Re: Hot air rising and automobile thermometers

[Leigh Palmer <palmer@SFU.CA>]

At 16:24 -0700 7/23/99, brian whatcott wrote:
...

> We could visualise an ordinary wind as flowing nearly parallel to
> lines of equal atmospheric pressure ('isobars') across a plane surface
> and motivated by the pressure gradient between them.

...

> As to the reason for naming the temperature-driven winds (as opposed
> to the pressure-driven common wind) I suppose one should consult
> Xenophon's description of the uphill march of Cyrus' son into Asia.
> It was the prototype anabasis. Katabasis was the Greek word
> for going down.

The "common wind" referred to here is called the "geostrophic" wind.
Explaining why it flows parallel to the isobars when driven by the
pressure gradient is a good exercise for the physicist, unless his
religion forbids belief in the Coriolis force. It also gives new
meaning to the term "equilibrium". (The equilibrium is established
between the pressure gradient force and the Coriolis force in the
frame of reference which moves with the wind.)

Leigh