Hi, Jasen.  I overheard you and Leonard talking about - -

-=> JASEN BETTS wrote to LEONARD ERICKSON <=-

 JB> 07-Jul-03 03:54:03, Leonard Erickson wrote to Phil Marlowe

 PM>> And what exactly are inversion layers?

 LE> Layer of warm air acting as a "cap" over a layer of cooler air.

 JB> actually it's the inverse of that.

Nope.  See one explanation below.  There is a much better one at

http://daphne.palomar.edu/calenvironment/smog.htm

and that one also goes into more specifics about different ways
inversion layers are formed, with some specifics about conditions in
California.  It had some embedded html stuff, so I didn't try to
download and clean the HTM code out of there.

 JB> Air temperatuure normally decreases with altitude (because gravity
 JB> slows down the air particles)

Nope again - warmer matter has faster-moving molecules than colder
matter.  BIR from chemistry class, temperature of matter is a
proportional measure of the average kinetic energy of its molecules.

 JB> an inversion layer occurs wheen warm air
 JB> gets trapped under a layer of cold air.  

But, as you said above, warmer air on bottom is the norm.  But, at the
same atmospheric pressure, the warmer air always tends to rise, due to
its lower density.

- - -  JimH.
  *************************

Temperature inversion - WikipediaTemperature inversion
From Wikipedia, the free encyclopedia.

"Under normal circumstances, the air near the surface of
the Earth is warmer than the air above it.

"Typically air is hottest at the ground. Air is fairly
transparent to sunlight, most of which passes straight
through it without heating it. When the sunlight
reaches the ground it is almost entirely absorbed,
heating the land. Some of this energy is then re-radiated
as blackbody radiation, and due to the average temperatures
involved, much of this is in the infrared.
Unlike the original sunlight, infrared light interacts
more strongly with air, which is then heated from below.

"Hot air, however, rises. This leads to constant convection
which draws the warmer air up, to be replaced with cooler
air which is then heated. It is this process that leads
to cloud building, thermals, and other convection related
atmospheric behaviour.

"However, it is sometimes possible to find situations where
the gradient is inverted, so that the air gets actually
colder as you approach the surface of the Earth. This is
called a temperature inversion. It is most commonly created
by the movement of air masses of different temperature
moving over each other. A warm air mass moving over a
colder one can "shut off" the convection effects, keeping
the cooler air mass trapped below. (see capping inversion)

"With the disruption of normal convection, a number of
phemoninon are associated with a temperature inversion.
One common effect is the general "stillness" of
the air, as is dirty or foggy air which can no longer be
pulled away from the surface.

"The index of refraction of air decreases as the air
temperature increases, a side effect of hotter air being
less dense. Normally this results in distant objects being
shortened vertically, an effect that is easy to see at
sunset (where the sun is "squished" into an orb).In an
inversion the normal pattern is reversed, and distant
objects are instead streched out or appear to be above
the horizon. This leads to the interesting optical effects
of Fata Morgana or mirage.

"Similarly, radio (being light) can be re-directed by such
inversions. This is why it is not uncommon to hear radio
(and sometimes TV) broadcasts from seemingly "impossible"
distances on foggy nights. The signal, still more than
powerful enough to receive even at hundreds or thousands
of miles, would would normally be refracted up and away
from the ground-based antenna, but is now refracted back
down instead."

Retrieved from
"http://www.wikipedia.org/w/wiki.phtml?title=Temperature_inversion"
This page was last modified 13:27 27 Jun 2003.

... Jim, I only got 2 parts of me getting bigger - earlobes and belly- Bubba
--- MultiMail/MS-DOS v0.32