Vaisala AWS330 - Manual (Page 285)

Appendix B ______________________________________________________ Calculation Formulas
VAISALA ______________________________________________________________________ 283
Calculation of Zenith Angle e
ω δ δ cos cos ) cos( sin ) ( arccos(sin ⋅ ⋅ + ⋅ = Lat Lat e
where
Lon =
Station longitude
Lat = Station latitude
π
δ
180
)) 2 sin( 000908 . 0
) 2 cos( 006758 . 0
sin 070257 . 0
cos 399912 . 0
006918 . 0 (
⋅ ⋅ +
⋅ −
⋅ +
⋅ −
=
A
A
A
A
15 ) 0 . 12 ( ⋅ − = TST
ω
365
1
360
−
⋅ =
DN
A
60
EQ
LMT TST + =
60
4
⋅ + = Lon GMT LMT
TS CT GMT − =
) 2 sin( 3619 . 9
) 2 cos( 3495 . 3
sin 3515 . 7
cos 4281 . 0
0172 . 0
A
A
A
A
EQ
⋅ −
⋅ −
⋅ −
⋅ +
=
where
δ = Declination (-24.0 ... 24.0 degrees)
ω = Hour Angle (-180.0 ... 180.0 degrees)
TST = True Solar Time (in decimals)
LMT = Local Mean Time (in decimals)
GMT = Greenwich Mean Time (in decimals)
CT
= Civil Time (in decimals)
TS = Time Shift