Mr. Asif:

Extra-terrestial solar radiation is solar radiation received above
atmosphere before the sunlight
goes through the atmosphere to reach the earth. it can be calculated by
following formula:

Ra=[(86400)(1360)/3.1416] * (dm/d)^2 *
[(Hs)*sin(a)*sin(b)+cos(a)*cos(b)*sin(Hs)]


                 Where:
                 Ra: extra-terrestrial solar radiation (MJm-2day-1)
                 Hs: solar angle at solar noon,
                 Hs = (90 - a + b) * 3.14159 / 180
                  a: is latitude of local station,
                  b: is solar declination, it varies from -23.5 to 23.5 for
each year. it can be                         calculated or simply given in
a table. contact me if you need the table.
                 dm: is the mean distance from the Sun to the Earth during
a year, and
                 d is the distance from the Sun to the Earth on daily basis.
  I also have table contains dm and d values for  recent years, contact me
if you need them.

Good luck!



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Zhisheng (Jason) Qing
PhD Candidate & Research Assistant
Agricultural and Biological Engineering Department
Clemson University
Clemson, SC 29631
Voice: 864 656 4079
Email: [log in to unmask]
Fax: 864 656 0338
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