- Timestamp:
- 2017-10-18T19:14:32+02:00 (7 years ago)
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branches/2017/dev_r7881_ENHANCE09_RK3/NEMOGCM/NEMO/LIM_SRC_3/icealb.F90
r8586 r8637 35 35 REAL(wp) , PARAMETER :: pp1_c2 = 1. / ppc2 36 36 ! 37 ! ** albedo namelist (namalb) 38 INTEGER :: nn_ice_alb ! type of albedo scheme: 0: Shine & Henderson-Sellers (JGR 1985) 39 ! ! 1: "home made" based on Brandt et al. (JClim 2005) 40 ! ! and Grenfell & Perovich (JGR 2004) 41 ! ! 2: Same as 1 but with melt ponds 37 ! !!* albedo namelist (namalb) 42 38 REAL(wp) :: rn_alb_sdry ! dry snow albedo 43 39 REAL(wp) :: rn_alb_smlt ! melting snow albedo … … 53 49 CONTAINS 54 50 55 SUBROUTINE ice_alb( pt_ ice, ph_ice, ph_snw, pafrac_pnd, ph_pnd, ld_pnd, pa_ice_cs, pa_ice_os )51 SUBROUTINE ice_alb( pt_su, ph_ice, ph_snw, ld_pnd_alb, pafrac_pnd, ph_pnd, palb_cs, palb_os ) 56 52 !!---------------------------------------------------------------------- 57 53 !! *** ROUTINE ice_alb *** … … 59 55 !! ** Purpose : Computation of the albedo of the snow/ice system 60 56 !! 61 !! ** Method : Two schemes are available (from namelist parameter nn_ice_alb) 62 !! 0: the scheme is that of Shine & Henderson-Sellers (JGR 1985) for clear-skies 63 !! 1: the scheme is "home made" (for cloudy skies) and based on Brandt et al. (J. Climate 2005) 64 !! and Grenfell & Perovich (JGR 2004) 65 !! 2: fractional surface-based formulation of scheme 1 (NEW) 66 !! Description of scheme 1: 57 !! ** Method : The scheme is "home made" (for cloudy skies) and based on Brandt et al. (J. Climate 2005) 58 !! and Grenfell & Perovich (JGR 2004) 67 59 !! 1) Albedo dependency on ice thickness follows the findings from Brandt et al (2005) 68 60 !! which are an update of Allison et al. (JGR 1993) ; Brandt et al. 1999 … … 76 68 !! 4) The needed 4 parameters are: dry and melting snow, freezing ice and bare puddled ice 77 69 !! 78 !! ** Note : The parameterization from Shine & Henderson-Sellers presents several misconstructions: 70 !! compilation of values from literature (reference overcast sky values) 71 !! rn_alb_sdry = 0.85 ! dry snow 72 !! rn_alb_smlt = 0.75 ! melting snow 73 !! rn_alb_idry = 0.60 ! bare frozen ice 74 !! rn_alb_imlt = 0.50 ! bare puddled ice albedo 75 !! rn_alb_dpnd = 0.36 ! ponded-ice overcast albedo (Lecomte et al, 2015) 76 !! ! early melt pnds 0.27, late melt ponds 0.14 Grenfell & Perovich 77 !! Perovich et al 2002 (Sheba) => the only dataset for which all types of ice/snow were retrieved 78 !! rn_alb_sdry = 0.85 ! dry snow 79 !! rn_alb_smlt = 0.72 ! melting snow 80 !! rn_alb_idry = 0.65 ! bare frozen ice 81 !! Brandt et al 2005 (East Antarctica) 82 !! rn_alb_sdry = 0.87 ! dry snow 83 !! rn_alb_smlt = 0.82 ! melting snow 84 !! rn_alb_idry = 0.54 ! bare frozen ice 85 !! 