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Georgiadis, M., Mavraki, N., Koutsikopoulos, C., & Tzanatos, E. (2014). Spatio-temporal dynamics and management implications of the nightly appearance of Boops boops (Acanthopterygii, Perciformes) juvenile shoals in the anthropogenically modified Mediterranean littoral zone. Hydrobiologia, 734(1), 81–96.
Abstract: A remarkable phenomenon of dense Boops boops shoals appearing almost adjacent to the shoreline during nighttime is known to the locals of island communities of the Aegean Sea (eastern Mediterranean). In this work, we investigated this appearance testing the hypotheses that (a) it may occur only in anthropogenically modified locations (as suggested by previous observations), (b) the migration pattern to the littoral is not arbitrary but synchronized to the sunset/sunrise, (c) fish abundance is affected by location, season and/or natural (moon) light fluctuations. Quantitative sampling included visual observations from the coast at five stations in Syros (Cyclades, Greece) from July 2009 to September 2010. Both hypotheses concerning occurrence only in anthropogenically modified locations and timing with sunset/sunrise were confirmed. Fish abundance was modelled using generalized additive models, demonstrating a seasonal pattern and revealing significant differences among sampling stations, but no moon-phase effects. The phenomenon investigated here has implications for fisheries management, as the shoal proximity to the shore renders them prone to illegal harvesting (seasonally at high abundances), aggravating the problem of illegal, unreported and unregulated fishing. Further considerations on the integrated management of the coastal zone arise, especially concerning the effects of habitat structural modification and light pollution.
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Tollefson, J. (2014). Energy: Islands of Light. Nature, 507(7491), 154–156.
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Sciezor, T., & Kubala, M. (2014). Particulate matter as an amplifier for astronomical light pollution. Monthly Notices of the Royal Astronomical Society, 444(3), 2487–2493.
Abstract: 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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Kocifaj, M., & Solano Lamphar, H. A. (2014). Quantitative analysis of night skyglow amplification under cloudy conditions. Monthly Notices of the Royal Astronomical Society, 443(4), 3665–3674.
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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Kocifaj, M., & Solano Lamphar, H. A. (2014). Skyglow: a retrieval of the approximate radiant intensity function of ground-based light sources. Monthly Notices of the Royal Astronomical Society, 439(4), 3405–3413.
Abstract: The angular distribution of the light emitted from a city is an important source of information about public lighting systems and it also plays a key role in modelling the skyglow. Usually, the upwardly directed radiation is characterized through a parametrized emission function – a semi-empirical approach as a reasonable approximation that allows for fast computations. However, theoretical or experimental retrievals of emission characteristics are extremely difficult to obtain because of both the complexity of radiative transfer methods and/or the lack of highly specialized measuring devices.
Our research has been conducted with the specific objective to identify an efficient theoretical technique for retrieval of the emission pattern of ground-based light sources in order to determine the optimum values of the scaling parameters of the Garstang function. In particular, the input data involve the zenith luminance or radiance with horizontal illuminance or irradiance. Theoretical ratios of zenith luminance LV(0) to horizontal illuminance DV are calculated for a set of distances d that separate a hypothetical observer from the light source (a city or town). This approach is advantageous because inexpensive traditional equipment can be used to obtain the mean values of the Garstang parameters. Furthermore, it can also be applied to other parametrizable emission functions and to any measuring site, even one with a masked horizon.
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