| 1 | SUBROUTINE vdif_cd( ngrid,pz0,pg,pz,pu,pv,pts,ph,pcdv,pcdh) |
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| 2 | USE planet, ONLY : karman |
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| 3 | IMPLICIT NONE |
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| 4 | c======================================================================= |
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| 5 | c |
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| 6 | c Subject: computation of the surface drag coefficient using the |
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| 7 | c ------- approch developed by Loui for ECMWF. |
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| 8 | c |
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| 9 | c Author: Frederic Hourdin 15 /10 /93 |
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| 10 | c ------- |
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| 11 | c |
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| 12 | c Arguments: |
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| 13 | c ---------- |
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| 14 | c |
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| 15 | c inputs: |
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| 16 | c ------ |
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| 17 | c ngrid size of the horizontal grid |
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| 18 | c pg gravity (m s -2) |
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| 19 | c pz(ngrid) height of the first atmospheric layer |
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| 20 | c pu(ngrid) u component of the wind in that layer |
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| 21 | c pv(ngrid) v component of the wind in that layer |
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| 22 | c pts(ngrid) surfacte temperature |
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| 23 | c ph(ngrid) potential temperature T*(p/ps)^kappa |
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| 24 | c |
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| 25 | c outputs: |
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| 26 | c -------- |
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| 27 | c pcdv(ngrid) Cd for the wind |
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| 28 | c pcdh(ngrid) Cd for potential temperature |
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| 29 | c |
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| 30 | c======================================================================= |
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| 31 | c |
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| 32 | c----------------------------------------------------------------------- |
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| 33 | c Declarations: |
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| 34 | c ------------- |
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| 35 | |
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| 36 | c Arguments: |
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| 37 | c ---------- |
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| 38 | |
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| 39 | INTEGER ngrid,nlay |
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| 40 | REAL pz0(ngrid) |
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| 41 | REAL pg,pz(ngrid) |
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| 42 | REAL pu(ngrid),pv(ngrid) |
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| 43 | REAL pts(ngrid),ph(ngrid) |
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| 44 | REAL pcdv(ngrid),pcdh(ngrid) |
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| 45 | |
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| 46 | c Local: |
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| 47 | c ------ |
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| 48 | |
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| 49 | INTEGER ig |
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| 50 | |
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| 51 | REAL zu2,z1,zri,zcd0,zz |
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| 52 | |
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| 53 | REAL b,c,d,c2b,c3bc,c3b,z0,umin2 |
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| 54 | LOGICAL firstcal |
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| 55 | DATA b,c,d,umin2/5.,5.,5.,1.e-12/ |
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| 56 | DATA firstcal/.true./ |
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| 57 | SAVE b,c,d,c2b,c3bc,c3b,firstcal,umin2 |
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| 58 | |
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| 59 | c----------------------------------------------------------------------- |
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| 60 | c couche de surface: |
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| 61 | c ------------------ |
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| 62 | |
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| 63 | c DO ig=1,ngrid |
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| 64 | c zu2=pu(ig)*pu(ig)+pv(ig)*pv(ig)+umin2 |
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| 65 | c pcdv(ig)=pz0(ig)*(1.+sqrt(zu2)) |
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| 66 | c pcdh(ig)=pcdv(ig) |
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| 67 | c ENDDO |
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| 68 | c RETURN |
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| 69 | |
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| 70 | IF (firstcal) THEN |
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| 71 | c2b=2.*b |
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| 72 | c3bc=3.*b*c |
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| 73 | c3b=3.*b |
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| 74 | firstcal=.false. |
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| 75 | ENDIF |
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| 76 | |
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| 77 | c!!!! WARNING, verifier la formule originale de Louis! |
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| 78 | DO ig=1,ngrid |
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| 79 | zu2=pu(ig)*pu(ig)+pv(ig)*pv(ig)+umin2 |
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| 80 | zri=pg*pz(ig)*(ph(ig)-pts(ig))/(ph(ig)*zu2) |
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| 81 | z1=1.+pz(ig)/pz0(ig) |
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| 82 | zcd0=karman/log(z1) |
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| 83 | zcd0=zcd0*zcd0*sqrt(zu2) |
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| 84 | IF(zri.LT.0.) THEN |
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| 85 | z1=b*zri/(1.+c3bc*zcd0*sqrt(-z1*zri)) |
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| 86 | pcdv(ig)=zcd0*(1.-2.*z1) |
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| 87 | pcdh(ig)=zcd0*(1.-3.*z1) |
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| 88 | ELSE |
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| 89 | zz=sqrt(1.+d*zri) |
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| 90 | pcdv(ig)=zcd0/(1.+c2b*zri/zz) |
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| 91 | pcdh(ig)=zcd0/(1.+c3b*zri*zz) |
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| 92 | ENDIF |
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| 93 | ENDDO |
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| 94 | |
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| 95 | c----------------------------------------------------------------------- |
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| 96 | |
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| 97 | RETURN |
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| 98 | END |
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