Atmospheric stability and lapse rate

[Andrew Sarangan]

Instability produces cumulus clouds and stability produces stratus clouds.
We know that. However, since the saturated and unsaturated lapse rates are
significantly different (1C/1000' compared to 3C/1000'), it seems quite
possible to get cumulus clouds even when the atmosphere below is stable.
For instance, if the environmental lapse rate is 2C/1000', the unsaturated
air is stable. Once clouds form (how they form without vertical currents is
a different matter), the air inside the clouds will become unstable. Does
this seem reasonable?

On a related question, where does the concept of 'average' lapse rate
(2C/1000') come from? I always took this to mean 50% RH air, but it took me
a long time to learn that that was not the case. The air is saturated or it
is unsaturated. How can there be an average between saturated and
unsaturated? The standard lapse rate and standard temperature at
different elevations are all based on this 2C/1000' concept. What's the
deal with this?

[Mike Rapoport]

"Andrew Sarangan" > wrote in message
1...
> Instability produces cumulus clouds and stability produces stratus clouds.
> We know that. However, since the saturated and unsaturated lapse rates are
> significantly different (1C/1000' compared to 3C/1000'), it seems quite
> possible to get cumulus clouds even when the atmosphere below is stable.
> For instance, if the environmental lapse rate is 2C/1000', the unsaturated
> air is stable. Once clouds form (how they form without vertical currents
> is
> a different matter), the air inside the clouds will become unstable. Does
> this seem reasonable?
>
Yes are often a combination of clouds at various levels


> On a related question, where does the concept of 'average' lapse rate
> (2C/1000') come from? I always took this to mean 50% RH air, but it took
> me
> a long time to learn that that was not the case. The air is saturated or
> it
> is unsaturated. How can there be an average between saturated and
> unsaturated? The standard lapse rate and standard temperature at
> different elevations are all based on this 2C/1000' concept. What's the
> deal with this?
>
The 2C/1000 was arbitrarily chosen as the "standard" for things like
calibrating altimeters. As you note, it has nothing to do with the real
world.

Mike
MU-2

[jim rosinski]

Andrew Sarangan wrote:

> Instability produces cumulus clouds and stability produces stratus
> clouds.

Better to say "can result in" rather than "produces". That's because in
addition to atmospheric lapse rate characteristics, moisture content of
the air also determines when and where clouds will form. Many stable
situations actually act to dissipate clouds.

> We know that. However, since the saturated and unsaturated lapse
> rates are significantly different (1C/1000' compared to 3C/1000'),
> it seems quite possible to get cumulus clouds even when the
> atmosphere below is stable. For instance, if the environmental
> lapse rate is 2C/1000', the unsaturated air is stable. Once clouds
> form (how they form without vertical currents is a different matter),
> the air inside the clouds will become unstable. Does this seem
> reasonable?

Almost. The formation of a cumulus cloud is already an indication that
some localized instability has occurred. After the cloud has formed, it
is more likelly to remain unstable because the air within it is
saturated, and will cool at a slower rate as it rises than will
unsaturated air. This is due to the latent heat released by additional
droplet formation as the cloud grows.

> On a related question, where does the concept of 'average' lapse rate
> (2C/1000') come from? I always took this to mean 50% RH air, but it
> took me a long time to learn that that was not the case. The air is
> saturated or it is unsaturated. How can there be an average between
> saturated and unsaturated? The standard lapse rate and standard
> temperature at different elevations are all based on this 2C/1000'
> concept. What's the deal with this?

It really is just what you said at the start of your paragraph: an
average lapse rate. Observed lapse rates will vary all over the map,
sometimes greater, sometimes less than the average. Sometimes lapse
rates can go negative, which results in an inversion (warm air over
cold). What they won't do is exceed the dry adiabatic rate (the
3C/1000' you mentioned). This is because instability will result, and
convective overturning will restore the lapse rate to dry adiabatic.

An excellent introductory text explaining these issues is "Atmospheric
Science, an Introductory Survey", by Wallace and Hobbs. It's written
for a 2nd semester atmospheric science student, but is very readable.

Jim Rosinski

[Denny]

There was an inversion over Michigan the past few days... On both
Friday afternoon and Saturday, the temperature at 3500 feet was 5
degrees warmer than on the ramp... I didn't remember to note the
temperature change on Sunday, but the conditions were the same...

Denny

[Corky Scott]

On 6 Feb 2005 21:19:53 -0600, Andrew Sarangan
> wrote:

>Instability produces cumulus clouds and stability produces stratus clouds.
>We know that. However, since the saturated and unsaturated lapse rates are
>significantly different (1C/1000' compared to 3C/1000'), it seems quite
>possible to get cumulus clouds even when the atmosphere below is stable.
>For instance, if the environmental lapse rate is 2C/1000', the unsaturated
>air is stable. Once clouds form (how they form without vertical currents is
>a different matter), the air inside the clouds will become unstable. Does
>this seem reasonable?
>
>On a related question, where does the concept of 'average' lapse rate
>(2C/1000') come from? I always took this to mean 50% RH air, but it took me
>a long time to learn that that was not the case. The air is saturated or it
>is unsaturated. How can there be an average between saturated and
>unsaturated? The standard lapse rate and standard temperature at
>different elevations are all based on this 2C/1000' concept. What's the
>deal with this?
>

Regarding the "lapse rate", I've always been curious as to how knowing
about such a thing is useful while flying. I recall reading about it
while studying for the written and wondering how on earth I'd make use
of such information **IF** I could memorize it.

Do you fly around getting temperature readings at various locations
and start working the formula or do you just keep it in the back of
your head as something interesting (or not) and stear clear of the
clouds?

Thanks, Corky Scott

[Mike Rapoport]

It is not really useful for actually flying, but it is useful for
understanding the fundemental forces that drive weather.

