Cloud shapes

Tyro

What causes the high up cirrus clouds to be ripple shaped and thin, while the lower stratus or cumulo nimbus clouds to be puffy and opaque?

Presumably, it must have something to do with atmospheric density and temperature...although how exactly seems uncertain.

Also, what causes clouds to congregate into visible structures? Why don't they just dissipate/diffuse like a gas or smoke in another? What holds clouds together?

FZ+

I think a major factor in this is that the higher clouds are composed of ice, while the lower down clouds, being warmer, are made up of water droplets...

Tyro

So is it correct to say that since the density of ice is the lower than the density of water, the greater obscurity of low altitude clouds is a result of diffraction (due to smaller particle diameters) while at high altitudes it is the result of absorption?

How do you explain the irregular shapes of clouds? Why doesn't the atmosphere just look like muddy water (i.e. the clouds just disperse into a homogeneous, featureless, mass)?

russ_watters

High cirrus clouds are lower density as stated, but remember, they aren't a solid block of ice. They are MUCH lower density than clouds at low altitude for two reasons: One, the density of the atmosphere itself is many times (10x or so, probably) thinner at the altitude of cirrus clouds. And two, at lower temperature, the air holds far less water than at high temperature.

LURCH

One thing I've noticed when travellingn in a small aircraft is that the atmosphere itself is not smooth. Pockets of verying air-density can actually be felt as one flies through them. This "bumpy air" is especially noticable at the edges of clouds. I don't know what other factors are involved, but this change in density itself would be enough to cause condensation to occurr.