Re: What keeps clouds up?

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

> A description of cloud formation and of the processes that take place within
> clouds can be found in any good meteorology text. I recommend F. K. Lutgens and
> E. J. Tarbuck, THE ATMOSPHERE (Prentice-Hall).
>
> As an instrument-rated pilot who has seen the inside of quite a few clouds
> (though not as many as I would like!), I can attest that many clouds are quite
> smooth inside, with nary an updraft or downdraft to be found. But cumulus
clouds
> typically have both updrafts and downdrafts within them. A long out-of-print
> book by W. H. Rankin (THE MAN WHO RODE THE THUNDER, Prentice-Hall, 1960)
> describes the author's harrowing experience when he had to bail out of his
> Marine jet fighter at 47,000 feet --- into an active thunderstorm. He spent
over
> half an hour going up and down in the vertical circulation, hanging on to his
> parachute for dear life! See if your library has this book --- it's quite a
> read.
>
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>
> Roger A. Freedman
> Dept. of Physics and College of Creative Studies
> University of California, Santa Barbara

As an aside, I actually prefer METEOROLOGY TODAY by C. Donald Ahrens for a
good meteorology text. 

There is a High Plains Chapter of the AMS/NWS made up of meteorologists from
Kansas and Nebraska which meets here quarterly. Last spring one of the
fellows involved in cloud seeding reported to the group that he flew his
light plane in the updraft near the base of a cumulonimbus cloud for one
hour and 20 minutes without power. (He powered down all avionics that were
not necessary to conserve the battery.) His concern was starting the engine
after this time in -40 F temperatures. He reported that the engine started
immediately, and he didn't have to resort to his alternative. 

Silver iodide is released near the base of these clouds and is drawn into
the cloud by the strong updrafts. Dry ice is released higher up in the
cloud. The intent is to reduce hail formation. No one really knows if cloud
seeding works to reduce or eliminate hail because there are no controls
possible. Each storm is different and while cumulonimbus clouds may appear
outwardly similar they can be extremely different in internal details.

When talking about updrafts we need to be specific about the type of clouds
we are talking about. In warm stratus clouds the updrafts are about 10 cm/s.
In a thunderstorm (cumulonimbus cloud), updrafts have been measured in
excess of 25 m/s (56 mi/hr).

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