GREENVILLE, N.C. (WNCT) — Have you ever wondered why rain and storm clouds appear grey rather than the usual white? It has a lot to do with how our eyes perceive sunlight as it interacts with particles in the atmosphere.
In order for a cloud to form, there must be rising moist air present. When a batch of warm air rises, it moves into cooler air. When this occurs, the particles expand, still containing moisture. As they expand, a basic cloud forms. Clouds grow in height and shape when the cooling continues and ice particles form.
So, where does color come into play? Sunlight shining down on Earth is actually made of all colors, but from our eyes’ perspective, all those colors meshed together look white. When sunlight interacts with particles, different colors are seen throughout the atmosphere, like our blue sky for instance.
When sunlight passes through a cloud, the particles are closely knit together and scatter out all colors, which just appear as white. This changes with a growing storm. When a cloud grows in height, sunlight has a further distance to travel through the cloud but is still scattered out along the way.
Less sunlight makes it to the bottom of the cloud, which is why our eyes perceive the cloud color as gray rather than white.
As the cloud turns grey, those particles of water vapor begin to clump together forming raindrops, and then well it rains. Now you know why some clouds are grey while most clouds are white.