Re: What holds clouds together? Why don't they dissipate?

Clouds aren't really held together by anything.  A cloud entering
dry air WILL dissipate.  The fact that clouds are in single pieces is 
because of the way that they form.  When warm, moist air enters an area of
cool air, it cools down.  When it cools down it can hold less moisture.  
The moisture begins to condense, and you have a cloud.  The edge of a cloud
is simply the edge of what used to be the warm air.  When the air around a
cloud can hold more moisture than it already has, the cloud will evaporate.
Have you ever seen a day when the edge of the clouds is fuzzy?  Those 
clouds are evaporating.  On a day when the edge of the cloud is sharp, the 
cloud is still forming.  As long as the air around a cloud is at 100% 
humidity, the cloud will not evaporate.  

Wind, blowing in different directions at different levels, can also shear a 
cloud into pieces.  If you ever see a cloud from a thunderstorm, the cloud 
will probably be shaped like an anvil.  The reason for the top of the cloud 
being stretched out is that the top of the cloud extends to another layer 
of the atmosphere where winds blow very quickly.  Sometimes the bottom of 
the cloud will be blown off, too.  Meteorologists call this phenomenon 
"Beaver tail" because, from the ground, the clouds blown off the bottom of 
the storm look like, you guessed it, a beaver's tail.
Another windblown cloud is the cirrus cloud.  These are thin whisps of 
cloud blown off the tops of high clouds.

In summary, the reason why you see a cloud as one piece is because it 
formed that way.

Thanks, and keep those questions coming!
                         Matthew Barchok, Mad Scinetist