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C $Header: /u/gcmpack/MITgcm/pkg/exf/exf_zenithangle_table.F,v 1.1 2010/04/13 06:57:33 gforget Exp $ |
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C $Name: $ |
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#include "EXF_OPTIONS.h" |
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SUBROUTINE EXF_ZENITHANGLE_TABLE(myThid) |
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C ================================================================== |
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C SUBROUTINE exf_zenithangle_table |
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C ================================================================== |
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C |
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C o compute table of daily mean albedo that will be used in exf_zenithangle.F |
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C |
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C ================================================================== |
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C SUBROUTINE exf_zenithangle_table |
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C ================================================================== |
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IMPLICIT NONE |
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C == global variables == |
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#include "EEPARAMS.h" |
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#include "SIZE.h" |
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#include "PARAMS.h" |
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#include "DYNVARS.h" |
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#include "GRID.h" |
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#include "EXF_PARAM.h" |
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#include "EXF_FIELDS.h" |
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#include "EXF_CONSTANTS.h" |
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C == routine arguments == |
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INTEGER myThid |
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#ifdef ALLOW_DOWNWARD_RADIATION |
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#ifdef ALLOW_ZENITHANGLE |
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C == local variables == |
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INTEGER bi,bj |
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INTEGER i,j |
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_RL FSOL, dD0dDsq, SOLC, tmpINT1, tmpINT2 |
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_RL LLLAT, TYEAR, TDAY, ALPHA, CZEN, ALBSEA1 |
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_RL DECLI, ZS, ZC, SJ, CJ, TMPA, TMPB |
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integer iLat,iTyear,iTday |
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C == end of interface == |
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c solar constant |
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c -------------- |
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SOLC = 1368. _d 0 |
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DO bj = myByLo(myThid),myByHi(myThid) |
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DO bi = myBxLo(myThid),myBxHi(myThid) |
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DO iLat=1,181 |
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DO iTyear=1,366 |
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LLLAT=(iLat-91. _d 0) |
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TYEAR=(iTyear-1. _d 0)/365. _d 0 |
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c determine solar declination |
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c --------------------------- |
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c (formula from Hartmann textbook, after Spencer 1971) |
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ALPHA= 2. _d 0*PI*TYEAR |
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DECLI = 0.006918 _d 0 |
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& - 0.399912 _d 0 * cos ( 1. _d 0 * ALPHA ) |
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& + 0.070257 _d 0 * sin ( 1. _d 0 * ALPHA ) |
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& - 0.006758 _d 0 * cos ( 2. _d 0 * ALPHA ) |
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& + 0.000907 _d 0 * sin ( 2. _d 0 * ALPHA ) |
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& - 0.002697 _d 0 * cos ( 3. _d 0 * ALPHA ) |
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& + 0.001480 _d 0 * sin ( 3. _d 0 * ALPHA ) |
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ZC = COS(DECLI) |
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ZS = SIN(DECLI) |
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SJ = SIN(LLLAT * deg2rad) |
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CJ = COS(LLLAT * deg2rad) |
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TMPA = SJ*ZS |
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TMPB = CJ*ZC |
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c compute squared earth-sun distance ratio |
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c ---------------------------------------- |
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c (formula from Hartmann textbook, after Spencer 1971) |
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dD0dDsq = 1.000110 _d 0 |
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& + 0.034221 _d 0 * cos ( 1. _d 0 * ALPHA ) |
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& + 0.001280 _d 0 * sin ( 1. _d 0 * ALPHA ) |
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& + 0.000719 _d 0 * cos ( 2. _d 0 * ALPHA ) |
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& + 0.000077 _d 0 * sin ( 2. _d 0 * ALPHA ) |
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tmpINT1=0. _d 0 |
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tmpINT2=0. _d 0 |
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DO iTday=1,100 |
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TDAY=iTday/100. _d 0 |
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c determine DAILY VARYING cos of solar zenith angle CZEN |
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c ------------------------------------------------------ |
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CZEN = TMPA + TMPB * |
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& cos( 2. _d 0 *PI* TDAY + 0. _d 0 * deg2rad ) |
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if ( CZEN .LE.0 ) CZEN = 0. _d 0 |
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c compute incoming flux at the top of the atm.: |
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c --------------------------------------------- |
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FSOL = SOLC * dD0dDsq * MAX( 0. _d 0, CZEN ) |
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c determine direct ocean albedo |
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c ----------------------------- |
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c (formula from Briegleb, Minnis, et al 1986) |
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ALBSEA1 = ( ( 2.6 _d 0 / (CZEN**(1.7 _d 0) + 0.065 _d 0) ) |
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& + ( 15. _d 0 * (CZEN-0.1 _d 0) * (CZEN-0.5 _d 0) |
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& * (CZEN-1.0 _d 0) ) ) / 100.0 _d 0 |
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c accumulate averages |
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c ------------------- |
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tmpINT1=tmpINT1+FSOL*ALBSEA1/100. _d 0 |
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tmpINT2=tmpINT2+FSOL/100. _d 0 |
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ENDDO |
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c compute weighted average of albedo |
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c ---------------------------------- |
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if ( 0.5 _d 0 * tmpINT2 .GT. tmpINT1) then |
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zen_albedo_table(iTyear,iLat,bi,bj)=tmpINT1/tmpINT2 |
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else |
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zen_albedo_table(iTyear,iLat,bi,bj)=0.5 _d 0 |
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endif |
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ENDDO |
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ENDDO |
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ENDDO |
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ENDDO |
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c determine interpolation coefficient for each grid point |
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DO bj = myByLo(myThid),myByHi(myThid) |
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DO bi = myBxLo(myThid),myBxHi(myThid) |
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DO j = 1,sNy |
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DO i = 1,sNx |
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LLLAT=yC(i,j,bi,bj)+91. _d 0 |
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c ensure that it is in valid range |
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LLLAT=max(LLLAT, 1._d 0) |
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LLLAT=min(LLLAT, 181._d 0) |
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c store |
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zen_albedo_pointer(i,j,bi,bj)=LLLAT |
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ENDDO |
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ENDDO |
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ENDDO |
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ENDDO |
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#endif /* ALLOW_ZENITHANGLE */ |
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#endif /* ALLOW_DOWNWARD_RADIATION */ |
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RETURN |
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END |
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