A User's Manual for DELSOL3 - prod.sandia.gov - Sandia National ...

1II.B-I. Position 01 the Sun-The sun position vector 8 is specified by (e,, pa)
as illustrated in Figure 11-2. If refraction effects in the atmosphere are ignored, 8,
and ,Ob can be calculated by (References 15 and 16):
where
cos& = sinXsin6 + cosXcos6cosr
sin& = sinrcos6/sin8,
X = latitude (> 0 in northern hemisphere),
(1II.B - 1)
(I11.B - 2)
r = hour angle measured from noon (> 0 in afternoon; 15' per hour),
6 = declination.
6 is determined by:
where
$(radians) = $0 + 0.007133sin$o
and
sin6 = sin(23.442274') sin$
+ 0.032680~0~~0 - 0.000318sin2$0
+ 0.000145cos2$0 (Reference 17)
%(DAY + 284.)
"= 365.24
(111.B - 3)
(I1I.B - 4)
(I1I.B - 5)
The effect of atmospheric refraction is to make the sun's apparent zenith an-
gle 8; (i.e., the zenith angle observed through the atmosphere) less than the true
zenith angle 8,. The correction is given by a numerical fit (Reference 18):
A8,(radians) = 8, - St
where
68
(II1.B - 6)