Mike
MU-2


"Corky Scott" > wrote in message
...
> On 6 Feb 2005 21:19:53 -0600, Andrew Sarangan
> > wrote:
>
>>Instability produces cumulus clouds and stability produces stratus clouds.
>>We know that. However, since the saturated and unsaturated lapse rates are
>>significantly different (1C/1000' compared to 3C/1000'), it seems quite
>>possible to get cumulus clouds even when the atmosphere below is stable.
>>For instance, if the environmental lapse rate is 2C/1000', the unsaturated
>>air is stable. Once clouds form (how they form without vertical currents
>>is
>>a different matter), the air inside the clouds will become unstable. Does
>>this seem reasonable?
>>
>>On a related question, where does the concept of 'average' lapse rate
>>(2C/1000') come from? I always took this to mean 50% RH air, but it took
>>me
>>a long time to learn that that was not the case. The air is saturated or
>>it
>>is unsaturated. How can there be an average between saturated and
>>unsaturated? The standard lapse rate and standard temperature at
>>different elevations are all based on this 2C/1000' concept. What's the
>>deal with this?
>>
>
> Regarding the "lapse rate", I've always been curious as to how knowing
> about such a thing is useful while flying. I recall reading about it
> while studying for the written and wondering how on earth I'd make use
> of such information **IF** I could memorize it.
>
> Do you fly around getting temperature readings at various locations
> and start working the formula or do you just keep it in the back of
> your head as something interesting (or not) and stear clear of the
> clouds?
>
> Thanks, Corky Scott

[jim rosinski]

Andrew Sarangan wrote:

> On a related question, where does the concept of 'average' lapse rate
> (2C/1000') come from? I always took this to mean 50% RH air, but it
> took me a long time to learn that that was not the case. The air is
> saturated or it is unsaturated. How can there be an average between
> saturated and unsaturated?

Just realized that my last response didn't fully answer your question.
Lapse rate and moisture content are only loosely related--they are not
inextricably linked. It is possible to have moist air (at or near 100%
relative humidity) in one location with a steeper lapse rate than dry
air at another location. An inversion in dry conditions is just such a
situation.

One thing that CAN be said about the relation between lapse rate and
moisture content: unsaturated air can accomodate a steeper lapse rate
(up to the dry adiabatic rate of around 3C/1000') than can saturated
air. Saturated lapse rates can only reach saturated adiabatic values,
which are less than 3C/1000'. Actual saturated adiabatic lapse rates
are nonlinear functions of temperature, with lower lapse rates for
higher temperatures. This is because warm air can hold more moisture
than cold air.

Hope this helps.

Jim Rosinski

[Icebound]

"Andrew Sarangan" > wrote in message
1...
> Instability produces cumulus clouds and stability produces stratus clouds.
> We know that. However, since the saturated and unsaturated lapse rates are
> significantly different (1C/1000' compared to 3C/1000'), it seems quite
> possible to get cumulus clouds even when the atmosphere below is stable.
> For instance, if the environmental lapse rate is 2C/1000', the unsaturated
> air is stable. Once clouds form (how they form without vertical currents
> is
> a different matter), the air inside the clouds will become unstable. Does
> this seem reasonable?

Yes.

The most visible example of this situation is a relatively cloud-free day,
followed by severe thunderstorms along a passing cold front.

The warm air ahead of the front can be relatively "stable" and few or no
cumulus-type clouds form. Then when the cold front comes along and forces
the warm air upward, cooling it to saturation, suddenly the huge
cumulonimbus clouds erupt.... just because once saturated, the air is now
unstable.
>

> On a related question, where does the concept of 'average' lapse rate
> (2C/1000') come from? I always took this to mean 50% RH air, but it took
> me
> a long time to learn that that was not the case. The air is saturated or
> it
> is unsaturated. How can there be an average between saturated and
> unsaturated? The standard lapse rate and standard temperature at
> different elevations are all based on this 2C/1000' concept. What's the
> deal with this?
>
>

That is because the concept of "lapse rate" was taught to you badly.

There are the 4 different "lapse rates".

One answers the question: "What IS the temperature difference with height
in THIS airmass, as I travel up and down within it".

This is what you measure with your OAT as you travel. It is more correctly
known as the "environmental lapse rate"... in other words... the real lapse
rate in the real atmosphere as of right now.

Next one answers the question: What is the "average" condition of the
world's atmospheres throughout time, throughout the entire globe? Okay, not
exactly.... but if we could produce the specifications of an average like
that, then aircraft manufacturers can relate their performance specification
to "if you operate under these meteorological conditions". This became the
"ICAO Standard atmosphere", with the "standard" lapse rate of 1.98 degrees C
per 1000 feet (in the troposphere). It is a purely artificial "average"
that allows comparison against the real atmosphere, above.... if my aircraft
is supposed to perform like such in the "standard", then it will perform
like "so" in today's real life.

The third and forth lapse rates are of a totally different "type". Above,
we talked about "difference in temperature with height"... how one level is
different from another.

Now we talk about a "rate of cooling". This requires some background:
1. If we do not add or remove heat, then the temperature of air will lower
as the pressure lowers on that air.
2. Pressure lowers as we go up, as we all know, so we can translate
pressure decrease to altitude increase.
3. Condensation causes a release of heat... the reverse of evaporation
which requires an input of heat.

Therefore, if we raise a parcel of air in elevation (reduce its pressure),
and no condensation occurs, then the air will cool at some rate. If we
raise a parcel of air, and condensation DOES occur, then the released heat
will warm the air up a little and it will not cool as quickly.

Okay, back to the lapse rates:
The "dry adiabatic lapse rate" is not a difference in temperature with
height as are the "environmental" and "ICAO standard" lapse rates. It is,
instead, a rate of COOLING... the THEORETICAL change of temperature in a
parcel of air, IF that parcel were to rise. "dry adiabatic" mean no heat
added and no condensation occurring. This number has been experimentally
determined... it is an almost straight line value of approximately 3 degrees
C per 1000 feet.

