When it comes to the color of the sky, people will think of blue. When we think of the color of clouds, people think of white. Then why are dark clouds grey? Is there any scientific basis for these stereotypes? What are some of the principles behind this?

There are different colors of clouds in the sky, some are very white, and some are very black. Clouds are made up of tiny water droplets and ice grains.

Clouds appear white because they scatter the sunlight that falls on them. At the same time, a lot of sunlight filtered through the clouds, making the clouds appear bright.

In fact, dark clouds are not strictly a classification of clouds! What we call dark clouds is actually only distinguishable from the color, and the color of the cloud is just a little joke of the light.

When the sun passes through the clouds, the small water beads in the cloud will reflect and scatter the light. The light from the clouds will be weakened to varying degrees. Therefore, the water vapor gathering state in the cloud layer and the thickness of the cloud layer will directly affect the black-and-white level of the cloud.

When the weather is good, the water droplets combined with water vapor are smaller, and the light through the light is mostly scattered. Even if the clouds are thicker at this time, the impact on light is not great, so the cloud looks white or gray.

Dark clouds are the source of rain. When they accumulate to a certain thickness and weight, rain is formed. In the early stage of raindrop formation, cloud droplets mainly rely on continuous absorption of water vapor around the cloud body to condense, so that the surface of the cloud droplets is often in a saturated state. Then in the process, the cloud droplets grow and become raindrops.

After the rain, the air becomes less humid and the water vapor returns to its unsaturated state. At this point, the small water droplets in the cloud begin to evaporate and become smaller and smaller, and then the cloud becomes white. If the droplets in the white cloud continue to evaporate, once they have all vaporized, the white cloud is gone.

The color of a cloud is also related to its thickness. Clouds appear white because they are so thin that it is easy for the sun's light to fall in and appear white. The thickness of the cloud determines the color.

When you encounter thick stratiform or cumulonimbus clouds, the sun and moon have a hard time getting through, and the clouds appear dark. The thinner stratiform and undulate clouds appear lighter and gray. For this reason, clouds on cloudy days are gray.