Variation of outdoor illumination as a function of solar elevation and light pollution.
The illumination of the environment undergoes both intensity and spectral changes during the 24 h cycle of a day. Daylight spectral power distributions are well described by low-dimensional models such as the CIE (Commission Internationale de l'Éclairage) daylight model, but the performance of this model in non-daylight regimes is not characterised. We measured downwelling spectral irradiance across multiple days in two locations in North America: One rural location (Cherry Springs State Park, PA) with minimal anthropogenic light sources, and one city location (Philadelphia, PA). We characterise the spectral, intensity and colour changes and extend the existing CIE model for daylight to capture twilight components and the spectrum of the night sky.
Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Manuel
M
Spitschan
Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Geoffrey K
GK
Aguirre
Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
David H
DH
Brainard
Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Alison M
AM
Sweeney
D002138:Calibration; D002947:Cities; D003116:Color; D008029:Lighting / Q000009:adverse effects; D008962:Models, Theoretical; D010414:Pennsylvania; D017440:Photoperiod; D000069079:Radiation Exposure; D012424:Rural Population; D019445:Solar Activity; D016082:Solar System; D013053:Spectrophotometry; D013472:Sunlight; D013997:Time Factors