1.1 * rmue**1.4 + 0.15 ) ! Parameterization of Briegled and Ramanathan, 1982 235 pa_oce_cs(:,:) = zcoef 236 pa_oce_os(:,:) = 0.06 ! Parameterization of Kondratyev, 1969 and Payne, 1972 189 237 ! 190 238 END SUBROUTINE albedo_oce … … 200 248 !!---------------------------------------------------------------------- 201 249 INTEGER :: ios ! Local integer output status for namelist read 202 NAMELIST/namsbc_alb/ rn_cloud, rn_albice, rn_alphd, rn_alphdi, rn_alphc250 NAMELIST/namsbc_alb/ nn_ice_alb, rn_albice 203 251 !!---------------------------------------------------------------------- 204 252 ! … … 219 267 WRITE(numout,*) '~~~~~~~' 220 268 WRITE(numout,*) ' Namelist namsbc_alb : albedo ' 221 WRITE(numout,*) ' correction for snow and ice albedo rn_cloud = ', rn_cloud 222 WRITE(numout,*) ' albedo of melting ice in the arctic and antarctic rn_albice = ', rn_albice 223 WRITE(numout,*) ' coefficients for linear rn_alphd = ', rn_alphd 224 WRITE(numout,*) ' interpolation used to compute albedo rn_alphdi = ', rn_alphdi 225 WRITE(numout,*) ' between two extremes values (Pyane, 1972) rn_alphc = ', rn_alphc 269 WRITE(numout,*) ' choose the albedo parameterization nn_ice_alb = ', nn_ice_alb 270 WRITE(numout,*) ' albedo of bare puddled ice rn_albice = ', rn_albice 226 271 ENDIF 227 272 !
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