How do clouds stay up?

29 July 2007

Question

I have heard that high level clouds are composed of ice crystals and mid level clouds are mainly water droplets, how are the ice crystals and the water droplets held up in the clouds if ice and water are denser than air?

Answer

The droplets in clouds are very small things, only about 20microns or 0.02mm in size so it only takes a very small updraght to keep those droplets suspended in the atmosphere. Raindrops are above about 2mm so about 1,000,000 cloud droplets. When they are big enough to overcome the updraught they will fall down to earth as rain.

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