What you described is exactly the point many people (including myself)
have been confused about. The 2C/1000' is the average environmental
lapse rate. Adiabatic lapse rate is never 2C/1000'. It is 1C/1000' or
3C/1000'. Many FAA texts do not explain this point clearly. Since most
pilots get their meterology knowledge from FAA texts, and are not
formally educated on the subject, it is not surprising this confusion
exists. I would bet you any money that if you took a survey of CFI's
most would not know this fact.


"Icebound" wrote in
:




"Darrell S" wrote in message
news:bdUNd.46622$bu.24635@fed1read06...
2°/1000' is "average" since air at different levels may be saturated
or unsaturated and can change from one to the other
at different levels. Lifted air would cool at 3°/1000' while
lifting through dry air and at 1°/1000' lifting through moist air
levels. So.... the average is 1°


no, No, NO!!!

The 2 degrees per 1000 feet comes from a "determined" average lapse
rate of real atmospheres averaged around the globe and averaged
throughout time.... determined within reason. It has nothing,
NOTHING, to do with saturated or unsaturated or dry adiabatic or
saturated adiabatic. Dry and Saturated adiabatic lapse rates are a
law-of-physics-rates-of-cooling, not actual temperatures in the real
nor in the "standard" atmosphere.

Please divorce those two concepts:

First concept:
Environmental lapse rate: temperature structure of the real
atmosphere right now. Usually, but not necessarily, cools with
height. How much per 1000 feet? Depends on the structure TODAY, THIS
INSTANT. Not constant throughout. May be several degrees per 1000
feet in some layers, zero in others, and even an inversion in still
others.

... and Standard Atmosphere Lapse Rate: defined at "lowering 1.98
degrees per 1000 feet" within the troposphere (lowest 11 kilometres).

Second concept:
Dry Adiabatic lapse rate: a RATE-OF-COOLING (or heating) of a parcel
of air should it be displaced from its present level and rise (or
descend) through the atmosphere, with the consequent pressure change
on it. The "dry-adiabatic" rate of cooling will occur as long as no
moisture is being condensed. About 3 degrees per 1000 feet,
reasonably linear with height.

... and Saturated Adiabatic lapse rate: a RATE-OF-COOLING (or heating)
of a parcel of air should it be displaced from its present level and
rise (or descend) through the atmosphere, with the consequent pressure
change on it. The "wet-adiabatic" rate of cooling (or heating) will
occur as long as the relative humidity of the parcel is 100 percent
and moisture is being condensed (or evaporated if descending). This
rate is less than the dry-adiabatic rate, because the condensation of
moisture releases heat which slows the cooling of the air. Not linear
with height. Varies from about 1 degrees per 1000 feet at very high
dewpoints, to almost 3 degrees per 1000 feet at very low dewpoints.

Two different concepts!