86 !! ** Note : The old parameterization from Shine & Henderson-Sellers (not here anymore) presented several misconstructions 79 87 !! 1) ice albedo when ice thick. tends to 0 is different than ocean albedo 80 88 !! 2) for small ice thick. covered with some snow (<3cm?), albedo is larger … … 87 95 !! Grenfell & Perovich 2004, JGR, vol 109 88 96 !!---------------------------------------------------------------------- 89 REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: pt_ ice! ice surface temperature (Kelvin)97 REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: pt_su ! ice surface temperature (Kelvin) 90 98 REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_ice ! sea-ice thickness 91 99 REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_snw ! snow depth 100 LOGICAL , INTENT(in ) :: ld_pnd_alb ! effect of melt ponds on albedo 92 101 REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: pafrac_pnd ! melt pond relative fraction (per unit ice area) 93 102 REAL(wp), INTENT(in ), DIMENSION(:,:,:) :: ph_pnd ! melt pond depth 94 LOGICAL , INTENT(in ) :: ld_pnd ! melt ponds radiatively active or not 95 REAL(wp), INTENT( out), DIMENSION(:,:,:) :: pa_ice_cs ! albedo of ice under clear sky 96 REAL(wp), INTENT( out), DIMENSION(:,:,:) :: pa_ice_os ! albedo of ice under overcast sky 103 REAL(wp), INTENT( out), DIMENSION(:,:,:) :: palb_cs ! albedo of ice under clear sky 104 REAL(wp), INTENT( out), DIMENSION(:,:,:) :: palb_os ! albedo of ice under overcast sky 97 105 ! 98 106 INTEGER :: ji, jj, jl ! dummy loop indices 99 REAL(wp) :: zswitch, z1_c1, z1_c2 ! local scalar 100 REAL(wp) :: z1_href_pnd ! - - 101 REAL(wp) :: zalb_sm, zalb_sf, zalb_st ! albedo of snow melting, freezing, total 102 ! 103 REAL(wp), DIMENSION(jpi,jpj,jpl) :: zalb, zalb_it ! intermediate variable & albedo of ice (snow free) 104 !! MV MP 105 REAL(wp), DIMENSION(jpi,jpj,jpl) :: zalb_pnd ! ponded sea ice albedo 106 REAL(wp), DIMENSION(jpi,jpj,jpl) :: zalb_ice ! bare sea ice albedo 107 REAL(wp), DIMENSION(jpi,jpj,jpl) :: zalb_snw ! snow-covered sea ice albedo 108 REAL(wp), DIMENSION(jpi,jpj,jpl) :: zafrac_snw ! relative snow fraction 109 REAL(wp), DIMENSION(jpi,jpj,jpl) :: zafrac_ice ! relative ice fraction 110 REAL(wp), DIMENSION(jpi,jpj,jpl) :: zafrac_pnd ! relative ice fraction (effective) 107 REAL(wp) :: z1_c1, z1_c2,z1_c3, z1_c4 ! local scalar 108 REAL(wp) :: z1_href_pnd ! inverse of the characteristic length scale (Lecomte et al. 2015) 109 REAL(wp) :: zalb_pnd, zafrac_pnd ! ponded sea ice albedo & relative pound fraction 110 REAL(wp) :: zalb_ice, zafrac_ice ! bare sea ice albedo & relative ice fraction 111 REAL(wp) :: zalb_snw, zafrac_snw ! snow-covered sea ice albedo & relative snow fraction 111 112 !!--------------------------------------------------------------------- 112 113 ! 113 114 IF( nn_timing == 1 ) CALL timing_start('icealb') 114 115 ! 