wrote in message
...
On Fri, 26 Nov 2004 17:53:01 GMT, "Mike Rapoport"
wrote:


"Andrew Sarangan" wrote in message
.61...
Ah, I see what you are getting at. But I never said stability is only
determined by adiabatic lapse rate. The difference between the
environmental lapse rate and the adiabatic lapse rate is what determines
the stability. The average adiabatic lapse rate is 2C/1000' but can vary
based on moisture. Therefore, if the environmental lapse rate is higher
than 2C/1000' that atmosphere can be considered to be unstable.

Absolutely not! If the air is unsaturated and the lapse rate is 2C/1000
but
below 3C/1000, then the air is absolutely, totally stable! No "ifs",
"ands", or "buts", it is stable. It cannot be considered to be unstable.


If the air is unsturated, it will cool at the dry adiabatic lapse
rate. If it becomes saturatede, it will cool at the moist adiabatic
lapse rate. This alone has nothing to do with stabiity.

If the environmental lapse rate is greater (superadiabatic), the
atmosphere will be unstable (the parcel will rise). If the
environmental lapse rate is less than the adiabatic lapse rate, the
air will be stable. The parcel will not rise (an it might even sink).


Isn't that what I just said?

Mike
MU-2


For a
moist parcel of air 2C/1000 environmental lapse rate will be unstable,
but for a dry parcel of air it will be stable.

Yes! but this is in direct contradiction to your above statement
"Therefore, if the environmental lapse rate is higher
than 2C/1000' that atmosphere can be considered to be unstable."

Mike
MU-2

wrote in
:



Adiabatic lapse rates (there are more than one) are theoretical and
calculated.

The calculations do not change from day to day.

The dry adiabatic lapse rate witll be calculated tomorrow the same way
it is today. It measures a physical process, i.e., the amount of heat
given up as air rises and expands,

Therefore it does not, as you suggest, indicate stability or
instability, since it will be the same in unstable air as it is in
stable air.

It is the ;lapse rate of the surrounding air that determines
stability, not the lapse rate of the rising air, which is the same
every day, day in and day out.