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Spectral distribution of solar radiation. I: Direct radiation
Author(s) -
McCartney H. A.,
Unsworth M. H.
Publication year - 1978
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49710444112
Subject(s) - zenith , irradiance , solar irradiance , solar zenith angle , solar constant , wavelength , radiation , spectral power distribution , attenuation , air mass (solar energy) , optics , atmospheric sciences , environmental science , turbidity , range (aeronautics) , attenuation coefficient , aerosol , physics , meteorology , materials science , geology , oceanography , boundary layer , composite material , thermodynamics
Measurements of the spectral distribution of direct solar radiation, made in both wide and narrow wavebands, are reported. The measurements suggest that the wavelength dependence of aerosol attenuation in central England, in summer, can generally be described by a power law with wavelength exponent of about 1.7. Attenuation of visible radiation is reported in terms of an integral turbidity coefficient, τ v , and is shown to depend to some extent on air mass origin, air masses from the continent being more turbid than maritime air masses. The mean value of τ v a is 0.31 with a range of 0.05 to 0.6. The ratio of visible to total direct irradiance is found to be a linear function of τ v , the constants of linearity being functions of zenith angle. From these relationships a semi‐empirical model is developed enabling spectral irradiance, visible irradiance and total solar irradiance to be estimated from arbitrary values of turbidity and zenith angle.