115 !----------------------------------------------------- 116 ! Snow-free albedo (no ice thickness dependence yet) 117 !----------------------------------------------------- 118 ! 119 ! Part common to nn_ice_alb = 0, 1, 2 120 ! 121 IF ( .NOT. ld_pnd ) THEN !--- No melt ponds OR radiatively inactive melt ponds 122 ! Bare ice albedo is prescribed, with implicit assumption on pond fraction and depth 123 WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0 ) ; zalb(:,:,:) = rn_alb_imlt 124 ELSEWHERE ; zalb(:,:,:) = rn_alb_idry 125 END WHERE 126 ENDIF 127 128 SELECT CASE ( nn_ice_alb ) ! select a parameterization 129 ! 130 ! !------------------------------------------ 131 CASE( 0 ) ! Shine and Henderson-Sellers (1985) ! (based on clear sky values) 132 ! !------------------------------------------ 133 ! 134 ! ! Thickness-dependent bare ice albedo 135 WHERE ( 1.5 < ph_ice ) ; zalb_it = zalb 136 ELSEWHERE( 1.0 < ph_ice .AND. ph_ice <= 1.5 ) ; zalb_it = 0.472 + 2.0 * ( zalb - 0.472 ) * ( ph_ice - 1.0 ) 137 ELSEWHERE( 0.05 < ph_ice .AND. ph_ice <= 1.0 ) ; zalb_it = 0.2467 + 0.7049 * ph_ice & 138 & - 0.8608 * ph_ice * ph_ice & 139 & + 0.3812 * ph_ice * ph_ice * ph_ice 140 ELSEWHERE ; zalb_it = 0.1 + 3.6 * ph_ice 141 END WHERE 142 ! 143 IF ( ld_pnd ) THEN ! Depth-dependent ponded ice albedo 144 z1_href_pnd = 1. / 0.05 ! inverse of the characteristic length scale (Lecomte et al. 2015) 145 zalb_pnd = rn_alb_dpnd - ( rn_alb_dpnd - zalb_it ) * EXP( - ph_pnd * z1_href_pnd ) 146 ! ! Snow-free ice albedo is a function of pond fraction 147 WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0 ) 148 zalb_it = zalb_it * ( 1. - pafrac_pnd ) + zalb_pnd * pafrac_pnd 149 END WHERE 150 ENDIF 151 ! 152 DO jl = 1, jpl 153 DO jj = 1, jpj 154 DO ji = 1, jpi 155 ! ! Freezing snow 156 ! no effect of underlying ice layer IF snow thickness > c1. Albedo does not depend on snow thick if > ppc2 157 zswitch = 1._wp - MAX( 0._wp , SIGN( 1._wp , - ( ph_snw(ji,jj,jl) - ppc1 ) ) ) 158 zalb_sf = ( 1._wp - zswitch ) * ( zalb_it(ji,jj,jl) & 159 & + ph_snw(ji,jj,jl) * ( rn_alb_sdry - zalb_it(ji,jj,jl) ) * pp1_c1 ) & 160 & + zswitch * rn_alb_sdry 161 ! 162 ! ! Melting snow 163 ! no effect of underlying ice layer. Albedo does not depend on snow thick IF > ppc2 164 zswitch = MAX( 0._wp , SIGN( 1._wp , ph_snw(ji,jj,jl) - ppc2 ) ) 165 zalb_sm = ( 1._wp - zswitch ) * ( rn_alb_imlt + ph_snw(ji,jj,jl) * ( rn_alb_smlt - rn_alb_imlt ) * pp1_c2 ) & 166 & + zswitch * rn_alb_smlt 167 ! 168 ! ! Snow albedo 169 zswitch = MAX( 0._wp , SIGN( 1._wp , pt_ice(ji,jj,jl) - rt0_snow ) ) 170 zalb_st = zswitch * zalb_sm + ( 1._wp - zswitch ) * zalb_sf 171 ! 172 ! ! Surface albedo 173 zswitch = 1._wp - MAX( 0._wp , SIGN( 1._wp , - ph_snw(ji,jj,jl) ) ) 174 pa_ice_cs(ji,jj,jl) = zswitch * zalb_st + ( 1._wp - zswitch ) * zalb_it(ji,jj,jl) 175 ! 