! ! $Id$ ! SUBROUTINE ocean_albedo(knon,zrmu0,knindex,pwind,SFRWL,alb_dir_new,alb_dif_new) !! !!**** *ALBEDO_RS14* !! !! PURPOSE !! ------- !! computes the direct & diffuse albedo over open water !! !!** METHOD !! ------ !! !! EXTERNAL !! -------- !! !! IMPLICIT ARGUMENTS !! ------------------ !! !! REFERENCE !! --------- !! !! AUTHOR !! ------ !! R. Séférian * Meteo-France * !! !! MODIFICATIONS !! ------------- !! Original 03/2014 !! 05/2014 R. Séférian & B. Decharme :: Adaptation to spectral !! computation for diffuse and direct albedo !! 08/2014 S. Baek :: for wider wavelength range 200-4000nm and !! adaptation to LMDZ + whitecap effect by Koepke + chrolophyll !! map from climatology file !! 10/2016 O. Boucher :: some optimisation following R. !! Seferian's work in the CNRM Model !! !------------------------------------------------------------------------------- ! !* DECLARATIONS ! ------------ ! USE ocean_albedo_para USE dimphy USE phys_state_var_mod, ONLY : chl_con USE clesphys_mod_h ! ! IMPLICIT NONE ! !* 0.1 declarations of arguments ! ------------------------- ! ! INTEGER, INTENT(IN) :: knon INTEGER, DIMENSION(klon), INTENT(IN) :: knindex REAL, DIMENSION(klon), INTENT(IN) :: zrmu0 !--cos(SZA) on full vector REAL, DIMENSION(klon), INTENT(IN) :: pwind !--wind speed on compressed vector REAL, DIMENSION(6),INTENT(IN) :: SFRWL REAL, DIMENSION(klon,nsw), INTENT(OUT) :: alb_dir_new, alb_dif_new ! !* 0.2 declarations of local variables ! ------------------------- ! REAL, DIMENSION(klon) :: ZCHL ! surface chlorophyll REAL, DIMENSION(klon) :: ZCOSZEN ! Cosine of the zenith solar angle ! INTEGER :: JWL, INU ! indexes INTEGER :: JI REAL :: ZWL ! input parameter: wavelength and diffuse/direct fraction of light REAL:: ZCHLABS, ZAW, ZBW, ZREFM, ZYLMD, ZUE, ZUE2 ! scalar computation variables ! REAL, DIMENSION(klon) :: ZAP, ZXX2, ZR00, ZRR0, ZRRR ! computation variables REAL, DIMENSION(klon) :: ZR22, ZR11DF ! computation variables REAL, DIMENSION(klon) :: ZBBP, ZNU, ZHB ! computation variables REAL, DIMENSION(klon) :: ZR11, ZRW, ZRWDF, ZRDF ! 4 components of the OSA REAL, DIMENSION(klon) :: ZSIG, ZFWC, ZWORK1, ZWORK2, ZWORK3 ! !--initialisations------------- ! IF (knon==0) RETURN ! A verifier pourquoi on en a besoin... alb_dir_new(:,:) = 0. alb_dif_new(:,:) = 0. ! ! Initialisation of chlorophyll content ! ZCHL(:) = CHL_CON!0.05 ! averaged global values for surface chlorophyll IF (ok_chlorophyll) THEN ZCHL(1:knon)=CHL_CON(knindex(1:knon)) ELSE ZCHL(1:knon) = 0.05 ENDIF ! variables that do not depend on wavelengths ! loop over the grid points ! functions of chlorophyll content ZWORK1(1:knon)= EXP(LOG(ZCHL(1:knon))*0.65) ZWORK2(1:knon)= 0.416 * EXP(LOG(ZCHL(1:knon))*0.766) ZWORK3(1:knon)= LOG10(ZCHL(1:knon)) ! store the cosine of the solar zenith angle ZCOSZEN(1:knon) = zrmu0(knindex(1:knon)) ! Compute sigma derived from wind speed (Cox & Munk reflectance model) ZSIG(1:knon)=SQRT(0.003+0.00512*PWIND(1:knon)) ! original : correction for foam (Eq 16-17) ! has to be update once we have information from wave model (discussion with G. Madec) ZFWC(1:knon)=3.97e-4*PWIND(1:knon)**1.59 ! Salisbury 2014 eq(2) at 37GHz, value in fraction ! DO JWL=1,NNWL ! loop over the wavelengths ! !