A Simple Insolation Model
(Please read
this file
for an explanation of these calculations.)
INPUT VALUES:
Location, latitude (+N) and longitude (+E) decimal degrees
Date, year (YYYY) month (MM) day (DD)
Time, HH MM SS UTC
Barometric pressure, mb -- actual value ("station pressure") at site elevation
Total column water vapor, cm H
2
O
Aerosol transmission factor
Solar constant, W/m
2
SUN POSITION:
Solar zenith angle, deg
Azimuth angle, eastward from North
Relative air mass
Earth/sun radius, AU
Equation of time, minutes
(+ value means that solar noon occurs
before
clock noon at Greenwich Meridian.)
ATMOSPHERE VALUES:
T
r
T
g
T
w
T
a
INSOLATION DATA:
Insolation, W/m
2
Clock time for solar noon HH MM SS local
standard time
Add this many hours to get to UT
Zenith angle at solar noon
Azimuth angle, eastward from North
Relative air mass at solar noon
At solar noon, T
r
T
g
T
w
T
a
Maximum insolation for this day, W/m
2
Approximate day length, hours