176 END DO 116 z1_href_pnd = 0.05 117 z1_c1 = 1. / ( LOG(1.5) - LOG(0.05) ) 118 z1_c2 = 1. / 0.05 119 z1_c3 = 1. / 0.02 120 z1_c4 = 1. / 0.03 121 ! 122 DO jl = 1, jpl 123 DO jj = 1, jpj 124 DO ji = 1, jpi 125 ! !--- Specific snow, ice and pond fractions (for now, we prevent melt ponds and snow at the same time) 126 IF( ph_snw(ji,jj,jl) == 0._wp ) THEN 127 zafrac_snw = 0._wp 128 IF( ld_pnd_alb ) THEN 129 zafrac_pnd = pafrac_pnd(ji,jj,jl) 130 ELSE 131 zafrac_pnd = 0._wp 132 ENDIF 133 zafrac_ice = 1._wp - zafrac_pnd 134 ELSE 135 zafrac_snw = 1._wp ! Snow fully "shades" melt ponds and ice 136 zafrac_pnd = 0._wp 137 zafrac_ice = 0._wp 138 ENDIF 139 ! 140 ! !--- Bare ice albedo (for hi > 150cm) 141 IF( ld_pnd_alb ) THEN 142 zalb_ice = rn_alb_idry 143 ELSE 144 IF( ph_snw(ji,jj,jl) == 0._wp .AND. pt_su(ji,jj,jl) >= rt0 ) THEN ; zalb_ice = rn_alb_imlt 145 ELSE ; zalb_ice = rn_alb_idry ; ENDIF 146 ENDIF 147 ! !--- Bare ice albedo (for hi < 150cm) 148 IF( 0.05 < ph_ice(ji,jj,jl) .AND. ph_ice(ji,jj,jl) <= 1.5 ) THEN ! 5cm < hi < 150cm 149 zalb_ice = zalb_ice + ( 0.18 - zalb_ice ) * z1_c1 * ( LOG(1.5) - LOG(ph_ice(ji,jj,jl)) ) 150 ELSEIF( ph_ice(ji,jj,jl) <= 0.05 ) THEN ! 0cm < hi < 5cm 151 zalb_ice = rn_alb_oce + ( 0.18 - rn_alb_oce ) * z1_c2 * ph_ice(ji,jj,jl) 152 ENDIF 153 ! 154 ! !--- Snow-covered ice albedo (freezing, melting cases) 155 IF( pt_su(ji,jj,jl) < rt0_snow ) THEN 156 zalb_snw = rn_alb_sdry - ( rn_alb_sdry - zalb_ice ) * EXP( - ph_snw(ji,jj,jl) * z1_c3 ) 157 ELSE 158 zalb_snw = rn_alb_smlt - ( rn_alb_smlt - zalb_ice ) * EXP( - ph_snw(ji,jj,jl) * z1_c4 ) 159 ENDIF 160 ! !--- Ponded ice albedo 161 IF( ld_pnd_alb ) THEN 162 zalb_pnd = rn_alb_dpnd - ( rn_alb_dpnd - zalb_ice ) * EXP( - ph_pnd(ji,jj,jl) * z1_href_pnd ) 163 ELSE 164 zalb_pnd = rn_alb_dpnd 165 ENDIF 166 ! !--- Surface albedo is weighted mean of snow, ponds and bare ice contributions 167 palb_os(ji,jj,jl) = zafrac_snw * zalb_snw + zafrac_pnd * zalb_pnd + zafrac_ice * zalb_ice 168 ! 177 169 END DO 178 170 END DO 179 ! 180 pa_ice_os(:,:,:) = pa_ice_cs(:,:,:) + ppcloud ! Oberhuber correction for overcast sky 181 ! 182 ! 183 ! !------------------------------------------ 184 CASE( 1 ) ! New parameterization (2016) ! (based on overcast sky values) 185 ! !------------------------------------------ 186 ! 187 ! compilation of values from literature (reference overcast sky values) 188 ! rn_alb_sdry = 0.85 ! dry snow 189 ! rn_alb_smlt = 0.75 ! melting snow 190 ! rn_alb_idry = 0.60 ! bare frozen ice 191 ! rn_alb_dpnd = 0.36 ! ponded-ice overcast albedo (Lecomte et al, 2015) 192 ! ! early melt pnds 0.27, late melt ponds 0.14 Grenfell & Perovich 193 ! Perovich et al 2002 (Sheba) => the only dataset for which all types of ice/snow were retrieved 194 ! rn_alb_sdry = 0.85 ! dry snow 195 ! rn_alb_smlt = 0.72 ! melting snow 196 ! rn_alb_idry = 0.65 ! bare frozen ice 197 ! Brandt et al 2005 (East Antarctica) 198 ! rn_alb_sdry = 0.87 ! dry snow 199 ! rn_alb_smlt = 0.82 ! melting snow 200 ! rn_alb_idry = 0.54 ! bare frozen ice 201 ! 