Similarly the "moist (or saturated) adiabatic lapse rate" is the THEORETICAL
change in temperature in a parcel of air, if it were to rise WHILE
CONDENSATION WAS OCCURRING (and hence some heating of the air was
occurring). This number is NOT linear, because high-dewpoint air means way
more moisture condensing and way more heat being release.... so the cooling
may be only about 1 degree per 1000 feet with 30 deg C dewpoints, but nearly
3 degrees per 1000 at -30, because at minus 30 the amount of moisture in the
air is miniscule.


Remember, actual or "standard" change in temperature with height, versus a
known theoretical "rate of cooling" of a rising parcel. Two very different
things.

[jim rosinski]

Icebound's post is well-written and almost exactly accurate. Just one
quibble:

Icebound wrote:

> "dry adiabatic" mean no heat
> added and no condensation occurring. This number has been
> experimentally determined... it is an almost straight line
> value of approximately 3 degrees C per 1000 feet.

The dry adiabatic lapse rate is not an experimentally determined
number. It can be derived from equations, and turns out to be defined
by the remarkably simple expression: g/Cp, where g is gravity (9.8 m/s)
and Cp is the specific heat of dry air (1004 J/kg). Perhaps the
experimental nature you're referring to has to do with an "average"
moisture content which acts to change Cp slightly?

Jim Rosinski

[Darrell S]

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°

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

"Andrew Sarangan" > wrote in message 1...
> Instability produces cumulus clouds and stability produces stratus clouds.
> We know that. However, since the saturated and unsaturated lapse rates are
> significantly different (1C/1000' compared to 3C/1000'), it seems quite
> possible to get cumulus clouds even when the atmosphere below is stable.
> For instance, if the environmental lapse rate is 2C/1000', the unsaturated
> air is stable. Once clouds form (how they form without vertical currents is
> a different matter), the air inside the clouds will become unstable. Does
> this seem reasonable?
>
> On a related question, where does the concept of 'average' lapse rate
> (2C/1000') come from? I always took this to mean 50% RH air, but it took me
> a long time to learn that that was not the case. The air is saturated or it
> is unsaturated. How can there be an average between saturated and
> unsaturated? The standard lapse rate and standard temperature at
> different elevations are all based on this 2C/1000' concept. What's the
> deal with this?
>
>

[Icebound]

"jim rosinski" > wrote in message
ups.com...
> Icebound's post is well-written and almost exactly accurate. Just one
> quibble:
>
> Icebound wrote:
>
>> "dry adiabatic" mean no heat
>> added and no condensation occurring. This number has been
>> experimentally determined... it is an almost straight line
>> value of approximately 3 degrees C per 1000 feet.
>
> The dry adiabatic lapse rate is not an experimentally determined
> number.

I simply meant that it is a number which, one way or another, is
more-or-less known. It was a bit of a typo... "experimentally" should not
have been there, but I didn't want to say "theoretically", because I worried
pilots might think that the number is some kind of guess and not really
known.

Saying "Experimentally" didn't alter the gist of the post for pilots... only
for research-meteorologists! :-)

[jim rosinski]

I wrote:

> remarkably simple expression: g/Cp, where g is gravity (9.8 m/s)

This should have read 9.8 m/s^2, not 9.8 m/s, for those who care.

Jim Rosinski

[Icebound]

"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!

[jim rosinski]

Icebound wrote:

> Saying "Experimentally" didn't alter the gist of the post for
pilots... only
> for research-meteorologists! :-)

Agreed. I really am pleased to see this much interest, and frankly
knowledge, displayed by pilots for a subject I've spent a good part of
my life studying.

Jim Rosinski

[Andrew Sarangan]

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!
>
>
>

[jim rosinski]

Andrew Sarangan wrote:

> 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 don't want to re-confuse you, but there actually *is* a saturated
adiabatic lapse rate equal to 2C/1000'. Recall that warmer air can hold
more moisture than cold air. As a result, saturated adiabatic lapse
rates vary from nearly the same as the dry rate of 3C/1000' (cold air),
all the way up even beyond the 1C/1000' you quote (very warm air).

You're right about the ****-poor nature of FAA texts though. Not just
the bad meteorological explanations, even their basic physics is wrong.
They blather on about "centrifugal force", which doesn't even exist!
What does exist is centripetal acceleration, which acts in the opposite
direction of the mythical "centrifugal force".

Jim Rosinski

[Peter Duniho]

"jim rosinski" > wrote in message
oups.com...
> [...]
> You're right about the ****-poor nature of FAA texts though. Not just
> the bad meteorological explanations, even their basic physics is wrong.
> They blather on about "centrifugal force", which doesn't even exist!

Well, except that unlike the whole lapse rate confusion, the idea of
"centrifugal force" is perfectly valid, depending only on one's frame of
reference, and complained about only by overly pedantic engineers and
laymen.

Pete

[Joe Morris]

"Peter Duniho" > writes:

>"jim rosinski" > wrote:
>> [...]
>> You're right about the ****-poor nature of FAA texts though. Not just
>> the bad meteorological explanations, even their basic physics is wrong.
>> They blather on about "centrifugal force", which doesn't even exist!

>Well, except that unlike the whole lapse rate confusion, the idea of
>"centrifugal force" is perfectly valid, depending only on one's frame of
>reference, and complained about only by overly pedantic engineers and
>laymen.

And physics instructors while grading test answers.

Joe Morris

[Gary Drescher]

"Joe Morris" > wrote in message
...
> "Peter Duniho" > writes:
>
>>"jim rosinski" > wrote:
>>> [...]
>>> You're right about the ****-poor nature of FAA texts though. Not just
>>> the bad meteorological explanations, even their basic physics is wrong.
>>> They blather on about "centrifugal force", which doesn't even exist!
>
>>Well, except that unlike the whole lapse rate confusion, the idea of
>>"centrifugal force" is perfectly valid, depending only on one's frame of
>>reference, and complained about only by overly pedantic engineers and
>>laymen.
>
> And physics instructors while grading test answers.