--------------------------------------------------------------------------------- ! 0- Compute baseline values !--------------------------------------------------------------------------------- ! Get refractive index for the correspoding wavelength ZWL=XAKWL(JWL) !!!--------- wavelength value ZREFM= XAKREFM(JWL) !!!--------- refraction index value !--------------------------------------------------------------------------------- ! 1- Compute direct surface albedo (ZR11) !--------------------------------------------------------------------------------- ! ZXX2(1:knon)=SQRT(1.0-(1.0-ZCOSZEN(1:knon)**2)/ZREFM**2) ZRR0(1:knon)=0.50*(((ZXX2(1:knon)-ZREFM*ZCOSZEN(1:knon))/(ZXX2(1:knon)+ZREFM*ZCOSZEN(1:knon)))**2 + & ((ZCOSZEN(1:knon)-ZREFM*ZXX2(1:knon))/(ZCOSZEN(1:knon)+ZREFM*ZXX2(1:knon)))**2) ZRRR(1:knon)=0.50*(((ZXX2(1:knon)-1.34*ZCOSZEN(1:knon))/(ZXX2(1:knon)+1.34*ZCOSZEN(1:knon)))**2 + & ((ZCOSZEN(1:knon)-1.34*ZXX2(1:knon))/(ZCOSZEN(1:knon)+1.34*ZXX2(1:knon)))**2) ZR11(1:knon)=ZRR0(1:knon)-(0.0152-1.7873*ZCOSZEN(1:knon)+6.8972*ZCOSZEN(1:knon)**2-8.5778*ZCOSZEN(1:knon)**3+ & 4.071*ZSIG(1:knon)-7.6446*ZCOSZEN(1:knon)*ZSIG(1:knon)) * & EXP(0.1643-7.8409*ZCOSZEN(1:knon)-3.5639*ZCOSZEN(1:knon)**2-2.3588*ZSIG(1:knon)+ & 10.0538*ZCOSZEN(1:knon)*ZSIG(1:knon))*ZRR0(1:knon)/ZRRR(1:knon) ! !--------------------------------------------------------------------------------- ! 2- Compute surface diffuse albedo (ZRDF) !--------------------------------------------------------------------------------- ! Diffuse albedo from Jin et al., 2006 + estimation from diffuse fraction of ! light (relying later on AOD). CNRM model has opted for Eq 5b ZRDF(1:knon)=-0.1482-0.012*ZSIG(1:knon)+0.1609*ZREFM-0.0244*ZSIG(1:knon)*ZREFM ! surface diffuse (Eq 5a) !!ZRDF(1:knon)=-0.1479+0.1502*ZREFM-0.0176*ZSIG(1:knon)*ZREFM ! surface diffuse (Eq 5b) !--------------------------------------------------------------------------------- ! *- Determine absorption and backscattering ! coefficients to determine reflectance below the surface (Ro) once for all ! ! *.1- Absorption by chlorophyll ZCHLABS= XAKACHL(JWL) ! *.2- Absorption by seawater ZAW= XAKAW3(JWL) ! *.3- Backscattering by seawater ZBW= XAKBW(JWL) ! *.4- Backscattering by chlorophyll ZYLMD = EXP(0.014*(440.0-ZWL)) ZAP(1:knon) = 0.06*ZCHLABS*ZWORK1(1:knon) +0.2*(XAW440+0.06*ZWORK1(1:knon))*ZYLMD !! WHERE ( ZCHL(1:knon) > 0.02 ) !! ZNU(:)=MIN(0.0,0.5*(ZWORK3(:)-0.3)) !! ZBBP(:)=(0.002+0.01*(0.5-0.25*ZWORK3(:))*(ZWL/550.)**ZNU(:))*ZWORK2(:) !! ELSEWHERE !! ZBBP(:)=0.019*(550./ZWL)*ZWORK2(:) !ZBBPf=0.0113 at chl<=0.02 !! ENDWHERE do JI = 1, knon IF (ZCHL(JI) > 0.02) THEN ZNU(JI)=MIN(0.0,0.5*(ZWORK3(JI)-0.3)) ZBBP(JI)=(0.002+0.01*(0.5-0.25*ZWORK3(JI))*(ZWL/550.)**ZNU(JI)) & *ZWORK2(JI) ELSE ZBBP(JI)=0.019*(550./ZWL)*ZWORK2(JI) !ZBBPf=0.0113 at chl<=0.02 ENDIF ENDDO ! Morel-Gentili(1991), Eq (12) ! ZHB=h/(h+2*ZBBPf*(1.