Re: Hot air rising

[Leigh Palmer <palmer@SFU.CA>]

At 2:02 PM -0700 7/21/99, Robert A Cohen wrote:
> On Wed, 21 Jul 1999, Leigh Palmer wrote:
>
> > Students often see physics as an exercise in studying a nonexistent
> > universe. Their belief is that physics does not model the world they
> > live in. Models that fail even the simple test of casual observation
> > should be avoided! Simple physics doesn't explain everything. Even
> > our complete physics cannot yet explain everything; indeed physics
> > is incomplete. We should let on to our students that we know this.
> > The real atmosphere problem is complicated. Any explanation of it
> > should be heavily posted with caveats.
>
> When the atmosphere is well-mixed (oops, I mean "characterized by
> large-scale vertical exchanges of air such that conservative properties
> are equalized"), the vertical temperature profile is observed to be
> adiabatic.  See yesterday evening's sounding at Topeka, for example
> (adiabatic from surface to about 1.8 km or so).  A simple model (as far as
> I can tell) that is explained by a casual observation.

You miss my point. The casual observation to which I refer is that the
temperature varies as measured by my thermometer as I climb the mountain.
In the case I cited it rises, reflecting a real temperature inversion.
I can't parse your last sentence otherwise than to infer you thought I
said that one explains things *by* casual observation. Flying a radio-
sonde is not a casual observation, if that's what you intended here. I
want students to understand what they perceive in the everyday world
around them which, in this era, includes thermometers on cars. It will
soon include such things as GPS receivers, and when it does I will want
my students to understand them, too. I have taught my interested majors
how color TV works (including the psychophysics, colorimetry, and NTSC
frequency interlace multiplexing). Color TV is easier to understand
than, say, climate!

You should add to your qualification "well-mixed" the qualification
"and unsaturated". Latent heat* will play no role in that case, and
the adiabatic model is appropriate.

Leigh

*Yes, I know it's a noun here, but the noun has conventional meaning
when modified by the adjective "latent". Consider "latent heat" to be
an inseparable noun phrase, eh?