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SUBROUTINE SOLAR_LOC(YR,T1,MEAN_LONG,DECLINATION)
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IMPLICIT NONE
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c
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c $Revision: 1.1 $
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c
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c
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c This subroutine converts the year and time of the year (from
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c cnv_mdhms_sec) to the mean solar longitude of the sun and the
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c solar declination.
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C
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C Imported by Bill Rideout on April 21, 2010
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C Modified by nag_apt to convert all reals to double, int16 to ints
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C
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C $Id: solar_loc.f 3304 2011-01-17 15:25:59Z brideout $
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c
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c*****************************************************************
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c Log: solar_loc.f,v
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c Revision 1.2 94/10/17 12:37:51 12:37:51 baker (Kile Baker S1G)
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c corrected some of the constants
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c
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c Revision 1.1 94/10/14 11:29:42 11:29:42 baker (Kile Baker S1G)
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c Initial revision
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c
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c
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c*****************************************************************
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INTEGER*4 YR,YR_STEP,DELTA_YR,I,IYR
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INTEGER*4 T1
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INTEGER*4 INDEX
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DOUBLE PRECISION MEAN_LONG,DECLINATION
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DOUBLE PRECISION D,LAMBDA,G,EPS,L
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DOUBLE PRECISION L0(10)
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DOUBLE PRECISION DL
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DOUBLE PRECISION G0(10)
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DOUBLE PRECISION DG
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DOUBLE PRECISION EPS0(10)
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DOUBLE PRECISION DE
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SAVE
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D = 0
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DATA L0/279.642D0,279.403D0,279.165D0,278.926D0,
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+ 279.673D0,
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+ 279.434D0,279.196D0,278.957D0,279.704D0,279.465D0/
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DL = 0.985647D0
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DATA G0/356.892984D0,356.637087D0,356.381191D0,
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+ 356.125295D0,
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+ 356.854999D0,356.599102D0,356.343206D0,356.087308D0,
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+ 356.817011D0,356.561113D0/
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DG = 0.98560028D0
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DATA EPS0/23.440722D0,23.440592D0,23.440462D0,
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+ 23.440332D0,
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+ 23.440202D0,23.440072D0,23.439942D0,23.439811D0,
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+ 23.439679D0,23.439548D0/
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DE = -0.00000036D0
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IF (YR.LT.1900) THEN
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INDEX = YR - 88
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ELSE
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INDEX = YR - 1988
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END IF
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c print *,'input values = ',yr,t1
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c print *, 'index = ',index
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IF (INDEX.LE.0) THEN
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DELTA_YR = INDEX - 1
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ELSE IF (INDEX.GT.10) THEN
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DELTA_YR = INDEX - 10
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ELSE
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DELTA_YR = 0
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END IF
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IF (INDEX.LE.0) INDEX = 1
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IF (INDEX.GT.10) INDEX = 10
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YR_STEP = SIGN(1,DELTA_YR)
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DELTA_YR = ABS(DELTA_YR)
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c print *,'delta_yr =',delta_yr
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DO I = 1,DELTA_YR
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IF (YR_STEP.GT.0) THEN
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IYR = 98 + I - 1
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ELSE
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IYR = 89 - I
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END IF
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IF (MOD(IYR,4).EQ.0) THEN
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D = D + 366*YR_STEP
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ELSE
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D = D + 365*YR_STEP
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END IF
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END DO
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c print *,'before using t1, d=',d
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D = D + T1/86400.D0
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c print *,'after using t1, d=',d
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L = L0(INDEX) + DL*D
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G = G0(INDEX) + DG*D
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DO WHILE (L.LT.0)
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L = L + 360.D0
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END DO
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DO WHILE (G.LT.0)
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G = G + 360.D0
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END DO
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C*PT*WARNING* Constant already double-precision
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L = MOD(L,360.0d0)
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C*PT*WARNING* Constant already double-precision
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G = MOD(G,360.0d0)
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LAMBDA = L + 1.915D0*DSIN(G) + 0.020D0*DSIN(2*G)
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EPS = EPS0(INDEX) + DE*D
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DECLINATION = DASIN(DSIN(EPS)*DSIN(LAMBDA))
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MEAN_LONG = L
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RETURN
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END
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