Dear Tom,
My friends and I at school would like to know what keeps clouds up. Why don’t they fall like raindrops?
Jonathan Childers
Dear Jonathan,
The innumerable clouds that drift across the sky above our heads are composed of tiny water droplets or ice crystals and those particles, responding to the downward tug of gravity, actually do fall through the air, but very slowly. They are kept aloft by air that is slowly rising.
Cloud particles fall so slowly that only very slightly rising air is required to keep them aloft. For most cloud droplets, for example, air rising at only 0.02 m.p.h. is sufficient to provide the necessary lift.
Cloud droplets are incredibly tiny–they average only about 0.000039 inch in diameter–and at that size it takes over one million of them to make an average-sized raindrop.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN-TV News at noon and 9 p.m.
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or asktomwhy@wgntv.com (Mail volume precludes personal response.)
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
