ZENSUN.f File Reference

zensun() makes sun zenith and sun azimuth angle. More...

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Functions/Subroutines
subroutine	zensun (day, time, lat, lon, pi, sun_zenith, sun_azimuth)
	This subroutine computes solar position information as a function of geographic coordinates, date and time. More...

Detailed Description

zensun() makes sun zenith and sun azimuth angle.

Author

Paul Ricchiazzi Earth Space Research Group,UCSB

Date

1992-10-23

Definition in file ZENSUN.f.

Function/Subroutine Documentation

subroutine zensun	(	integer(i_kind), intent(in)	day,
		real(r_kind), intent(in)	time,
		real(r_kind), intent(in)	lat,
		real(r_kind), intent(in)	lon,
		real(r_kind), intent(in)	pi,
		real(r_kind), intent(out)	sun_zenith,
		real(r_kind), intent(out)	sun_azimuth
	)

This subroutine computes solar position information as a function of geographic coordinates, date and time.

Note

Procedure:

1. Calculate the subsolar point latitude and longitude, based on DAY and TIME. Since each year is 365.25 days long the exact value of the declination angle changes from year to year. For precise values consult THE AMERICAN EPHEMERIS AND NAUTICAL ALMANAC published yearly by the U.S. govt. printing office. The subsolar coordinates used in this code were provided by a program written by Jeff Dozier.
2. Given the subsolar latitude and longitude, spherical geometry is used to find the solar zenith, azimuth and flux multiplier.

eqt = equation of time (minutes) ! solar longitude correction = -15*eqt dec = declination angle (degrees) = solar latitude

LOWTRAN v7 data (25 points) The LOWTRAN solar position data is characterized by only 25 points. This should predict the subsolar angles within one degree. For increased accuracy add more data points.

nday=[ 1., 9., 21., 32., 44., 60., 91., 121., 141., 152.,$ 160., 172., 182., 190., 202., 213., 244., 274., 305., 309.,$ 325., 335., 343., 355., 366.]

eqt=[ -3.23, -6.83,-11.17,-13.57,-14.33,-12.63, -4.2, 2.83, 3.57, 2.45,$ 1.10, -1.42, -3.52, -4.93, -6.25, -6.28,-0.25, 10.02, 16.35, 16.38,$ 14.3, 11.27, 8.02, 2.32, -3.23]

dec=[-23.07,-22.22,-20.08,-17.32,-13.62, -7.88, 4.23, 14.83, 20.03, 21.95,$ 22.87, 23.45, 23.17, 22.47, 20.63, 18.23, 8.58, -2.88,-14.18,-15.45,$ -19.75,-21.68,-22.75,-23.43,-23.07]

Analemma information from Jeff Dozier

This data is characterized by 74 points.

Parameters

[in]	day	integer Julian day (positive scalar or vector), (spring equinox = 80), (summer solstice= 171), (fall equinox = 266), (winter solstice= 356).
[in]	time	real Universal Time in hours (scalar or vector).
[in]	lat	real Geographic latitude of point on earth's surface (degrees).
[in]	lon	real Geographic longitude of point on earth's surface (degrees).
[in]	pi	real The mathematical constant pi.
[out]	sun_zenith	real Solar zenith angle.
[out]	sun_azimuth	real Solar azimuth angle.

Program history log:

Date	Programmer	Comments
2005-10-21	kazumori	Reformatted for GSI

Author

Paul Ricchiazzi Earth Space Research Group,UCSB

Date

1992-10-23

Definition at line 62 of file ZENSUN.f.

Referenced by initpost().