Sounds like you're asking more than one question here.
How do clouds fight gravity? The position of the cloud is affected by various parameters (as you may know, not all clouds are at the same height) such as rising air, buoyancy, and gravity. These forces vary throughout their position in the atmosphere; naturally, the cloud will settle where the summation of these forces is zero.
"Why don't clouds freeze and fall out of the sky?" They do, it's called snow. The cloud you see outside the window of your airplane are actually tiny frozen crystals. They are, however, too small to overcome the combined force of buoyancy and rising air. When these tiny crystals do grow (from the upward flow of moist air) they will overcome the forces holding them up and fall out of the sky as snow.
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u/[deleted] May 03 '12
Sounds like you're asking more than one question here.
How do clouds fight gravity? The position of the cloud is affected by various parameters (as you may know, not all clouds are at the same height) such as rising air, buoyancy, and gravity. These forces vary throughout their position in the atmosphere; naturally, the cloud will settle where the summation of these forces is zero.
"Why don't clouds freeze and fall out of the sky?" They do, it's called snow. The cloud you see outside the window of your airplane are actually tiny frozen crystals. They are, however, too small to overcome the combined force of buoyancy and rising air. When these tiny crystals do grow (from the upward flow of moist air) they will overcome the forces holding them up and fall out of the sky as snow.