On 26 Nov 2004 09:53:14 -0600, Andrew Sarangan
wrote:


That's interesting, but I find it strange that moisture content does not
change the adiabatic lapse rate. Moist air has a higher heat capacity than
dry air, so I would expect the adiabatic lapse rate of moist air (but
unsaturated) to be lower than dry air.


It is. But the additional heat comes from the process of
condensation, not expansion.

So the moist adiabatic lapse rate is a combination of two things,
cooling by expansion, and heating by condensation.





"Julian Scarfe" wrote in
:

"Andrew Sarangan" wrote in message
om...

Adiabatic lapse rate is 1C/1"Hg for moist air (depending on moisture
content) and 3C/1"Hg for dry air. 2C/1"Hg is a representative average
for somewhat moist but unsaturated air.

No, moist but unsaturated air has an adiabatic lapse rate of 3 degC
(i.e. the unsaturated adiabatic lapse rate). The difference between
that and saturated comes not from the amount of water vapor in the air
as a mixing of properties, but from the latent heat produced when the
water vapor condenses, which only happens when the air becomes
saturated. It's not a progression, but a sharp difference when the
water vapor starts to condense.

Julian Scarfe