Weird, Rare Clouds and the Physics Behind Them
These crazy clouds that look like a row of crashing waves are known as Kelvin-Helmholz waves. They form when two layers of air or liquid of different densities move past each other at different speeds, creating shearing at the boundary.
“It could be like oil and vinegar,” Chuang said. “In the ocean, the top is warm and the bottom is really cold. It’s like a thin layer of oil on a big puddle of water.”
When these two layers move past each other, a Kelvin-Helmholz instability is formed that is sort of like a wave. Parts of the boundary move up and parts move down. Because one layer is moving faster than the other, the shear causes the tops of the waves to move horizontally, forming what looks like an ocean wave crashing on the beach.
“It really is like breaking waves,” Chuang said. “A wave breaks when the water on top moves so much faster than the water below that it kind of piles up on itself.”