Re: What keeps clouds up?

[PHRP@FHSUVM.FHSU.EDU (Roger A. Pruitt)]

> On Sat, 22 Mar 1997, Fred Bucheit wrote:
>
> > When water evaporates from a water droplet it does not add mass to the
> > atmosphere, it displaces air thereby making the air lighter. Diatomic
> > nitrogen has an atomic mass of 28 and diatomic oxygen has an atomic mass of
> > 32 but a water molecule has a mass of 18.
> > Humid air is less dense than dry air and therefore tends to rise in the
> > atmosphere.
>
> Ah, that helps.  I didn't know how to visualize evaporated water as
> compared to nitrogen.  So, in simple language, water vapor acts more like
> He than like CO2.
>
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For this reason a cubic meter of humid air is less dense than a cubic meter
of dry air. 

Roger

Roger A. Pruitt, PhD
Professor of Physics
Fort Hays State University
Hays, KS  67601