The Natural Redistribution of Sunlight and Skylight Due to the Atmospheric Turbidity of Cloudless Skies

ABSTRACT

The transmittance and absorption of sunlight as well as the scattering properties of the atmosphere can be characterized by the luminous turbidity factor, which also determines the redistribution of sunlight and skylight at the ground level. The International Organization for Standardization (ISO)/CIE cloudless sky types defining the quasi-homogeneous luminance sky patterns enable calculation of either the relative distribution of luminance on the sky vault or the redistribution of absolute sunlight and skylight illuminance levels on the ground. Applying appropriate formulae, this article shows the consequences of turbidity changes on such redistribution in the case of rising solar altitudes; for example, when the ISO/CIE clear sky type 12 occurs during a summer day.

KEYWORDS:

• Cloudless ISO/CIE sky types
• global illuminance
• luminous atmospheric turbidity
• sunlight and skylight illuminance

Funding

This work was supported by Research Agency of The Ministry of Education, Science, Research and Sport of the Slovak Republic research grants of the Slovak Research and Development Agency APVV-0118-12 and VEGA 02/0042/17.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.

Additional information

Funding

This work was supported by Slovak research grants APVV-0118-12 and VEGA 02/0042/17.