I'd hope that physics instructors would realize that centrifugal force does
exist from the turning object's accelerated reference frame. It's just from
an inertial reference frame that centrifugal force is "fictitious". Either
reference frame is valid; you just have to be careful to specify which one
you're using.

Similarly, from the standpoint of curved spacetime, gravity is a
"fictitious" force. When you cruise near a planet, you just follow a
straight line (through curved spacetime), without being diverted by (or
feeling the influence of) any force. The pressure you feel on the seat of
your pants is analogous to centripetal force--it's the "real" force that
*opposes* the "fictitious" gravitational force.

Still, from our more familiar frame of reference, the force of gravity is
quite real, and we shouldn't object to the FAA's invocation of gravity, or
of centrifugal force.

--Gary

[Icebound]

"Andrew Sarangan" > wrote in message
1...
> 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.

As Jim pointed out, the moist (saturated) adiabatic rate is not constant,
but anything from about 1 to about 3 deg C per 1000. Because the amount of
condensing moisture is different at different dewpoints, and therefore the
amount of heat released is different in the different situations. If no
condensation is occurring, yes, then it is only 3/1000.

I have only recently sat through my first aviation ground school.
Meteorology was taught by a pilot, not a meteorologist. The pilot himself
had obvious lack of understanding of the subject. After his instruction, we
have 30 new potential pilots in a second generation with similar
misconceptions. Eventually one or more of them are going to become CFIs.
They may upgrade their meteorological education.... or NOT; the current
instructor didn't.

I have not checked this out in detail:

http://66.208.12.20/amsedu/online/info/

but it appears to be EXACTLY what pilots could use. The full one-time
course fee at $250 is a bargain in the context of your overall flying costs.
Even the no-license-fee "textbook-only" option would help us all.

By the way, the American Meteorological Society, in case you don't know, has
been around since 1919, and is THE organization for professional
meteorologists in the USA, so I am pretty confident that you will be getting
your money's worth.

[Icebound]

"jim rosinski" > wrote in message
oups.com...
>
....
> Not just
> the bad meteorological explanations, even their basic physics is wrong.
> They blather on about "centrifugal force", which doesn't even exist!
> What does exist is centripetal acceleration, which acts in the opposite
> direction of the mythical "centrifugal force".
>

Ooops, Jim. Just when you had them on your side :-) :-)

[Corky Scott]

On 7 Feb 2005 20:06:38 -0800, "jim rosinski" >
wrote:

>Agreed. I really am pleased to see this much interest, and frankly
>knowledge, displayed by pilots for a subject I've spent a good part of
>my life studying.
>
>Jim Rosinski

Jim, to me this is kind of the point regarding this subject and the
FAA's insistance on it being a part of the written examination. How
does knowing this information help the average pilot in his task of
flying safely from one point to another.

Does any pilot (besides yourself) actually think about this while
flying? If so when? Under what circumstances?

After a while don't pilots kind of get to understand when clouds begin
forming due to warming? And when the clouds do form, don't we (VHF
guys) normally just avoid them?

Thanks, Corky Scott

[Michael]

Andrew Sarangan wrote:
> 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.

There is an excellent explanation of all this stuff (including how to
predict cloud bases, the presence of vertical air currents, and the
likelihood of T-storms) in Reichmann's "Streckensegelflug" (man I hope
I got that right) which is translated into English (the whole book -
you need not speak German) as "Cross Country Soaring." It includes the
use of the Stuve diagram to predict what the atmosphere is going to do.

> I would bet you any money that if you took a survey of CFI's
> most would not know this fact.

Sure, as long as you limit to power-only CFI's. I can't think of any
glider CFI's who have not read Reichmann, though of course anything is
possible.

Michael

[Icebound]

"Corky Scott" > wrote in message
...
>
> Does any pilot (besides yourself) actually think about this while
> flying? If so when? Under what circumstances?
>
> After a while don't pilots kind of get to understand when clouds begin
> forming due to warming? And when the clouds do form, don't we (VHF
> guys) normally just avoid them?
>

Perhaps there are parts of the country where that is true, but in the
4-seasons part of the world....
yes, you should be thinking about these things BEFORE flying, not just WHILE
flying.

Now I DO agree that knowing the "fact" that the
dry-adiabatic-lapse-rate-is-3-degrees-Celsius-per-thousand-feet and being
able to check off the correct multiple-choice-box on the FAA or
Transport-Canada exam... is somewhat irrelevant if we do not take that fact
and understand it within the context of the rest of our weather environment.

And I have this belief that some of our instructors are concentrating on
ensuring we pass the exam by knowing these "facts", just as they did,
without really understanding nor properly communicating the broader subject
of aviation meteorology to us.
Therefore, it is left to US to obtain that understanding somehow. We should
not cancel our willingness, hell, our *obligation* to learn, once we walk
out of that ground-school session.


As has been often recorded in these newsgroups, TAFs are often "wrong".
Sometimes even METAR observations are less than perfect, especially from
AUTO sites.

If we had a real good understanding of all aspects of meteorology, we could
recognize the situations in which forecasting should be relatively "easy",
and the situation is which it is more "difficult".... therefore the
situation in which we can take the TAF as gospel, and the situation in which
it is likely to be suspect.

We would recognize not only the "actual" forecast for your area, but also
the "potential" of what the other possibilities were. This works both
ways.... we would recognize the potential for good weather when the TAF said
no, and we would recognize the potential for bad weather when the TAF said
go.

We would recognize whether the formation of an unexpected cloud bank is
potentially dangerous or benign. We would recognize whether an unexpected
clearing is real (and may be bad timing on the part of the TAF), or just a
sucker-hole.

We would understand the "thinking behind the TAF" and we would be in a
position to do our own "now-casting" if the
underlying-conditions-to-that-thinking have changed.... because we would
understand what "underlying conditions" to look for, and what their
implications are.