202 ! !--- Computation of snow-free ice albedo 203 z1_c1 = 1. / ( LOG(1.5) - LOG(0.05) ) 204 z1_c2 = 1. / 0.05 205 206 ! !--- Accounting for the ice-thickness dependency 207 WHERE ( 1.5 < ph_ice ) ; zalb_it = zalb 208 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) ) 209 ELSE WHERE ; zalb_it = rn_alb_oce + ( 0.18 - rn_alb_oce ) * z1_c2 * ph_ice 210 END WHERE 211 ! 212 IF ( ld_pnd ) THEN ! Depth-dependent ponded ice albedo 213 z1_href_pnd = 0.05 ! inverse of the characteristic length scale (Lecomte et al. 2015) 214 zalb_pnd = rn_alb_dpnd - ( rn_alb_dpnd - zalb_it ) * EXP( - ph_pnd * z1_href_pnd ) 215 ! 216 ! ! Snow-free ice albedo is weighted mean of ponded ice and bare ice contributions 217 WHERE ( ph_snw == 0._wp .AND. pt_ice >= rt0 ) 218 zalb_it = zalb_it * ( 1. - pafrac_pnd ) + zalb_pnd * pafrac_pnd 219 END WHERE 220 ENDIF 221 ! 222 ! !--- Overcast sky surface albedo (accounting for snow, ice melt ponds) 223 z1_c1 = 1. / 0.02 224 z1_c2 = 1. / 0.03 225 DO jl = 1, jpl 226 DO jj = 1, jpj 227 DO ji = 1, jpi 228 ! Snow depth dependence of snow albedo 229 zalb_sf = rn_alb_sdry - ( rn_alb_sdry - zalb_it(ji,jj,jl)) * EXP( - ph_snw(ji,jj,jl) * z1_c1 ); 230 zalb_sm = rn_alb_smlt - ( rn_alb_smlt - zalb_it(ji,jj,jl)) * EXP( - ph_snw(ji,jj,jl) * z1_c2 ); 231 232 ! Snow albedo (MV I guess we could use rt0 instead of rt0_snow) 233 zswitch = MAX( 0._wp , SIGN( 1._wp , pt_ice(ji,jj,jl) - rt0_snow ) ) 234 zalb_st = zswitch * zalb_sm + ( 1._wp - zswitch ) * zalb_sf 235 236 ! Surface albedo 237 zswitch = MAX( 0._wp , SIGN( 1._wp , - ph_snw(ji,jj,jl) ) ) 238 pa_ice_os(ji,jj,jl) = ( 1._wp - zswitch ) * zalb_st + zswitch * zalb_it(ji,jj,jl) 239 240 END DO 241 END DO 242 END DO 243 ! 244 ! !--- Clear sky surface albedo 245 pa_ice_cs = pa_ice_os - ( - 0.1010 * pa_ice_os * pa_ice_os + 0.1933 * pa_ice_os - 0.0148 ); 246 ! 247 ! 248 ! !------------------------------------------ 249 CASE( 2 ) ! Fractional surface-based parameterization (2017) 250 ! !------------------------------------------ 251 ! MV: I propose this formulation that is more elegant, and more easy to expand towards 252 ! varying pond and snow fraction. 253 ! Formulation 1 has issues to handle ponds and snow together that can't easily be fixed. 254 ! This one handles it better, I believe. 255 ! 256 ! !== Snow, bare ice and ponded ice fractions ==! 257 ! 258 ! ! Specific fractions (zafrac) refer to relative area covered by snow within each ice category 259 ! 260 ! !--- Effective pond fraction (for now, we prevent melt ponds and snow at the same time) 261 zafrac_pnd = 0._wp 262 IF ( ld_pnd ) THEN 263 WHERE( ph_snw == 0._wp ) zafrac_pnd = pafrac_pnd ! Snow fully "shades" melt ponds 264 ENDIF 265 ! 