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ZENSUN.f File Reference

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

Go to the source code of this file.

Functions/Subroutines

subroutine zensun (day, time, lat, lon, pi, sun_zenith, sun_azimuth)
 Makes sun zenith and sun azimuth angle.
 

Detailed Description

zensun() makes sun zenith and sun azimuth angle.

Author
Paul Ricchiazzi Earth Space Research Group,UCSB
Date
1992-10-23 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.

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 in file ZENSUN.f.

Function/Subroutine Documentation

◆ zensun()

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 
)

Makes sun zenith and sun azimuth angle.

Parameters
[in]dayinteger Julian day (positive scalar or vector), (spring equinox = 80), (summer solstice= 171), (fall equinox = 266), (winter solstice= 356).
[in]timereal Universal Time in hours (scalar or vector).
[in]latreal Geographic latitude of point on earth's surface (degrees).
[in]lonreal Geographic longitude of point on earth's surface (degrees).
[in]pireal The mathematical constant pi.
[out]sun_zenithreal Solar zenith angle.
[out]sun_azimuthreal Solar azimuth angle.

Definition at line 61 of file ZENSUN.f.

Referenced by calrad_wcloud(), initpost(), and initpost_mpas().