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Kocifaj, M.; Solano Lamphar, H.A. |
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Title |
Quantitative analysis of night skyglow amplification under cloudy conditions |
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Journal Article |
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Year |
2014 |
Publication |
Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
Monthly Notices of the Royal Astronomical Society |
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Volume  |
443 |
Issue |
4 |
Pages |
3665-3674 |
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Keywords |
Skyglow; radiative transfer; scattering; atmospheric effects; light pollution; methods: numerical |
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Abstract |
The radiance produced by artificial light is a major source of nighttime over-illumination. It can, however, be treated experimentally using ground-based and satellite data. These two types of data complement each other and together have a high information content. For instance, the satellite data enable upward light emissions to be normalized, and this in turn allows skyglow levels at the ground to be modelled under cloudy or overcast conditions. Excessive night lighting imposes an unacceptable burden on nature, humans and professional astronomy. For this reason, there is a pressing need to determine the total amount of downwelling diffuse radiation. Undoubtedly, cloudy periods can cause a significant increase in skyglow as a result of amplification owing to diffuse reflection from clouds. While it is recognized that the amplification factor (AF) varies with cloud cover, the effects of different types of clouds, of atmospheric turbidity and of the geometrical relationships between the positions of an individual observer, the cloud layer, and the light source are in general poorly known. In this paper the AF is quantitatively analysed considering different aerosol optical depths (AODs), urban layout sizes and cloud types with specific albedos and altitudes. The computational results show that the AF peaks near the edges of a city rather than at its centre. In addition, the AF appears to be a decreasing function of AOD, which is particularly important when modelling the skyglow in regions with apparent temporal or seasonal variability of atmospheric turbidity. The findings in this paper will be useful to those designing engineering applications or modelling light pollution, as well as to astronomers and environmental scientists who aim to predict the amplification of skyglow caused by clouds. In addition, the semi-analytical formulae can be used to estimate the AF levels, especially in densely populated metropolitan regions for which detailed computations may be CPU-intensive. These new results are of theoretical and experimental significance as they will motivate experimentalists to collect data from various regions to build an overall picture of the AF, and will encourage modellers to test the consistency with theoretical predictions. |
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0035-8711 |
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LoNNe @ christopher.kyba @ |
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538 |
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Kyba, C.C.M.; Ruhtz, T.; Fischer, J.; Hölker, F. |
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Title |
Red is the new black: how the colour of urban skyglow varies with cloud cover |
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Journal Article |
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Year |
2012 |
Publication |
Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
Monthly Notices of the Royal Astronomical Society |
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Volume |
425 |
Issue |
1 |
Pages |
701-708 |
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Keywords: skyglow; radiative transfer; atmospheric effects; instrumentation: detectors; light pollution |
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The development of street lamps based on solid-state lighting technology is likely to introduce a major change in the colour of urban skyglow (one form of light pollution). We demonstrate the need for long-term monitoring of this trend by reviewing the influences it is likely to have on disparate fields. We describe a prototype detector which is able to monitor these changes, and could be produced at a cost low enough to allow extremely widespread use. Using the detector, we observed the differences in skyglow radiance in red, green and blue channels. We find that clouds increase the radiance of red light by a factor of 17.6, which is much larger than that for blue (7.1). We also find that the gradual decrease in sky radiance observed on clear nights in Berlin appears to be most pronounced at longer wavelengths. |
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0035-8711 |
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IDA @ john @ |
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272 |
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Crumey, A. |
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Human Contrast Threshold and Astronomical Visibility. |
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Journal Article |
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2014 |
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Monthly Notices of the Royal Astronomical Society |
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MNRAS |
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422 |
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3 |
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2600-2619 |
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Keywords |
Vision; visibility; skyglow; sky brightness; modeling |