Knowing more about the underlying meteorology of your current situation will
not only help us avoid current BAD weather... it will help us understand
when GOOD-weather-going-bad is a possibility, and it will help us to
understand the difference between MARGINAL-weather-getting-good and
marginal-weather-getting-bad.

I have a real fear that the new generation of in-cockpit tools to
"upload-the-weather" will further deteriorate our desire to learn. If we
are going to use those tools only to "avoid the bright spots on the map",
then I am afraid that they will not increase our safety factor one bit.

I am certain (well okay: hopeful, anyway) that a very large segment of the
pilot population was well taught, understand meteorology very well and are
doing all they can to learn more and learn correctly. I do fear, however,
that some of us were not only poorly taught, but have accepted that as the
"norm" to be passed on to the next generation. And we now treat meteorology
as just one more check-mark on the exam to be forgotten-about, once passed.

(Pardon me for cross-posting to r.a.s, where this really belongs.)

[Darrell S]

Whoops. Typing error. the last entry should read "the average is 2°.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

"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°

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

"Andrew Sarangan" > wrote in message 1...
> Instability produces cumulus clouds and stability produces stratus clouds.
> We know that. However, since the saturated and unsaturated lapse rates are
> significantly different (1C/1000' compared to 3C/1000'), it seems quite
> possible to get cumulus clouds even when the atmosphere below is stable.
> For instance, if the environmental lapse rate is 2C/1000', the unsaturated
> air is stable. Once clouds form (how they form without vertical currents is
> a different matter), the air inside the clouds will become unstable. Does
> this seem reasonable?
>
> On a related question, where does the concept of 'average' lapse rate
> (2C/1000') come from? I always took this to mean 50% RH air, but it took me
> a long time to learn that that was not the case. The air is saturated or it
> is unsaturated. How can there be an average between saturated and
> unsaturated? The standard lapse rate and standard temperature at
> different elevations are all based on this 2C/1000' concept. What's the
> deal with this?
>
>

[jim rosinski]

Corky Scott wrote:

> Jim, to me this is kind of the point regarding this subject and the
> FAA's insistance on it being a part of the written examination. How
> does knowing this information help the average pilot in his task of
> flying safely from one point to another.

I agree the lapse rate stuff and implications for stability/instability
aren't of much practical value while flying. The main things are being
able to look at the sky and make some assessment of whether flying is a
good idea, and knowing what aspects of meteorological data might
warrant alarm. For example:

o Lenticulars over the mountains => won't be flying in the mountains
today (high winds).
o Smog over Denver => inversion, might be some bumps at the inversion
but no reason not to go flying.
o Temperature-dewpoint spread dropping toward zero => uh-oh, fog might
form. Don't stray too far.
o Low clouds forming east of the Rockies => upslope, bad weather moving
in. Maybe IMC soon.

Most pilots know these things, which I think are more important for
safe flying than some of the more esoteric aspects of atmospheric
science. And layman-level understanding of local meteorological warning
signs (I've given a few for the Denver area above) is really money in
the bank.

Jim Rosinski

[Icebound]

"Michael" > wrote in message
ups.com...
> Andrew Sarangan wrote:
....>
>>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.
....snipped...
>> I would bet you any money that if you took a survey of CFI's
>> most would not know this fact.
>
> Sure, as long as you limit to power-only CFI's. ...

I have no doubt that this is absolutely correct.

Not being a soarer, but I expect he/she not only knows the "conditions" that
give rise to good thermal lift, but also the meteorological situations to
look for which are conducive.

Power pilots as a group seem less interested in the meteorological
situation. Give them the ceiling and visibility numbers from the TAF and
METAR and they go on that. Nobody seems to ask WHY does the TAF lower the
ceiling after 2100Z... If the ceiling should lower two hours early at 1900Z
instead of 2100Z, many are totally lost and simply consider this a "bad
forecast".

[Michael]

> Power pilots as a group seem less interested in the meteorological
> situation. Give them the ceiling and visibility numbers from the TAF
and
> METAR and they go on that. Nobody seems to ask WHY does the TAF
lower the
> ceiling after 2100Z... If the ceiling should lower two hours early at
1900Z
> instead of 2100Z, many are totally lost and simply consider this a
"bad
> forecast".

I think it's less a matter of disinterest and more a matter of
ignorance. Knowledge of meteorology isn't something that can
effectively be tested using a government-issue multiple choice test,
and it's not particularly easy to test in an oral exam either. For
that matter, it's not easy to teach, and it sure isn't easy to learn
from a textbook. I would have to say that of all the important
aviation topics, meteorology is the most poorly taught and the most
poorly understood. Power pilots as a group are simply not qualified to
speculate WHY the TAF lowers the ceiling after 2100Z. Quite a few
don't even understand that they should be asking why.

One thing I've noticed is this - when an inexperienced pilot cancels a
trip based on a forecast, very rarely is it a matter of good judgment -
meaning the weather is likely to be beyond the pilot's capabilities for
the reasons he believes to be true. Usually it's a matter of poor
understanding - he cancels because he doesn't understand what the
weather is actually doing, and this state of ignorance (quite properly)
scares him. Even when the weather is beyond his capabilities, very
rarely is it for the reasons he thinks it is.

By the same token, the decision by an inexperienced pilot to make the
trip in something other than good weather forecast to stay that way is
rarely a matter of properly understanding that the weather, while not
really good, is within the pilot's capability - it's usually more a
matter of rolling the dice. Even when the weather is within his
capabilities, his logic for coming to that conclusion is generally very
flawed.

This isn't a good situation, but I have to say that in power flying
that's basically the way it is - and that goes double for instrument
flying. I find it amazing that anyone can believe he is making
intelligent decisions with regard to his safety margins against
encountering icing and T-storms in IMC in any but the most clearcut
cases without an understnading of what lapse rates mean, yet here we
have quite a few instrument pilots and instrument instructors still
hashing out the topic. And I'm going to be honest - had I not had my
glider rating long before my instrument rating, and my CFI-G long
before my CFII, I would likely have been just as ignorant.

