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Computation of solar radiation from sky cover

Computation of solar radiation from sky cover A procedure for estimating global solar radiation from sky cover is developed from the records of 47 stations in the United States with long periods of radiation observations during the 10‐year period, March 1961 through February 1971. It fits a general parabolic equation of the form Y = B + (1 − B)(1 − N)p to the observations, where Y is the observed global solar radiation divided by clear sky radiation and N is the sky cover. The variables B (the point at which the parabola crosses the y axis) and P (a variable parameter less than 1.0) are selected to minimize the sum of the errors (Y − Ycalc)2, where Ycalc is the calculated value of Y. The equation Y = B + (1 − B)(1 − N)0.61 is selected as most representative, and the B values in this equation that minimize the sum of the errors squared for the individual stations are shown in Figure 1. The average absolute error of the 5306 data points is 1.18 MJ m−2, or 7% of the average observed radiation. Because of the uncertainties of the observed global solar radiation and observed sky cover, the procedure should be used with caution, particularly for periods of less than 1 month. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Water Resources Research Wiley

Computation of solar radiation from sky cover

Thompson, Edwin S.
Water Resources Research , Volume 12 (5) – Oct 1, 1976
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References (4)

Publisher
Wiley
Copyright
Copyright © 1976 by the American Geophysical Union.
ISSN
0043-1397
eISSN
1944-7973
DOI
10.1029/WR012i005p00859
Publisher site
See Article on Publisher Site

Abstract

A procedure for estimating global solar radiation from sky cover is developed from the records of 47 stations in the United States with long periods of radiation observations during the 10‐year period, March 1961 through February 1971. It fits a general parabolic equation of the form Y = B + (1 − B)(1 − N)p to the observations, where Y is the observed global solar radiation divided by clear sky radiation and N is the sky cover. The variables B (the point at which the parabola crosses the y axis) and P (a variable parameter less than 1.0) are selected to minimize the sum of the errors (Y − Ycalc)2, where Ycalc is the calculated value of Y. The equation Y = B + (1 − B)(1 − N)0.61 is selected as most representative, and the B values in this equation that minimize the sum of the errors squared for the individual stations are shown in Figure 1. The average absolute error of the 5306 data points is 1.18 MJ m−2, or 7% of the average observed radiation. Because of the uncertainties of the observed global solar radiation and observed sky cover, the procedure should be used with caution, particularly for periods of less than 1 month.

Journal

Water Resources Research – Wiley

Published: Oct 1, 1976

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