Standard distributions of clear sky radiance

✍ Scribed by Michael D. Steven; Dr M. H. Unsworth

• Book ID: 104574687
• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 507 KB
• Volume: 103
• Category: Article
• ISSN: 0035-9009
• DOI: 10.1002/qj.49710343706

✦ Synopsis

Abstract

Diffuse radiation from cloudless skies varies with solar height and atmospheric turbidity but its angular distribution remains generally characteristic of single scattering. It was found that when sky radiance measurements, N, were normalized with respect to horizontal diffuse irradiance, S~d~, the angular distributions of N/S~d~ were remarkably independent of atmospheric turbidity. This enabled standard distributions of normalized sky radiance, based on a long series of measurements on clear skies, to be drawn up for different solar zenith angles. Due to the difference between radiometric and photometric units these distributions are not comparable with previously published luminance distributions. Departures due to variation in atmospheric turbidity, of the radiance distributions from the proposed standards, were analysed and found to be small for the range of turbidities (τ~α~ from 0·1 to 0·5) normally encountered in Britain.