While I admit it's possible in theory to learn enough about meteorology
from books and classes to make competent go/no-go decisions, I have to
say that I've never actually seen it happen in practice. In reality,
the only people I know who have actually learned to understand what the
weather is doing sufficiently to realistically asess the flight risks
are those who have flown in the weather. Unfortunately, every one of
these people has scared himself more than once by having misunderstood
or ignored some seemingly minor but actually very important factor.
And lest you think that it's somehow different for gliders, every one
of those glider pilots who has become pretty good at knowing what the
weather is doing has stories of guessing wrong and making an
off-airport landing or escaping one only by the skin of one's teeth.

Michael

[Icebound]

"Michael" > wrote in message
oups.com...
.... many relevant observations snipped....
>
> This isn't a good situation, but I have to say that in power flying
> that's basically the way it is - and that goes double for instrument
> flying.
....more relevant observations snipped....
> And lest you think that it's somehow different for gliders, every one
> of those glider pilots who has become pretty good at knowing what the
> weather is doing has stories of guessing wrong and making an
> off-airport landing or escaping one only by the skin of one's teeth.

I had been around the periphery of aviation for many years, but have only
had my very first peeks "inside" since mid-2004.

What you have said mirrors that meager experience perfectly. It surprised
me a little...maybe more than a little.

[Julian Scarfe]

"Andrew Sarangan" > wrote in message
1...
> Instability produces cumulus clouds and stability produces stratus clouds.
> We know that. However, since the saturated and unsaturated lapse rates are
> significantly different (1C/1000' compared to 3C/1000'), it seems quite
> possible to get cumulus clouds even when the atmosphere below is stable.
> For instance, if the environmental lapse rate is 2C/1000', the unsaturated
> air is stable. Once clouds form (how they form without vertical currents
is
> a different matter), the air inside the clouds will become unstable. Does
> this seem reasonable?

I think there's an aspect to this that hasn't been discussed. It *does*
require instability to produce cumulus cloud, but that instability can be
very local. So you may see an average environmental lapse rate of 2
degC/1000' through the lowest 3000' of the atmosphere, but actually you've
got at least patches of surface being heated by the sun, producing higher
temperatures and local instability. In that simple example, if you heat a
thin layer at the surface by just 3 degC, you've now got instability and the
makings of vertical convection.

That's not to say that stratiform clouds can't become unstable by the
mechanism you propose, but cu can form, particularly close to the surface,
in atmospheres that start off looking stable.

Julian Scarfe

[Corky Scott]

On Tue, 8 Feb 2005 12:25:34 -0500, "Icebound"
> wrote:

>If we had a real good understanding of all aspects of meteorology, we could
>recognize the situations in which forecasting should be relatively "easy",
>and the situation is which it is more "difficult".... therefore the
>situation in which we can take the TAF as gospel, and the situation in which
>it is likely to be suspect.

Can you give me a realistic example of how knowing exactly what the
definition of lapse rate is would help a pilot flying from point A to
point B?

Forgive me, I'm just trying to understand why the FAA considers this
so important that it is put on the written. I've never heard of
anyone calculating the lapse rate for a flight. Even if they did, it
seems to me that this rate could easily be different from one point to
the next throughout the flight.

I understand the need to be thorough when flight planning but I don't
get how to use this particular knowledge.

Thanks, Corky Scott

[private]

Nicely done guys. This thread is the Usenet we all enjoy.

A Chinook is the classic demonstration of lapse rate in action. You can
even see it on the satellite feeds.

From a pilots perspective there are only three kinds of weather.
Getting better
Getting worse
Staying the same
All of our studying and experience are drawn on to make this judgment, and I
think it is true to say that you can't have too much weather knowledge.
Ultimately weather and running out of fuel seem to be the biggest cause of
aviation fatalities.

The internet is a wonderful resource for students of life as there is a huge
amount of very good material available for free and the access to aviation
weather maps and data lets us practice our skills by constantly watching the
sky and asking yourself, if you were flying today
is it getting better or worse?
and where is the hidden weather killer hiding?

I make it a point to check the aviation weather daily and find that my
forecasts are usually as good as the very good TV weather (CFCN) I also
find this practice useful for forecasting powder snow and use my knowledge
of lapse rates and winds aloft to estimate whether it is likely to be heavy
or light and its effect on the avalanche hazard or if the high chairlift
will be closed for wind..

Weather newsgroup sci.gen.meteorology Most of the guys on
this group know way more than me, but then that's true here too.

The following is a repost, my appologies to the usenet purists.

When the local FSS were closed NavCan recognized that the briefers in the
centers may lack the local knowledge that the local FSS had provided. A
project to gather this local knowledge for briefer training lead to the
production of weather manuals for each of the weather regions. These
manuals are available on their website. The general weather chapter seems
to be common to each manual and is as good as any of the pilot weather books
I have read, with the possible exception of the TC Air Command Weather
Manual CFACM 2-700 ( TC. TP9352E)

http://www.navcanada.ca/NavCanada.aspLanguage=en&Content=ContentDefinitionFi
les\Publications\LAK\default.xml

My favorite weather source is

http://www.flightplanning.navcanada.ca/cgi-bin/CreePage.pl?Langue=anglais&No
Session=NS_Inconnu&Page=rb&TypeDoc=html

Blue skies to all





"Icebound" > wrote in message
...
>
> "Michael" > wrote in message
> oups.com...
> ... many relevant observations snipped....
> >
> > This isn't a good situation, but I have to say that in power flying
> > that's basically the way it is - and that goes double for instrument
> > flying.
> ...more relevant observations snipped....
> > And lest you think that it's somehow different for gliders, every one
> > of those glider pilots who has become pretty good at knowing what the
> > weather is doing has stories of guessing wrong and making an
> > off-airport landing or escaping one only by the skin of one's teeth.
>
> I had been around the periphery of aviation for many years, but have only
> had my very first peeks "inside" since mid-2004.
>
> What you have said mirrors that meager experience perfectly. It surprised
> me a little...maybe more than a little.
>
>
>
and many previous posters

[Icebound]

"Corky Scott" > wrote in message
...
> On Tue, 8 Feb 2005 12:25:34 -0500, "Icebound"
> > wrote:
>
>>If we had a real good understanding of all aspects of meteorology, we
>>could
>>recognize the situations in which forecasting should be relatively "easy",
>>and the situation is which it is more "difficult".... therefore the
>>situation in which we can take the TAF as gospel, and the situation in
>>which
>>it is likely to be suspect.
>
> Can you give me a realistic example of how knowing exactly what the
> definition of lapse rate is would help a pilot flying from point A to
> point B?
>
....


