Yes, clouds do make light pollution worse, especially for observers within light-emitting cities.
How Clouds Amplify Light Pollution
Clouds worsen light pollution primarily due to the way they interact with artificial light emitted from the ground. The key mechanisms include:
- Reflection: Clouds reflect artificial light back towards the ground, increasing the overall brightness of the night sky.
- Transmission: Light can pass through clouds, scattering as it does so, which spreads the light over a wider area.
- Absorption: Clouds absorb some of the light. While this might seem like it would reduce light pollution, the absorbed light is often re-emitted in different directions, contributing to the general skyglow.
- Scattering: Similar to how sunlight is scattered by the atmosphere (creating blue skies), artificial light is scattered by water droplets and ice crystals within clouds, further diffusing the light.
The Cloud Cover Effect: Amplifying Light
The provided reference clearly states that cloud cover amplifies light pollution for observers located within light-emitting cities. This happens because, in addition to the normal scattering and absorption of light below the cloud layer, the cloud layer itself reflects, transmits, and absorbs artificial light from the ground. It essentially acts as a giant reflector, trapping and redistributing light within the urban environment.
Summary of the Cloud and Light Pollution Relationship
| Cloud Interaction | Effect on Light Pollution |
|---|---|
| Reflection | Increases skyglow |
| Transmission | Spreads light over a wider area |
| Absorption | Contributes to diffuse skyglow |
| Scattering | Further diffuses artificial light |