-h)) ZHB(1:knon)=0.5*ZBW/(0.5*ZBW+ZBBP(1:knon)) !--------------------------------------------------------------------------------- ! 3- Compute direct water-leaving albedo (ZRW) !--------------------------------------------------------------------------------- ! Based on Morel & Gentilli 1991 parametrization ZR22(1:knon)=0.48168549-0.014894708*ZSIG(1:knon)-0.20703885*ZSIG(1:knon)**2 ! Use Morel 91 formula to compute the direct reflectance ! below the surface ZR00(1:knon)=(0.5*ZBW+ZBBP(1:knon))/(ZAW+ZAP(1:knon)) * & (0.6279-0.2227*ZHB(1:knon)-0.0513*ZHB(1:knon)**2 + & (-0.3119+0.2465*ZHB(1:knon))*ZCOSZEN(1:knon)) ZRW(1:knon)=ZR00(1:knon)*(1.-ZR22(1:knon))/(1.-ZR00(1:knon)*ZR22(1:knon)) !--------------------------------------------------------------------------------- ! 4- Compute diffuse water-leaving albedo (ZRWDF) !--------------------------------------------------------------------------------- ! as previous water-leaving computation but assumes a uniform incidence of ! shortwave at surface (ue) ZUE=0.676 ! equivalent u_unif for diffuse incidence ZUE2=SQRT(1.0-(1.0-ZUE**2)/ZREFM**2) ZRR0(1:knon)=0.50*(((ZUE2-ZREFM*ZUE)/(ZUE2+ZREFM*ZUE))**2 +((ZUE-ZREFM*ZUE2)/(ZUE+ZREFM*ZUE2))**2) ZRRR(1:knon)=0.50*(((ZUE2-1.34*ZUE)/(ZUE2+1.34*ZUE))**2 +((ZUE-1.34*ZUE2)/(ZUE+1.34*ZUE2))**2) ZR11DF(1:knon)=ZRR0(1:knon)-(0.0152-1.7873*ZUE+6.8972*ZUE**2-8.5778*ZUE**3+4.071*ZSIG(1:knon)-7.6446*ZUE*ZSIG(1:knon)) * & EXP(0.1643-7.8409*ZUE-3.5639*ZUE**2-2.3588*ZSIG(1:knon)+10.0538*ZUE*ZSIG(1:knon))*ZRR0(1:knon)/ZRRR(1:knon) ! Use Morel 91 formula to compute the diffuse ! reflectance below the surface ZR00(1:knon) = (0.5*ZBW+ZBBP(1:knon)) / (ZAW+ZAP(1:knon)) & * (0.6279-0.2227*ZHB(1:knon)-0.0513*ZHB(1:knon)**2 & + (-0.3119+0.2465*ZHB(1:knon))*ZUE) ZRWDF(1:knon)=ZR00(1:knon)*(1.-ZR22(1:knon))*(1.-ZR11DF(1:knon))/(1.-ZR00(1:knon)*ZR22(1:knon)) ! get waveband index inu for each nsw band SELECT CASE(nsw) CASE(2) IF (JWL.LE.49) THEN ! from 200 to 680 nm inu=1 ELSE ! from 690 to 4000 nm inu=2 ENDIF CASE(4) IF (JWL.LE.49) THEN ! from 200 to 680 nm inu=1 ELSE IF (JWL.LE.99) THEN ! from 690 to 1180 nm inu=2 ELSE IF (JWL.LE.218) THEN ! from 1190 to 2370 nm inu=3 ELSE ! from 2380 to 4000 nm inu=4 ENDIF CASE(6) IF (JWL.LE.5) THEN ! from 200 to 240 nm inu=1 ELSE IF (JWL.LE.24) THEN ! from 250 to 430 nm inu=2 ELSE IF (JWL.LE.49) THEN ! from 440 to 680 nm inu=3 ELSE IF (JWL.LE.99) THEN ! from 690 to 1180 nm inu=4 ELSE IF (JWL.LE.218) THEN ! from 1190 to 2370 nm inu=5 ELSE ! from 2380 to 4000 nm inu=6 ENDIF END SELECT ! partitionning direct and diffuse albedo ! excluding diffuse albedo ZRW on ZDIR_ALB !--direct alb_dir_new(1:knon,inu)=alb_dir_new(1:knon,inu) + & ( XFRWL(JWL) * ((1.-ZFWC(1:knon)) * (ZR11(1:knon)+ZRW(1:knon)) + ZFWC(1:knon)*XRWC(JWL)) )/SFRWL(inu) !--diffuse alb_dif_new(1:knon,inu)=alb_dif_new(1:knon,inu) + & ( XFRWL(JWL) * ((1.-ZFWC(1:knon)) * (ZRDF(1:knon)+ZRWDF(1:knon)) + ZFWC(1:knon)*XRWC(JWL)) )/SFRWL(inu) ENDDO ! ending loop over wavelengths END SUBROUTINE ocean_albedo