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The standard visibility model in light-pollution studies is the formula of Hecht, as used e.g. by Schaefer. However, it is applicable only to point sources and is shown to be of limited accuracy. A new visibility model is presented for uniform achromatic targets of any size against background luminances ranging from zero to full daylight, produced by a systematic procedure applicable to any appropriate data set (e.g. Blackwell's), and based on a simple but previously unrecognized empirical relation between contrast threshold and adaptation luminance. The scotopic luminance correction for variable spectral radiance (colour index) is calculated. For point sources, the model is more accurate than Hecht's formula and is verified using telescopic data collected at Mount Wilson in 1947, enabling the sky brightness at that time to be determined. The result is darker than the calculation by Garstang, implying that light pollution grew more rapidly in subsequent decades than has been supposed. The model is applied to the nebular observations of William Herschel, enabling his visual performance to be quantified. Proposals are made regarding sky quality indicators for public use. |
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Department of Humanities, Northumbria University, Newcastle upon Tyne NE1 8ST, UK; andrew.crumey(at)northumbria.ac.uk |
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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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LoNNe @ christopher.kyba @ |
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536 |
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Kocifaj, M.; Aubé, M.; Kohút, I. |
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Title |
The effect of spatial and spectral heterogeneity of ground-based light sources on night-sky radiances: Light pollution for heterogeneous sources |
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Journal Article |
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2010 |
Publication |
Monthly Notices of the Royal Astronomical Society |
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Volume |
409 |
Issue |
3 |
Pages |
1203-1212 |
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Keywords |
light pollution; scattering; atmospheric effects; methods: numerical |
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Nowadays, light pollution is a permanent problem at many observatories around the world. Elimination of excessive lighting during the night is not only about reduction of the total luminous power of ground-based light sources, but also involves experimenting with the spectral features of single lamps. Astronomical photometry is typically made at specific wavelengths, and thus the analysis of the spectral effects of light pollution is highly important. Nevertheless, studies on the spectral behaviour of night light are quite rare. Instead, broad-band or integral quantities (such as sky luminance) are preferentially measured and modelled. The knowledge of night-light spectra is necessary for the proper interpretation of narrow-band photometry data. In this paper, the night-sky radiances in the nominal spectral lines of the B (445 nm) and V (551 nm) filters are determined numerically under clear-sky conditions. Simultaneously, the corresponding sky-luminance patterns are computed and compared against the spectral radiances. It is shown that spectra, patterns and distances of the most important light sources (towns) surrounding an observatory are essential for determining the light pollution levels. In addition, the optical characteristics of the local atmosphere can change the angular behaviour of the sky radiance or luminance. All these effects are evaluated for two Slovakian observatories: Stará Lesná and Vartovka. |
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0035-8711 |
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IDA @ john @ |
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259 |
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Author |
Quinn, G.E.; Shin, C.H.; Maguire, M.G.; Stone, R.A. |
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Title |
Myopia and ambient lighting at night |
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Journal Article |
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Year |
1999 |
Publication |
Nature |
Abbreviated Journal |
Nature |
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Volume |
399 |
Issue |
6732 |
Pages |
113-114 |
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Keywords |
Human Health |
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Myopia, or short-sightedness, occurs when the image of distant objects, focused by the cornea and lens, falls in front of the retina. It commonly arises from excessive postnatal eye growth, particularly in the vitreous cavity. Its prevalence is increasing and now reaches 70-90% in some Asian populations1,2. As well as requiring optical correction, myopia is a leading risk factor for acquired blindness in adults because it predisposes individuals to retinal detachment, retinal degeneration and glaucoma. It typically develops in the early school years but can manifest into early adulthood2. Its aetiology is poorly understood but may involve genetic and environmental factors1,2, such as viewing close objects, although how this stimulates eye growth is not known3. We have looked at the effects of light exposure on vision, and find a strong association between myopia and night-time ambient light exposure during sleep in children before they reach two years of age. |
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0028-0836 |
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PMID:10335839 |
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GFZ @ kyba @ |
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2550 |
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