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SUBROUTINE SWDE (PGG,PREF,PRMUZ,PTO1,PW, |
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S PRE1,PRE2,PTR1,PTR2) |
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use dimens_m |
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use dimphy |
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use raddim |
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IMPLICIT none |
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C |
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C ------------------------------------------------------------------ |
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C PURPOSE. |
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C -------- |
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C COMPUTES THE REFLECTIVITY AND TRANSMISSIVITY OF A CLOUDY |
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C LAYER USING THE DELTA-EDDINGTON'S APPROXIMATION. |
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C |
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C METHOD. |
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C ------- |
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C |
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C STANDARD DELTA-EDDINGTON LAYER CALCULATIONS. |
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C |
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C REFERENCE. |
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C ---------- |
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C |
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C SEE RADIATION'S PART OF THE MODEL'S DOCUMENTATION AND |
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C ECMWF RESEARCH DEPARTMENT DOCUMENTATION OF THE IFS |
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C |
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C AUTHOR. |
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C ------- |
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C JEAN-JACQUES MORCRETTE *ECMWF* |
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C |
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C MODIFICATIONS. |
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C -------------- |
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C ORIGINAL : 88-12-15 |
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C ------------------------------------------------------------------ |
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C* ARGUMENTS: |
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C |
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DOUBLE PRECISION PGG(KDLON) ! ASSYMETRY FACTOR |
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DOUBLE PRECISION PREF(KDLON) ! REFLECTIVITY OF THE UNDERLYING LAYER |
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DOUBLE PRECISION PRMUZ(KDLON) ! COSINE OF SOLAR ZENITH ANGLE |
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DOUBLE PRECISION PTO1(KDLON) ! OPTICAL THICKNESS |
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DOUBLE PRECISION PW(KDLON) ! SINGLE SCATTERING ALBEDO |
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DOUBLE PRECISION PRE1(KDLON) ! LAYER REFLECTIVITY (NO UNDERLYING-LAYER REFLECTION) |
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DOUBLE PRECISION PRE2(KDLON) ! LAYER REFLECTIVITY |
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DOUBLE PRECISION PTR1(KDLON) ! LAYER TRANSMISSIVITY (NO UNDERLYING-LAYER REFLECTION) |
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DOUBLE PRECISION PTR2(KDLON) ! LAYER TRANSMISSIVITY |
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C |
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C* LOCAL VARIABLES: |
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C |
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INTEGER jl |
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DOUBLE PRECISION ZFF, ZGP, ZTOP, ZWCP, ZDT, ZX1, ZWM |
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DOUBLE PRECISION ZRM2, ZRK, ZX2, ZRP, ZALPHA, ZBETA, ZARG |
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DOUBLE PRECISION ZEXMU0, ZARG2, ZEXKP, ZEXKM, ZXP2P, ZXM2P, ZAP2B |
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DOUBLE PRECISION ZAM2B |
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DOUBLE PRECISION ZA11, ZA12, ZA13, ZA21, ZA22, ZA23 |
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DOUBLE PRECISION ZDENA, ZC1A, ZC2A, ZRI0A, ZRI1A |
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DOUBLE PRECISION ZRI0B, ZRI1B |
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DOUBLE PRECISION ZB21, ZB22, ZB23, ZDENB, ZC1B, ZC2B |
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DOUBLE PRECISION ZRI0C, ZRI1C, ZRI0D, ZRI1D |
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C ------------------------------------------------------------------ |
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C |
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C* 1. DELTA-EDDINGTON CALCULATIONS |
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C |
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100 CONTINUE |
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C |
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DO 131 JL = 1, KDLON |
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C |
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C* 1.1 SET UP THE DELTA-MODIFIED PARAMETERS |
