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Author |
Kocifaj, M.; Kundracik, F. |
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Title |
Multi-wavelength radiometry of aerosols designed for more accurate night sky brightness predictions |
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Journal Article |
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Year |
2020 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
Journal of Quantitative Spectroscopy and Radiative Transfer |
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Volume |
250 |
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Pages |
106998 |
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Keywords |
Skyglow; Remote Sensing |
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Abstract |
Scattering by aerosols and gases cause a certain fraction of artificial light emitted upwards is redirected to the ground. Of all atmospheric constituents just the aerosols are most important modulators of night-sky brightness under cloudless conditions. Unlike most of the previous we highlight a crucial role of solar radiometry for determining the atmospheric optical depth before night-time observation is to be made. Aerosol optical depth at visible wavelengths extracted from the data measured provides then the information on size distribution or mean refractive index of aerosol particles that in turn are both necessary to make night sky brightness prediction more accurate. Therefore, combining daytime and night-time radiometry we can achieve accuracy much higher than ever before. This is due to significantly reduced uncertainty in aerosol properties.
The aerosol data are retrieved from a new portable multi-wavelength optical analyzer that operates Ocean Optics spectrometer. The equipment provides the radiance data from 350 nm to 1000 nm with spectral resolution of 1 nm. Due to high sun radiance levels we use a system of mirrors each reducing the signal to about 4%, while keeping the integration time short. The minimum integration time of 3 ms allows for detection of direct sunlight. The system developed is sensitive to small changes in the aerosol system, while showing a good detection limit even under low turbidity conditions. The system performance is demonstrated in field experiment conducted shortly after front passage when most of aerosol particles is effectively removed by rain. |
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0022-4073 |
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GFZ @ kyba @ |
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2906 |
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Author |
Lamphar, H. |
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Title |
Spatio-temporal association of light pollution and urban sprawl using remote sensing imagery and GIS: A simple method based in Otsu's algorithm |
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Journal Article |
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Year |
2020 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
Journal of Quantitative Spectroscopy and Radiative Transfer |
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251 |
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107060 |
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Remote Sensing |
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Automatic thresholding methods are used to detect spatio-temporal changes in the land subject to different natural and anthropogenic processes. Image segmentation plays an important role in this analysis, where urban sprawl detection take place with daylight images. However, recently some investigators have used nocturnal images in remote sensing imagery research. Such georeferenced data represent a good tool for analysis of the light pollution and urban sprawl. There are various physical processes involved in the radiative transfer of the light projected from the cities. Though, with a correct method based on background subtraction, any satellite remotely sensed nocturnal image can be useful in detecting urban sprawl. We base this work on thresholding processes of georeferenced nocturnal satellite images. We used a method combining digital classification techniques, geographic information systems and statistical analyzes. The proposed method is helpful because of a simple implementation and time saving. The pixel intensity of nocturnal images can offer a tool to calculate aspects related to electricity consumption and the efficiency of public lighting. We hope the results motivates other authors to study relationships with other social, natural and economic issues. |
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0022-4073 |
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GFZ @ kyba @ |
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2990 |
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Barentine, J.C.; Kundracik, F.; Kocifaj, M.; Sanders, J.C.; Esquerdo, G.A.; Dalton, A.M.; Foott, B.; Grauer, A.; Tucker, S.; Kyba, C.C.M. |
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Recovering the city street lighting fraction from skyglow measurements in a large-scale municipal dimming experiment |
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Journal Article |
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Year |
2020 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
Journal of Quantitative Spectroscopy and Radiative Transfer |
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253 |
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107120 |
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Skyglow; Remote Sensing |
