The impact of clouds on the brightness of the night sky
Level 4 - case-series / case-control
Observational environmental measurement study (by design analogy, not clinical CEBM)
OpenAlex W3011582680 · doi:10.1016/j.jqsrt.2020.106962
What was done
The authors analyzed the impact of cloud cover, cloud genera, and cloud base altitude on night sky brightness across locations with varying degrees of baseline light pollution. Continuous all-night sky brightness measurements were combined with meteorological data and cloud genera assessments, including a method to infer certain cloud genera directly from sky brightness patterns when observational cloud data were unavailable.
What was found
The abstract reports qualitative relationships without specific numerical values. A linear correlation was observed between cloudiness and night sky brightness, allowing categorization into three distinct light-pollution area types. Among nine identified cloud genera, Altocumulus, Cirrocumulus, and Cumulonimbus were primarily responsible for this correlation. Night sky brightness did not depend on cloud albedo. Under overcast skies, brightness was inversely related to cloud altitude, with lowest-altitude cloud genera contributing the most scattered light. Additionally, at freezing temperatures, an aerosol layer formed below Nimbostratus or Stratus clouds that thickened as temperature dropped, adding further artificial light scattering.
Why it matters
The study characterizes how specific meteorological conditions and cloud types amplify artificial light pollution at ground level. This provides an observational basis for modeling nighttime sky brightness and urban light scattering under different atmospheric conditions.
Limits
The abstract does not disclose sample sizes, the number or geographic distribution of measurement stations, observation duration, or statistical metrics (such as correlation coefficients or confidence intervals). Findings may be specific to the regional climates and lighting conditions measured.
Cited by
- supports Skyglow occurs when artificial light from Earth reflects off clouds and atmospheric particles back down to the surface, increasing ambient brightness.