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module swde_m |
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IMPLICIT NONE |
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contains |
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SUBROUTINE swde(pgg, pref, prmuz, pto1, pw, 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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! ------------------------------------------------------------------ |
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! PURPOSE. |
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! -------- |
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! COMPUTES THE REFLECTIVITY AND TRANSMISSIVITY OF A CLOUDY |
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! LAYER USING THE DELTA-EDDINGTON'S APPROXIMATION. |
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! METHOD. |
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! ------- |
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! STANDARD DELTA-EDDINGTON LAYER CALCULATIONS. |
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! REFERENCE. |
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! ---------- |
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! SEE RADIATION'S PART OF THE MODEL'S DOCUMENTATION AND |
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! ECMWF RESEARCH DEPARTMENT DOCUMENTATION OF THE IFS |
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! AUTHOR. |
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! ------- |
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! JEAN-JACQUES MORCRETTE *ECMWF* |
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! MODIFICATIONS. |
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! -------------- |
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! ORIGINAL : 88-12-15 |
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! ------------------------------------------------------------------ |
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! * ARGUMENTS: |
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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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! * LOCAL VARIABLES: |
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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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! ------------------------------------------------------------------ |
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! * 1. DELTA-EDDINGTON CALCULATIONS |
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DO jl = 1, kdlon |
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! * 1.1 SET UP THE DELTA-MODIFIED PARAMETERS |
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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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! MAF 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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! MAF 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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! * 1.2 WITHOUT REFLECTION FROM THE UNDERLYING LAYER |
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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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! * 1.3 WITH REFLECTION FROM THE UNDERLYING LAYER |
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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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END DO |
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RETURN |
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END SUBROUTINE swde |
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end module swde_m |
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