If a pilot does not know the definition of lapse rate, then it is pretty
difficult for him to recognize the conditions which lead to atmospheric
buoyancy or to atmospheric stability.

I get to the airport on a clear summer morning. 7 AM. Sun is up. Not a
cloud in the sky. Temperature is 20C, dewpoint is 15. TAF for my airport
for later is PROB30 TSRA. TAF For airport 40 mi south for a similar time
period is TEMPO TSRA. Okay, only a risk of thunderstorms for me, more
definite for the guy down south.

As a pilot, I am interest in the possibilities of the TAF being "wrong". I
take off, fly up through the early-morning inversion and find the
temperature starts to fall off at about 4000 feet, peaking there at, say,
about 20 to 22 C.

*If I know* (maybe get a PIREP) that the 10,000 foot temperature in my area
is rather warm, say 14-15... that's maybe 1.5 degrees per 1000, pretty
stable in that mid layer and I'm pretty confident that even with good summer
heating only a few are likely to pop and I pretty much trust the TAF. I
know that it is "pretty stable" because I understand the concept of
adiabatic lapse rates and therefore know more-or-less how much colder a
rising air parcel will be than its environment.... and hence not buoyant.

But if I find out that the 10,000 foot temperature is closer to, say 6 or 8,
that's becoming 2.5 per 1000, and I am starting to consider the possibility
that my airmass maybe just as unstable as the guy down south and
Thunderstorms are a distinct possibility and something more than a "risk".

Am I likely to do exactly that kind of calculation in flight?

Maybe, maybe not..... If I did, would it affect my go-nogo decision? Maybe,
maybe not. But if I *did* go, I know what I would be looking out for, and I
would treat the first appearance of a Towering Cumulus quite differently in
those two situations. In the first case, I'm not panicking until I see a
few more.... in the second, I'm thinking seriously about heading for an
airport.

My rant was about knowledge of meteorological concepts in general, not lapse
rates in particular. Lapse rates were an easy target example because of the
obvious misunderstanding of adiabatic lapse rates in that particular post.
I agree that in a great many cases, knowing the actual lapse rate may not
help you much. You might not have the information, or it may be a situation
where it is not important. (And FAA or TC exams that test "knowledge" are a
whole other issue :-) )

But knowing the complete concept... how adiabatic lapse rates affect the
temperature of rising parcels... how that relates to the difference in
temperature between the environment and a rising air bubble... how that
difference in temperature affects buoyancy... how the degree of buoyancy
affects convection....

Knowledge of these concepts may just help you to understand the TAF, your
own observations, and how to reconcile a busted forecast.

[Corky Scott]

On Wed, 9 Feb 2005 18:29:52 -0500, "Icebound"
> wrote:

>If a pilot does not know the definition of lapse rate, then it is pretty
>difficult for him to recognize the conditions which lead to atmospheric
>buoyancy or to atmospheric stability.

You really think so? You feel that people would not/do not understand
how and when clouds might form if they do not have an understanding of
what lapse rate is?

When I flew out to Oshkosh in '95 in the front seat of a Waco UPF-7,
we encountered a LOT of thunderstorms along our route. The plan was
to fly from Vermont due west staying south of the Great Lakes until we
reached Chicago, then turn right. Known as the "Northeast Corridor"
it's home to a lot of thunderstorm activity during the summer.
Typically, we'd fly along our route for as long as possible, and when
the sky filled with thunderstorms that we could no longer fly around,
we landed and waited them out. We ended up waiting more than we'd
planned due to the amount of storms we encountered. By the time we
turned north past Chicago, the storms were individually extremely
violent but isolated and we could and did just detour around them.

How would the pilot who truly understood lapse rate have flown it any
differently?

Thanks, Corky Scott

[Icebound]

"Corky Scott" > wrote in message
...
> On Wed, 9 Feb 2005 18:29:52 -0500, "Icebound"
> > wrote:
>
>>If a pilot does not know the definition of lapse rate, then it is pretty
>>difficult for him to recognize the conditions which lead to atmospheric
>>buoyancy or to atmospheric stability.
>
> You really think so? You feel that people would not/do not understand
> how and when clouds might form if they do not have an understanding of
> what lapse rate is?

Well, no, pretty much by definition they would not.

Many sunny days clouds form. Many other sunny days they do not. Should we
just be *surprised* by the formation of cloud on this day, or *surprised* by
the absence of cloud on another?

If you know that on sunny days clouds form because bubbles of air move
upward and cool to the point of condensation, you already know something
about environmental and adiabatic lapse rates, even if you will not admit
it. Otherwise, why would you expect clouds to form even if these bubbles do
float upward?


> When I flew out to Oshkosh in '95 in the front seat of a Waco UPF-7,
> we encountered a LOT of thunderstorms along our route. The plan was
> to fly from Vermont due west staying south of the Great Lakes until we
> reached Chicago, then turn right. Known as the "Northeast Corridor"
> it's home to a lot of thunderstorm activity during the summer.
> Typically, we'd fly along our route for as long as possible, and when
> the sky filled with thunderstorms that we could no longer fly around,
> we landed and waited them out. We ended up waiting more than we'd
> planned due to the amount of storms we encountered. By the time we
> turned north past Chicago, the storms were individually extremely
> violent but isolated and we could and did just detour around them.
>
> How would the pilot who truly understood lapse rate have flown it any
> differently?
>

You asked for a practical situation and I gave you one.

