Red is the new black: how the colour of urban skyglow varies with cloud cover

Kyba, Christopher C. M.; Ruhtz, Thomas; Fischer, Jürgen; Hölker, Franz

doi:10.1111/j.1365-2966.2012.21559.x

Cited by 97 publications

(95 citation statements)

References 40 publications

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“…These results are consistent with those obtained by Kyba et al for moderate degrees of cloud coverage (Table 2 of Ref. [18]), in spite of the fact that the observational data are not directly comparable: the data reported in [18] correspond to the average brightness measured within a Gaussian field of view of 20º (FWHM) centered at the zenith, recorded using R, G and B conventional color filters. The multiplicative role of the clouds in the Zernike space can also be assessed in Figure 8, that shows the cloud multiplication factor (CMF) for each radial order of the Zernike spectrum.…”

Section: Cloud Multiplication Factor In the Zernike Spacesupporting

confidence: 90%

Zernike power spectra of clear and cloudy light-polluted urban night skies

et al. 2015

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Received Month X, XXXX; revised Month X, XXXX; accepted Month X, XXXX; posted Month X, XXXX (Doc. ID XXXXX); published Month X, XXXX The Zernike power spectra of the all-sky night brightness distributions of clear and cloudy nights are computed using a modal projection approach. The results obtained in the B, V and R Johnson-Cousins' photometric bands during a one-year campaign of observations at a light-polluted urban site show that these spectra can be described by simple power laws with exponents close to −3 for clear nights and −2 for cloudy ones. The second-moment matrices of the Zernike coefficients show relevant correlations between modes. The multiplicative role of the cloud cover, that contributes to a significant increase of the brightness of the urban night sky in comparison with the values obtained in clear nights, is described in the Zernike space. 1.IntroductionThe constant increase of the sky glow produced by the anthropogenic emissions of light is one unwanted side-effect of the continuous spread of public and private lighting systems. A considerable amount of research is being devoted to the measurement and characterization of this phenomenon, in order to get reliable data for modeling accurately its propagation [1−6], to understand better its consequences in diverse fields [7−14], and to devise practicable strategies to keep it within acceptable limits [15−16].The multiplicative role of the cloud cover is also a matter of concern. Clouds greatly enhance the night sky brightness by reflecting (scattering) the upward radiation of the city lights. Urban overcast skies may reach radiances an order of magnitude higher than the corresponding clear skies, and four times bigger than rural clear moonlit nights [17−19]. Overall, the present levels of light pollution in many places across the world amount to a substantial change in the natural conditions of the nighttime environment.A widespread technique for monitoring the night sky brightness is based on the use of all-sky cameras with hemispheric field-of-view [20−23] that record with good spatial resolution the sky radiance in standard astronomical photometric bands like the B, V, and R Johnson-Cousins' set [24]. In a previous work [25] we have shown that the all-sky night brightness maps obtained in clear and moonless nights can be efficiently described in terms of Zernike polynomials [26−27]. Using this approach the information content of each map is condensed into an equivalent small-sized vector whose elements (the Zernike coefficients) have a definite physical meaning.Besides achieving a significant level of essentially lossless data compression, the study of the hemispherical night sky brightness may benefit that way from the conceptual and computational tools associated with modal analysis.As an example of application we described in that work the modal composition of clear and moonless urban night skies in the range of low to mid Zernike frequencies (radial orders 10 ≤ n ). While an expansion up to this order is generally enough for a succes...

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Section: Cloud Multiplication Factor In the Zernike Spacesupporting

confidence: 90%

Zernike power spectra of clear and cloudy light-polluted urban night skies

et al. 2015

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“…ii The factor which is essentially determining the night sky brightness at lightpolluted urban sites is the degree of cloudiness (see also Kyba et al [5]), since clouds strongly enhance the backscattering of artificial light in the atmosphere.…”

Section: Discussionmentioning

confidence: 99%

“…The best one can do without spectroscopy is attaching a set of SQMs parallel to each other, each equipped with a standard photometric filter (LRGB or UBVR). Such a configuration makes it possible to study the NSB development and to record possible changes in the color of the night sky at the same time (see Kyba et al [5]). …”

Section: Spectral Response Function Of the Sqm And Comparison To The mentioning

confidence: 99%

Night sky photometry and spectroscopy performed at the Vienna University Observatory

Puschnig

Posch

Uttenthaler

2014

Journal of Quantitative Spectroscopy and Radiative Transfer

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We present night sky brightness measurements performed at the Vienna University Observatory and at the Leopold-Figl-Observatorium für Astrophysik, which is located about 35km to the southwest of Vienna. The measurements have been performed with Sky Quality Meters made by Unihedron. They cover a time span of roughly one year and have been carried out every night, yielding a night sky brightness value every 7 seconds and thus delivering a large amount of data. In this paper, the level of light pollution in Vienna, which ranges from 15 to 19.25 mag SQM arcsec −2 is presented for the very first time in a systematic way. We discuss the influence of different environmental conditions on the night sky brightness and implications for human vision. We show that the circalunar rhythm of night sky brightness is extinguished at our observatory due to light pollution.Additionally, we present spectra of the night sky in Vienna, taken with a 0.8m telescope. The goal of these spectroscopic measurements was to identify the main types of light sources and the spectral lines which cause the light pollution in Vienna. It turned out that fluorescent lamps are responsible for the strongest lines of the night sky above Vienna (e.g. lines at 546 nm and at 611 nm).

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“…Recently, more advanced SQM measurements have been carried out in Berlin, Germany (Kyba et al 2012). The aim of these measurements was to research the changes in the spectrum of the artificial sky glow, for different wavelengths, and their dependence on cloud cover.…”

Section: H I S To Ry O F M E a S U R E M E N T Smentioning

confidence: 99%

Particulate matter as an amplifier for astronomical light pollution

Ściężor¹,

Kubala²

2014

Monthly Notices of the Royal Astronomical Society

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In this paper, we state that the main factor that influences seasonal changes in the brightness of the cloudless, moonless, light-polluted night sky is primarily particulate matter, emitted mainly from low-emission sources, especially in winter. This effect is particularly noticeable in Cracow and its surroundings, one of the places in Europe that is most polluted by particulate matter. Measurements taken over a period of one year have allowed us to show a linear relationship between the concentration of particulate matter and the brightness of the clear, cloudless night sky. We have also found similar correlations in other, industrialized areas of Poland, as well as at the Mount Suhora Astronomical Observatory. We believe that the factor described here should be taken into account when planning the construction of new astronomical observatories, especially those located near large urban areas.

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Red is the new black: how the colour of urban skyglow varies with cloud cover

Cited by 97 publications

References 40 publications

Zernike power spectra of clear and cloudy light-polluted urban night skies

Zernike power spectra of clear and cloudy light-polluted urban night skies

Night sky photometry and spectroscopy performed at the Vienna University Observatory

Particulate matter as an amplifier for astronomical light pollution

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