Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site maxvax.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!drutx!mtuxo!pegasus!maxvax!wfl From: wfl@maxvax.UUCP (w linke) Newsgroups: net.aviation,net.astro Subject: Re: Something else to watch out for! Message-ID: <186@maxvax.UUCP> Date: Tue, 25-Jun-85 17:23:43 EDT Article-I.D.: maxvax.186 Posted: Tue Jun 25 17:23:43 1985 Date-Received: Wed, 26-Jun-85 07:18:23 EDT References: <11270@brl-tgr.ARPA> <1199@phoenix.UUCP> <1679@amdahl.UUCP> <122@shell.UUCP>, <377@iham1.UUCP> Organization: AT&T Information Systems, Holmdel NJ Lines: 43 Xref: watmath net.aviation:1680 net.astro:693 [] >> > I can't imagine how hitting a cloud layer - no matter how >> > dense - would be like hitting the ground (even at meteoric speeds). >> >> I remember from ground school that air filled with water vapor is >> less dense than dry air, even though is feels "heavy". If clouds >> are water vapor, doesn't this make them *less* dense than the >> surrounding air? Unless there was a storm in progess with >> condensed water, I guess. >> >> A. Lester Buck >> {ihnp4, pur-ee, ut-sally}!shell!buck > >Clouds aren't made of water vapor. They are made of minuscule water droplets. >Don't forget that water vapor is invisible. You begin to see clouds when >vapor-laden air rises to a point where it's cool enough for the vapor to >condense. > >You're right that moisture-laden air is less dense than dry air. The picture >changes when the water vapor condenses. Then you've got a bunch of droplets >hanging around, and that's a heck of a lot of mass for a meteor to try to >push out of the way. Don't forget that water (and air, if you're going fast >enough) is incompressible. > > John Opalko > AT&T Bell Labs > Naperville, IL > ihnp4!iham1!jgpo If you identify a parcel of air in the atmosphere, and follow it as it enters a region of temperature/pressure such that its water vapor condenses, it will become a cloud; yet the mass of the parcel has not changed! Which is another way of saying that clouds are not something *added* to the atmosphere, and the mass of air to be moved is not different if the water is distributed as microscopic drops instead of as gas. But before this discussion gets too far out of sight, may I ask if anyone on the net can cite any references for the original posting? If I remember correctly, it was just hearsay about some Japanese airliner that had to avoid a rapidly-forming cloud. Sounds like the National Enquirer to me. W. F. Linke