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C |
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110 CONTINUE |
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C |
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ZFF = PGG(JL)*PGG(JL) |
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ZGP = PGG(JL)/(1.+PGG(JL)) |
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ZTOP = (1.- PW(JL) * ZFF) * PTO1(JL) |
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ZWCP = (1-ZFF)* PW(JL) /(1.- PW(JL) * ZFF) |
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ZDT = 2./3. |
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ZX1 = 1.-ZWCP*ZGP |
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ZWM = 1.-ZWCP |
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ZRM2 = PRMUZ(JL) * PRMUZ(JL) |
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ZRK = SQRT(3.*ZWM*ZX1) |
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ZX2 = 4.*(1.-ZRK*ZRK*ZRM2) |
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ZRP=ZRK/ZX1 |
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ZALPHA = 3.*ZWCP*ZRM2*(1.+ZGP*ZWM)/ZX2 |
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ZBETA = 3.*ZWCP* PRMUZ(JL) *(1.+3.*ZGP*ZRM2*ZWM)/ZX2 |
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CMAF ZARG=MIN(ZTOP/PRMUZ(JL),200.) |
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ZARG=MIN(ZTOP/PRMUZ(JL),2.0d+2) |
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ZEXMU0=EXP(-ZARG) |
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CMAF ZARG2=MIN(ZRK*ZTOP,200.) |
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ZARG2=MIN(ZRK*ZTOP,2.0d+2) |
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ZEXKP=EXP(ZARG2) |
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ZEXKM = 1./ZEXKP |
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ZXP2P = 1.+ZDT*ZRP |
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ZXM2P = 1.-ZDT*ZRP |
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ZAP2B = ZALPHA+ZDT*ZBETA |
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ZAM2B = ZALPHA-ZDT*ZBETA |
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C |
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C* 1.2 WITHOUT REFLECTION FROM THE UNDERLYING LAYER |
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C |
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120 CONTINUE |
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C |
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ZA11 = ZXP2P |
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ZA12 = ZXM2P |
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ZA13 = ZAP2B |
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ZA22 = ZXP2P*ZEXKP |
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ZA21 = ZXM2P*ZEXKM |
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ZA23 = ZAM2B*ZEXMU0 |
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ZDENA = ZA11 * ZA22 - ZA21 * ZA12 |
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ZC1A = (ZA22*ZA13-ZA12*ZA23)/ZDENA |
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ZC2A = (ZA11*ZA23-ZA21*ZA13)/ZDENA |
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ZRI0A = ZC1A+ZC2A-ZALPHA |
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ZRI1A = ZRP*(ZC1A-ZC2A)-ZBETA |
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PRE1(JL) = (ZRI0A-ZDT*ZRI1A)/ PRMUZ(JL) |
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ZRI0B = ZC1A*ZEXKM+ZC2A*ZEXKP-ZALPHA*ZEXMU0 |
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ZRI1B = ZRP*(ZC1A*ZEXKM-ZC2A*ZEXKP)-ZBETA*ZEXMU0 |
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PTR1(JL) = ZEXMU0+(ZRI0B+ZDT*ZRI1B)/ PRMUZ(JL) |
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C |
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C* 1.3 WITH REFLECTION FROM THE UNDERLYING LAYER |
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C |
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130 CONTINUE |
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C |
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ZB21 = ZA21- PREF(JL) *ZXP2P*ZEXKM |
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ZB22 = ZA22- PREF(JL) *ZXM2P*ZEXKP |
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ZB23 = ZA23- PREF(JL) *ZEXMU0*(ZAP2B - PRMUZ(JL) ) |
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ZDENB = ZA11 * ZB22 - ZB21 * ZA12 |
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ZC1B = (ZB22*ZA13-ZA12*ZB23)/ZDENB |
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ZC2B = (ZA11*ZB23-ZB21*ZA13)/ZDENB |
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ZRI0C = ZC1B+ZC2B-ZALPHA |
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ZRI1C = ZRP*(ZC1B-ZC2B)-ZBETA |
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PRE2(JL) = (ZRI0C-ZDT*ZRI1C) / PRMUZ(JL) |
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ZRI0D = ZC1B*ZEXKM + ZC2B*ZEXKP - ZALPHA*ZEXMU0 |
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ZRI1D = ZRP * (ZC1B*ZEXKM - ZC2B*ZEXKP) - ZBETA*ZEXMU0 |
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PTR2(JL) = ZEXMU0 + (ZRI0D + ZDT*ZRI1D) / PRMUZ(JL) |
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C |
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131 CONTINUE |
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RETURN |
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END |