Leibniz Institute for Freshwater Ecology and Inland Fisheries, Ecohydrology, Müggelseedamm 310, 12587, Berlin, Germany.
GFZ German Research Centre for Geosciences, Remote Sensing, Telegrafenberg, 14473, Potsdam, Germany.
Sci Rep. 2019 Feb 4;9(1):1391. doi: 10.1038/s41598-018-37817-8.
Artificial light at night has affected most of the natural nocturnal landscapes worldwide and the subsequent light pollution has diverse effects on flora, fauna and human well-being. To evaluate the environmental impacts of light pollution, it is crucial to understand both the natural and artificial components of light at night under all weather conditions. The night sky brightness for clear skies is relatively well understood and a reference point for a lower limit is defined. However, no such reference point exists for cloudy skies. While some studies have examined the brightening of the night sky by clouds in urban areas, the published data on the (natural) darkening by clouds is very sparse. Knowledge of reference points for the illumination of natural nocturnal environments however, is essential for experimental design and ecological modeling to assess the impacts of light pollution. Here we use differential all-sky photometry with a commercial digital camera to investigate how clouds darken sky brightness at two rural sites. The spatially resolved data enables us to identify and study the nearly unpolluted parts of the sky and to set an upper limit on ground illumination for overcast nights at sites without light pollution.
夜间人工光照已经影响了全球大部分自然的夜间景观，随之而来的光污染对植物、动物和人类健康都有多种影响。为了评估光污染的环境影响，了解所有天气条件下夜间的自然和人工光源是至关重要的。晴朗天空的夜空亮度相对容易理解，并且定义了一个下限的参考点。然而，对于多云的天空，并没有这样的参考点。虽然一些研究已经研究了城市地区云层对夜空变亮的影响，但关于云层（自然）变暗的已发表数据非常稀少。然而，对于实验设计和生态建模来说，了解自然夜间环境照明的参考点对于评估光污染的影响是必不可少的。在这里，我们使用商业数字相机进行的全天空微分光度测量，研究了云层如何使两个农村地区的天空亮度变暗。空间分辨率数据使我们能够识别和研究天空中几乎未受污染的部分，并为没有光污染的地点设置了阴天地面照度的上限。
