城区的光污染使夜空变亮20倍 | R. Soc. open sci 论文推荐

来源 Phys.org

撰文 Bob Yirka

翻译 郑邦晓

审校 金庄维

加利西亚夜空亮度监测网络的探测器分布，它们分别位于当地的14个气象站

一位西班牙物理学家发现，人工照明系统导致城市上空的亮度高出自然区域20倍以上。来自圣地亚哥·德·孔波斯特拉大学（Universidade de Santiago deCompostela）的萨尔多瓦·巴拉博士撰文详述了位于伊比利亚半岛西北部的光探网络如何测量天空亮度，明确揭示了夜幕下的某些区域到底有多亮。文章发表于《皇家学会开放科学》（可开放获取）。

光污染问题虽然由来已久，但科学家仍不清楚它对动植物以及我们人类的影响究竟有多大。为了对家乡的光污染程度了解更多，巴拉和他的助手在伊比利亚半岛的14个自动气象站上安装了光探测器。这些探测器分布在城市、郊区以及乡村，它们每分钟读数一次，并将数据自动上传至一个公开网站。巴拉利用这些数据定义了两个指标，显著亮度和月光调节因子，分别用于衡量晴朗夜空（无云无月）的亮度和月光的影响。

通过数据分析，巴拉发现：城市晴朗夜空的亮度通常是自然环境下的14~23倍，城郊地区则是7~8倍，城乡接合部是1.6~2.5倍，而乡村及山区只有0.8~1.6倍。他注意到云朵的出现会使夜空的亮度增强25倍。

一年中夜空亮度的变化。从左到右从上到下分别为城市、城郊、城乡接合部和乡村。刻度值越低代表亮度越高。周期性月光信号在下方两张图中比较明显，而在上方两张图中基本丢失。

巴拉同样发现，在乡村和城乡接合部月光带来的亮度变化清晰可见，而在城区内却难以分辨。他还指出，很多人工灯光侵入了本不该被照亮的区域，不仅浪费，也可能对远居世外的动植物造成不良影响。

加利西亚夜空亮度监测网络的介绍及测量数据：

http://webspersoais.usc.es/persoais/salva.bara/GalicianNSBnetwork.html

原文链接：http://phys.org/news/2016-10-detector-pollution-brighter-areas.html

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论文信息

【题目】Anthropogenic disruption of thenight sky darkness in urban and rural areas

【作者】Salvador Bará (Applied PhysicsDepartment, Universidade de Santiago de Compostela)

【期刊】R. Soc. open sci. 3: 160541

【日期】Published 19 October 2016

【DOI】http://dx.doi.org/10.1098/rsos.160541

【摘要】

The growing emissions of artificial light tothe atmosphere are producing, among other effects, a significant increase ofthe night sky brightness (NSB) above its expected natural values. A permanentsensor network has been deployed in Galicia (northwest of Iberian peninsula) tomonitor the anthropogenic disruption of the night sky darkness in a countrywidearea. The network is composed of 14 detectors integrated in automated weatherstations of MeteoGalicia, the Galician public meteorological agency. ZenithalNSB readings are taken every minute and the results are openly available inreal time for researchers, interested stakeholders and the public at largethrough a dedicated website. The measurements allow one to assess the extent ofthe loss of the natural night in urban, periurban, transition and dark ruralsites, as well as its daily and monthly time courses. Two metrics areintroduced here to characterize the disruption of the night darkness across theyear: the significant magnitude (m_1/3) and the moonlight modulation factor (γ). The significantmagnitude shows that in clear and moonless nights the zenithal night sky in theanalysed urban settings is typically 14–23 times brighter than expected from anominal natural dark sky. This factor lies in the range 7–8 in periurban sites,1.6–2.5 in transition regions and 0.8–1.6 in rural and mountain dark skyplaces. The presence of clouds in urban areas strongly enhances the amount ofscattered light, easily reaching amplification factors in excess of 25, incomparison with the light scattered in the same places under clear skyconditions. The periodic NSB modulation due to the Moon, still clearly visiblein transition and rural places, is barely notable at periurban locations and ispractically lost at urban sites.

【链接】http://rsos.royalsocietypublishing.org/content/royopensci/3/10/160541.full.pdf

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