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Kocifaj, M.; Petrzala, J. |
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Title |
Rapid approach to the quantitative determination of nocturnal ground irradiance in populated territories: a clear-sky case |
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Journal Article |
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Year |
2016 |
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Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
Mon. Not. R. Astron. Soc. |
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Volume  |
462 |
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3 |
Pages |
2739-2746 |
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Skyglow |
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A zero-order approach to the solving of the radiative transfer equation and a method for obtaining the horizontal diffuse irradiance at night-time are both developed and intended for wide use in numerical predictions of nocturnal ground irradiance in populated territories. Downward diffuse radiative fluxes are computed with a two-stream approximation, and the data products obtained are useful for scientists who require rapid estimations of illumination levels during the night. The rapid technique presented here is especially important when the entire set of calculations is to be repeated for different lighting technologies and/or radiant intensity distributions with the aim of identifying high-level illuminance/irradiance, the spectral composition of scattered light or other optical properties of diffuse light at the ground level. The model allows for the computation of diffuse horizontal irradiance due to light emissions from ground-based sources with arbitrary spectral compositions. The optical response of a night sky is investigated using the ratio of downward to upward irradiance, R⊥, λ(0). We show that R⊥, λ(0) generally peaks at short wavelengths, thus suggesting that, e.g., the blue light of an LED lamp would make the sky even more bluish. However, this effect can be largely suppressed or even removed with the spectral sensitivity function of the average human eye superimposed on to the lamp spectrum. Basically, blue light scattering dominates at short optical distances, while red light is transmitted for longer distances and illuminates distant places. Computations are performed for unshielded as well as fully shielded lights, while the spectral function R⊥, λ(0) is tabulated to make possible the modelling of various artificial lights, including those not presented here. |
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0035-8711 |
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LoNNe @ kyba @ |
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1517 |
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Kocifaj, M.; Kómar, L. |
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Title |
A role of aerosol particles in forming urban skyglow and skyglow from distant cities |
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Journal Article |
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Year |
2016 |
Publication |
Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
MNRAS |
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Volume |
458 |
Issue |
1 |
Pages |
438-448 |
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Skyglow; scattering; atmospheric effects; artificial light; numerical modeling; GIS-based modeling; light pollution |
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Aerosol particles may represent the largest uncertainty about skyglow change in many locations under clear sky conditions. This is because aerosols are ubiquitous in the atmosphere and influence the ground-reaching radiation in different ways depending on their concentrations, origins, shapes, sizes, and compositions. Large particles tend to scatter in Fraunhofer diffraction regime, while small particles can be treated in terms of Rayleigh formalism. However, the role of particle microphysics in forming the skyglow still remains poorly quantified. We have shown in this paper that the chemistry is somehow important for backscattering from large particles that otherwise work as efficient attenuators of light pollution if composed of absorbing materials. The contribution of large particles to the urban skyglow diminishes as they become more spherical in shape. The intensity of backscattering from non-absorbing particles is more-or-less linearly decreasing function of particle radius even if number size distribution is inversely proportional to the fourth power of particle radius. This is due to single particle backscattering that generally increases steeply as the particle radius approaches large values. Forward scattering depends on the particle shape but is independent of the material composition, thus allowing for a simplistic analytical model of skyglow from distant cities. The model we have developed is based on mean value theorem for integrals and incorporates the parametrizable Garstang's emission pattern, intensity decay along optical beam path, and near-forward scattering in an atmospheric environment. Such model can be used by modellers and experimentalists for rapid estimation of skyglow from distant light sources. |
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ICA, Slovak Academy of Sciences, Dúbravská Road 9, 845 03 Bratislava, Slovak Republic; kocifaj(at)savba.sk |
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Oxford Journals |
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English |
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IDA @ john @ |
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1361 |
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Author |
Smith, M. |
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Title |
Time to turn off the lights |
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2009 |
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Nature |
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Nature |
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457 |
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7225 |
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27 |
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Editorial; Animal Migration/radiation effects; Animals; Astronomy/trends; Conservation of Energy Resources/economics/trends; *Darkness; Environmental Pollution/*adverse effects/economics/*prevention & control; Equipment Design/trends; Humans; Lighting/*adverse effects/economics |
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Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile. msmith@ctio.noao.edu |
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0028-0836 |
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PMID:19122621 |
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LoNNe @ christopher.kyba @ |
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466 |
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Brainard, G.C.; Lewy, A.J.; Menaker, M.; Fredrickson, R.H.; Miller, L.S.; Weleber, R.G.; Cassone, V.; Hudson, D. |
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Title |
Effect of Light Wavelength on the Suppression of Nocturnal Plasma Melatonin in Normal Volunteersa |
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1985 |
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Annals of the New York Academy of Sciences |
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453 |
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1 |
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376-378 |
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Human Health |
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0077-8923 |
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LoNNe @ kagoburian @ |
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723 |
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Author |
Kocifaj, M.; Solano Lamphar, H.A.; Kundracik, F. |
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Title |
Retrieval of Garstang's emission function from all-sky camera images |
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Journal Article |
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2015 |
Publication |
Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
Mon. Not. R. Astron. Soc. |
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Volume |
453 |
Issue |
1 |
Pages |
819-827 |
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Keywords |
Skyglow; scattering; atmospheric effects; light pollution; methods: data analysis; methods: numerical methods: observational |
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Abstract |
The emission function from ground-based light sources predetermines the skyglow features to a large extent, while most mathematical models that are used to predict the night sky brightness require the information on this function. The radiant intensity distribution on a clear sky is experimentally determined as a function of zenith angle using the theoretical approach published only recently in MNRAS, 439, 3405–3413. We have made the experiments in two localities in Slovakia and Mexico by means of two digital single lens reflex professional cameras operating with different lenses that limit the system's field-of-view to either 180º or 167º. The purpose of using two cameras was to identify variances between two different apertures. Images are taken at different distances from an artificial light source (a city) with intention to determine the ratio of zenith radiance relative to horizontal irradiance. Subsequently, the information on the fraction of the light radiated directly into the upward hemisphere (F) is extracted. The results show that inexpensive devices can properly identify the upward emissions with adequate reliability as long as the clear sky radiance distribution is dominated by a largest ground-based light source. Highly unstable turbidity conditions can also make the parameter F difficult to find or even impossible to retrieve. The measurements at low elevation angles should be avoided due to a potentially parasitic effect of direct light emissions from luminaires surrounding the measuring site. |
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ICA, Slovak Academy of Sciences, Dúbravská Road 9, 845 03 Bratislava, Slovak Republic; kocifaj(at)savba.sk |
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Oxford Journals |
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English |
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English |
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0035-8711 |
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IDA @ john @ |
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1249 |
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