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Anthropogenic skyglow dominates views of the natural night sky in most urban settings, and the associated emission of artificial light at night (ALAN) into the environment of cities involves a number of known and suspected negative externalities. One approach to lowering consumption of ALAN in cities is dimming or extinguishing publicly owned outdoor lighting during overnight hours; however, there are few reports in the literature about the efficacy of these programs. Here we report the results of one of the largest municipal lighting dimming experiments to date, involving ~ 20,000 roadway luminaires owned and operated by the City of Tucson, Arizona, U.S. We analyzed both single-channel and spatially resolved ground-based measurements of broadband night sky radiance obtained during the tests, determining that the zenith sky brightness during the tests decreased by ()% near the city center and ()% at an adjacent suburban location on nights when the output of the street lighting system was dimmed from 90% of its full power draw to 30% after local midnight. Modeling these changes with a radiative transfer code yields results suggesting that street lights account for about (14 ± 1)% of light emissions resulting in skyglow seen over the city. A separate derivation from first principles implies that street lighting contributes only % of light seen at the zenith over Tucson. We discuss this inconsistency and suggest routes for future work. |
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3223 N 1st Ave, Tucson, AZ 85719; john(at)darksky.org |
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Elsevier |
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English |
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Enlish |
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0022-4073 |
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GFZ @ kyba @ |
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2989 |
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Author |
Kocifaj, M. |
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Title |
Ground albedo impacts on higher-order scattering spectral radiances of night sky |
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Journal Article |
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Year |
2019 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
Journal of Quantitative Spectroscopy and Radiative Transfer |
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239 |
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106670 |
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skyglow |
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The contribution from ground reflected light to the night sky radiance is of increased interest because of constant modernization of street lighting systems that now efficiently eliminate light emissions above the horizontal plane, so the appreciable fraction of artificial light directed upwards is from ground reflection. Diffuse light of a night sky shows a positive correlation with ground albedo (α), but it seems there is no linear trend between α and the night sky brightness (NSB), at least not for all sky elements, and, the mechanism of this relationship becomes even more complicated due to multiple scattering effects. The extent to which the ground reflectance influences the higher-order scattering radiance of night sky, and, the factors that initiate the crossover from single- to multiple-scattering dominance of the sky glow has been virtually unexplored until now.
We demonstrate here that albedo-induced effects in NSB exhibit an angular dependence, with amplitudes enhanced towards shorter wavelengths. For low values of ground reflectance and at short distances from a light source, the second-scattering radiance is found to be only a few percent of the first-order scattering radiance. However, the ratio of a higher- to the first-order scattering radiance gradually increases near horizon, specifically at the side opposite to the azimuthal position of the light source. Also the NSB in blue band has decreasing gradation tendency when increasing the altitude above sea level. The findings in this paper are significant in a proper incorporation of higher-order scattering in modeling the NSB under elevated reflectance conditions, and may be critical for saving computational time. |
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0022-4073 |
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GFZ @ kyba @ |
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2679 |
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Author |
Bará, S.; Rigueiro, I.; Lima, R.C. |
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Title |
Monitoring transition: Expected night sky brightness trends in different photometric bands |
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Journal Article |
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Year |
2019 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
Journal of Quantitative Spectroscopy and Radiative Transfer |
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Volume |
239 |
Issue |
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Pages |
106644 |
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Keywords |
Skyglow; Remote Sensing; Instrumentation |
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Several light pollution indicators are commonly used to monitor the effects of the transition from outdoor lighting systems based on traditional gas-discharge lamps to solid-state light sources. In this work we analyze a subset of these indicators, including the artificial zenithal night sky brightness in the visual photopic and scotopic bands, the brightness in the specific photometric band of the widely used Sky Quality Meter (SQM), and the top-of-atmosphere radiance detected by the VIIRS-DNB radiometer onboard the satellite Suomi-NPP. Using a single-scattering approximation in a layered atmosphere we quantitatively show that, depending on the transition scenarios, these indicators may show different, even opposite behaviors. This is mainly due to the combined effects of the changes in the sources' spectra and angular radiation patterns, the wavelength-dependent atmospheric propagation processes and the differences in the detector spectral sensitivity bands. It is suggested that the possible presence of this differential behavior should be taken into account when evaluating light pollution indicator datasets for assessing the outcomes of public policy decisions regarding the upgrading of outdoor lighting systems. |
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0022-4073 |
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Call Number |
GFZ @ kyba @ |
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2810 |
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