What causes clouds to appear large and bulbous?


Title. What phenomena causes them to take these large “fluffy” looking shapes? Is it just how water particles act in the atmosphere?

In: Chemistry

Many clouds (i.e. thunderstorm supercells and ice clouds) aren’t fluffy at all.

But we’ll ignore them for a moment and talk about those weird white ones. Those are made of water droplets ([sort of](https://www.youtube.com/watch?v=8lBvC7aFB40)), and heat from the ground causes them to stay aloft. They have to meet a sort of balance between the up force of ground heat and the down force of gravity. This will happen in different places for different sizes of drop. Plus, they won’t all form in the same place–they’ll be separated side to side too. So the cloud now looks sort of blobby. It doesn’t help that wind directions high up the atmosphere can change direction either, which pushes and pulls the cloud into different shapes.

One other big factor in cloud shape is how hot and cold air are moving through a region. This actually brings us back to supercells; they form when hot air gets trapped under cold air, they mix, and start to rotate. Water condenses where they’re mixing as well, so the whole storm starts rotating. And that’s where baby tornados come from.

src: I’m a physicist, so I’m pretty sure about most of this stuff (plus I grew up in a heavy-tornado area), but if any meteorologists weigh in, I’d trust them more.

Those clouds, called cumulus, forms from air particles rising to a certain point where they then begin to cool. At the temperatures it cools to, these can cause the relative humidity of the area to reach 100%. Then, as the RH is 100%, water vapor condenses and releases heat. This is a feedback loop, causing big clouds to form. Water condenses onto any particles in the air, and as the feedback loop continues, the cloud will “puff” up, and eventually become so moisture laden as to rain.