266 ! !--- Specific snow fraction (for now, prescribed) 267 WHERE( ph_snw > 0._wp ) ; zafrac_snw = 1. 268 ELSEWHERE ; zafrac_snw = 0. 269 END WHERE 270 ! 271 ! !--- Specific ice fraction 272 zafrac_ice = 1. - zafrac_snw - zafrac_pnd 273 ! 274 ! !== Snow-covered, pond-covered, and bare ice albedos ==! 275 ! 276 ! !--- Bare ice albedo 277 z1_c1 = 1. / ( LOG(1.5) - LOG(0.05) ) 278 z1_c2 = 1. / 0.05 279 WHERE ( 1.5 < ph_ice ) ; zalb_ice = zalb 280 ELSEWHERE( 0.05 < ph_ice .AND. ph_ice <= 1.5 ) ; zalb_ice = zalb + ( 0.18 - zalb ) * z1_c1 * & 281 & ( LOG(1.5) - LOG(ph_ice) ) 282 ELSEWHERE ; zalb_ice = rn_alb_oce + ( 0.18 - rn_alb_oce ) * z1_c2 * ph_ice 283 END WHERE 284 ! 285 z1_c1 = 1. / 0.02 !--- Snow-covered ice albedo (freezing, melting cases) 286 z1_c2 = 1. / 0.03 287 ! 288 WHERE( pt_ice < rt0_snow ) ; zalb_snw = rn_alb_sdry - ( rn_alb_sdry - zalb_ice ) * EXP( - ph_snw * z1_c1 ) 289 ELSEWHERE ; zalb_snw = rn_alb_smlt - ( rn_alb_smlt - zalb_ice ) * EXP( - ph_snw * z1_c2 ) 290 END WHERE 291 ! 292 IF ( ld_pnd ) THEN !--- Depth-dependent ponded ice albedo 293 z1_href_pnd = 0.05 ! inverse of the characteristic length scale (Lecomte et al. 2015) 294 zalb_pnd = rn_alb_dpnd - ( rn_alb_dpnd - zalb_ice ) * EXP( - ph_pnd * z1_href_pnd ) 295 ELSE 296 zalb_pnd = rn_alb_dpnd 297 ENDIF 298 ! !--- Surface albedo is weighted mean of snow, ponds and bare ice contributions 299 pa_ice_os = zafrac_snw * zalb_snw + zafrac_pnd * zalb_pnd + zafrac_ice * zalb_ice 300 pa_ice_cs = pa_ice_os - ( - 0.1010 * pa_ice_os * pa_ice_os + 0.1933 * pa_ice_os - 0.0148 ) 301 302 END SELECT 171 END DO 172 ! 173 palb_cs(:,:,:) = palb_os(:,:,:) - ( - 0.1010 * palb_os(:,:,:) * palb_os(:,:,:) + 0.1933 * palb_os(:,:,:) - 0.0148 ) 303 174 ! 304 175 IF( nn_timing == 1 ) CALL timing_stop('icealb') … … 315 186 !! ** Method : Read the namelist namalb 316 187 !!---------------------------------------------------------------------- 317 INTEGER :: ios! Local integer output status for namelist read318 !! 319 NAMELIST/namalb/ nn_ice_alb,rn_alb_sdry, rn_alb_smlt, rn_alb_idry, rn_alb_imlt, rn_alb_dpnd188 INTEGER :: ios ! Local integer output status for namelist read 189 !! 190 NAMELIST/namalb/ rn_alb_sdry, rn_alb_smlt, rn_alb_idry, rn_alb_imlt, rn_alb_dpnd 320 191 !!---------------------------------------------------------------------- 321 192 ! … … 334 205 WRITE(numout,*) '~~~~~~~~~~~~' 335 206 WRITE(numout,*) ' Namelist namalb:' 336 WRITE(numout,*) ' choose the albedo parameterization nn_ice_alb = ', nn_ice_alb337 207 WRITE(numout,*) ' albedo of dry snow rn_alb_sdry = ', rn_alb_sdry 338 208 WRITE(numout,*) ' albedo of melting snow rn_alb_smlt = ', rn_alb_smlt
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