It is important to understand that the night sky is not typically brighter when it rains. In fact, the presence of rain and clouds usually makes the night sky darker, due to the absorption and scattering of light. The provided reference clarifies that as the thickness of clouds increases, scattering becomes more significant, but when raindrop sizes increase at the base of the cloud, the light absorption overtakes the scattering.
However, it seems the question is trying to get at the idea of why might there seem to be more light present. Below are various reasons and situations where you might think there is more light when it rains:
Understanding the Perception of a Brighter Sky
The sensation of a brighter sky when it's raining is usually due to other factors, often related to the conditions before or during rain:
- Light Reflection and Refraction:
- Raindrops and wet surfaces can act as reflectors, bouncing light from nearby artificial sources, such as streetlights, or even the moon, which can then make areas seem brighter.
- When light passes through raindrops, it refracts (bends), and this can also contribute to a perceived increase in light intensity.
- Cloud Cover and Artificial Light:
- Before a rainstorm, clouds often become lower and thicker. These clouds, which are closer to the ground, can act as a diffuser for artificial light sources. The light is reflected off the clouds and spreads across the sky creating an overall "glow."
- This is an example of scattering mentioned in the reference. However, the key point from the reference is that larger raindrops absorb light.
- Before a rainstorm, clouds often become lower and thicker. These clouds, which are closer to the ground, can act as a diffuser for artificial light sources. The light is reflected off the clouds and spreads across the sky creating an overall "glow."
- Cleaned Atmosphere:
- Rain can wash away dust and pollutants from the atmosphere, which allows more light to travel through it with less scattering or absorption. This cleaned atmosphere might result in a slightly "brighter" view of distant light sources.
The Role of Light Absorption
Contrary to the common misconception of a "brighter" night sky, the reference highlights a very important principle:
- Absorption outweighs scattering: As stated in the reference, when droplets at the cloud base increase in size (e.g. before rain), light absorption becomes dominant. This is why a heavy downpour typically darkens the surroundings as the raindrops absorb more light.
In summary:
| Condition | Effect on Light |
|---|---|
| Before rain (thin clouds) | Light scattering increases |
| Before heavy rain (thick clouds) | Light scattering increases |
| During rain (large drops) | Light absorption increases |
| After rain (clean air) | Light transmission increases |
In conclusion, a feeling of a brighter sky during rain is often a result of the scattering of artificial light by the clouds or the effect of light interacting with the rain itself, rather than an actual increase in ambient natural light. It's more to do with perception and how different lighting scenarios interact with water. Actual ambient light is more often dimmed during rain events.