Maybe he would fly your situation no differently at all... As I said before,
lots of situations when the pilot will not have sufficient information
beyond what he sees out the window.

But he *would* be flying with the subtle difference that he is pressing on
because he understands what is happening here and can *anticipate any
changes*, rather than just *react to changes*. And he would also be more
comfortable *in advance* about the probability of his
success-without-diversion.

[Corky Scott]

On Thu, 10 Feb 2005 14:19:44 -0500, "Icebound"
> wrote:

>Maybe he would fly your situation no differently at all... As I said before,
>lots of situations when the pilot will not have sufficient information
>beyond what he sees out the window.
>
>But he *would* be flying with the subtle difference that he is pressing on
>because he understands what is happening here and can *anticipate any
>changes*, rather than just *react to changes*. And he would also be more
>comfortable *in advance* about the probability of his
>success-without-diversion.

Ok, my apologies once again for seeming so dense about this.

I had another bunch of scenario's all worked up for argument's sake,
but have decided to just let this go.

Thanks for your information

Corky Scott

[Rob]

Corky,

With knowledge of the surface temperature, dewpoint, and lapse rate a
pilot can make an educated guess at what altitude cloud bases are
likely to be. Also, with knowledge of the temperature at your altitude
and lapse rate you can estimate your proximity to the freezing level.
Granted, lapse rates vary greatly and these "calculations" are more
like ballpark guesses, but they're still valuable.

Regards,

Rob

[Dana M. Hague]

On Tue, 08 Feb 2005 10:01:35 -0500, Corky Scott
> wrote:

>Jim, to me this is kind of the point regarding this subject and the
>FAA's insistance on it being a part of the written examination. How
>does knowing this information help the average pilot in his task of
>flying safely from one point to another.
>
>Does any pilot (besides yourself) actually think about this while
>flying? If so when? Under what circumstances?

GA pilots might not use it much. For glider pilots it can be very
valuable, as a predictor of when and where thermals will form. Also
ultralights, since it's also a good predictor of how smooth the air
will be (thermic days can be uncomfortable if not downright dangerous
in the extreme low end of ultralights like powered paragliders).

-Dana
--
--
If replying by email, please make the obvious changes.
-------------------------------------------------------------------------------Daddy, why doesn't this magnet pick up this floppy disk?

[Icebound]

"Corky Scott" > wrote in message
...
> On Thu, 10 Feb 2005 14:19:44 -0500, "Icebound"
....
> Ok, my apologies once again for seeming so dense about this.
>
.....

No need.

My instructors did not really have to tell me all the gory details about how
that big red knob next to the throttle works. All they really had to say
was "when you get above about 3000 feet, you'll get a little more power if
you pull it out a bit... but not too far or the RPM will drop... and on your
way down push it in a bit... and stick it right to the dash when landing or
taking off..." That would have probably been enough to get me by.

But knowing the relationships between air/gas mixtures and fuel consumption
and engine cooling and engine power, etc., helps me use that little knob a
little smarter.

I think you can look at knowing the underlying weather theory the same
way... it helps you use TAFs, area forecasts, radar imaging, and even your
own observations... just a little bit smarter.

All the best.

[Andrew Sarangan]

Lapse rate can also tell you what type of icing you are likely to get.
Unstable clouds are more likely to have clear ice (the bad kind), and
stable clouds are likely to be rime ice.



"Icebound" > wrote in
:

>
> "Corky Scott" > wrote in message
> ...
>> On Wed, 9 Feb 2005 18:29:52 -0500, "Icebound"
>> > wrote:
>>
>>>If a pilot does not know the definition of lapse rate, then it is
>>>pretty difficult for him to recognize the conditions which lead to
>>>atmospheric buoyancy or to atmospheric stability.
>>
>> You really think so? You feel that people would not/do not
>> understand how and when clouds might form if they do not have an
>> understanding of what lapse rate is?
>
> Well, no, pretty much by definition they would not.
>
> Many sunny days clouds form. Many other sunny days they do not.
> Should we just be *surprised* by the formation of cloud on this day,
> or *surprised* by the absence of cloud on another?
>
> If you know that on sunny days clouds form because bubbles of air move
> upward and cool to the point of condensation, you already know
> something about environmental and adiabatic lapse rates, even if you
> will not admit it. Otherwise, why would you expect clouds to form
> even if these bubbles do float upward?
>
>
>> When I flew out to Oshkosh in '95 in the front seat of a Waco UPF-7,
>> we encountered a LOT of thunderstorms along our route. The plan was
>> to fly from Vermont due west staying south of the Great Lakes until
>> we reached Chicago, then turn right. Known as the "Northeast
>> Corridor" it's home to a lot of thunderstorm activity during the
>> summer. Typically, we'd fly along our route for as long as possible,
>> and when the sky filled with thunderstorms that we could no longer
>> fly around, we landed and waited them out. We ended up waiting more
>> than we'd planned due to the amount of storms we encountered. By the
>> time we turned north past Chicago, the storms were individually
>> extremely violent but isolated and we could and did just detour
>> around them.
>>
>> How would the pilot who truly understood lapse rate have flown it any
>> differently?
>>
>
> You asked for a practical situation and I gave you one.
>
> Maybe he would fly your situation no differently at all... As I said
> before, lots of situations when the pilot will not have sufficient
> information beyond what he sees out the window.
>
> But he *would* be flying with the subtle difference that he is
> pressing on because he understands what is happening here and can
> *anticipate any changes*, rather than just *react to changes*. And
> he would also be more comfortable *in advance* about the probability
> of his success-without-diversion.
>
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