Jet aircraft pollution (NASA)
Claire Gilbert
NASA Headquarters
Every day, thousands of jet aircraft fly through the Earth's
atmosphere, but scientists are still uncertain how much pollution
is produced. To better understand this relatively unknown source
of air pollution, researchers at NASA's Langley Research Center,
Hampton, Virginia, are measuring emissions from the engines of two
NASA research jets - a Boeing 737 and a Boeing 757.
During a two-week experiment, as part of NASA's Atmospheric
Effects of Aviation Project (AEAP), a NASA T-39 jet will fly behind
a NASA 737. Instruments aboard the T-39 will measure various
chemicals and small pollutant particles (called aerosols) emitted
by the 737's engines. The T-39 data also will be used to study how
the 737's engine emissions disperse in the atmosphere, and how
rapidly. Jet engine emissions can often be seen in the atmosphere
in the form of contrails flowing behind the aircraft.
The NASA 737 also will fly over a ground-based laser system at
Langley that can measure how many aerosols are emitted from the en-
gines. These aerosol measurements can be used as tracers to study
how air flows around the jet, dispersing the emissions into the
atmosphere. Jet engine emissions have been shown to affect the
concentrations of atmospheric water vapor and aerosols, and they
may affect how clouds form and the concentrations of atmospheric
ozone. Few actual measurements of their effects have been made,
however.
In addition to the ground-based laser system and the T-39,
researchers from the University of Missouri-Rolla will measure
engine emissions from both the 737 and the 757 in ground tests at
Langley. Using a probe mounted near the rear of the engine, the
University of Maryland (sic) researchers will measure how many
aerosols are emitted by each engine and their relative sizes.
The data collected during this experiment will provide AEAP
scientists with a unique data set to help them better understand
how jet aircraft emissions are affecting our atmosphere and how
these emissions are dispersed.
================================================================
* From Blazing Tattles, 2/96 VALENTINE SEX ISSUE. All
copyright laws apply. Issue contains the following articles:
EDITORIAL: What has sex to do with Blazing Tattles? LETTERS: Is
the globe heating up?, Do French have Gulf War Syndrome? Thank you
DuPont, Mellon & Hearst. HEALTH: Getting good touch and caring
intimacy, ~Book Review~ by Dennis Fink, M.S., THE CURE FOR ALL
DISEASES, Cholesterol & amalgam, Ebola, Ear problems & aspartame,
Breast cancer & nutrition. EYES OF THE MOTHER: An atomic fable,
Isaac's apple, by David Yarrow. PETROLEUM: Secret air board
agreement will suppress electric cars. WEATHER: Jet aircraft, How
large a source of atmospheric pollution? NASA Headquarters.
ECOSYSTEMS: 1977 -- Year of the Reef. SUSTAINABILITY: DEVELOPING
IDEAS, EARTHSCORE. GULF WAR AFTERMATH: Gulf War Illness is NO
mystery! by Claire W. Gilbert. CONSUMER INFORMATION: Dioxin
activists make a difference, Health care disgrace, Clean Energy
Technologies confirms new source. MEDIA: More greenwashing --
oops! Coors. H.E.I.R.S. Clips.
COMPLIMENTARY NEWEST ISSUE: Send SASE to: Blazing Tattles,
P.O. Box 1073, Half Moon Bay, CA 94019.
Jim Scanlon
the below article
For a very detailed examination of the atmospheric effects of aircraft
please refer to the Journal of Geophysical Research. Unfortunately I
cannot locate the issue. I believe it was published in 1994 by a German
researcher. I remember a detailed discussion of the height of the
tropopause and thinking how this is something usually taken as static,
whereas it isn't.
Jim Scanlon
--
199 Canal St #8
San Rafael CA
94901
415-485-0540
Carl J Lydick
=rapidly. Jet engine emissions can often be seen in the atmosphere
=in the form of contrails flowing behind the aircraft.
Claire, can't you EVER take the time and trouble to get your facts straight
before you distort them? A contrail (short for condensation trail) results
when an object travelling through air supersaturated with water vapor causes
that water vapor to condense. When you see a contrail, you're seeing, at best,
an indirect result of the emissions of the jet (particulates provide nucleation
sites which permits condensation); at worst, what you're seeing has nothing to
do with emissions from the aircraft (turbulence can cause contrails).
--------------------------------------------------------------------------------
Carl J Lydick | INTERnet: CA...@SOL1.GPS.CALTECH.EDU | NSI/HEPnet: SOL1::CARL
Disclaimer: Hey, I understand VAXen and VMS. That's what I get paid for. My
understanding of astronomy is purely at the amateur level (or below). So
unless what I'm saying is directly related to VAX/VMS, don't hold me or my
organization responsible for it. If it IS related to VAX/VMS, you can try to
hold me responsible for it, but my organization had nothing to do with it.
DaveHatunen
[...]
> Jet engine emissions can often be seen in the atmosphere
>in the form of contrails flowing behind the aircraft.
Um. You need to get your facts right. Contrails are not from jet
engines. B-29s used to create contrails.
In fact, they are not from engines at all. They are mostly a wingtip
phenomenon, caused by the the altered air physics at the wingtips,
where vortices are formed.
--
********** DAVE HATUNEN (hat...@netcom.com) **********
* Daly City California *
* Between San Francisco and South San Francisco *
*******************************************************
Claire Gilbert
DaveHatunen <hat...@netcom.com> wrote:
>
>[...]
>
>> Jet engine emissions can often be seen in the atmosphere
>>in the form of contrails flowing behind the aircraft.
>
>Um. You need to get your facts right. Contrails are not from jet
>engines. B-29s used to create contrails.
>
>In fact, they are not from engines at all. They are mostly a wingtip
>phenomenon, caused by the the altered air physics at the wingtips,
>where vortices are formed.
Your opinion is very interesting. I quoted directly from what NASA
has to say about the subject. NASA needs to get its facts straight,
according to you.
Claire Gilbert
Scott Nudds
: Your opinion is very interesting. I quoted directly from what NASA
: has to say about the subject. NASA needs to get its facts straight,
: according to you.
Don't worry Claire, professional denialists will say or do anything to
defend their cornacopian dogma.
--
Rob Haydt Suzanne Hartley
>Um. You need to get your facts right. Contrails are not from jet
>engines. B-29s used to create contrails.
>
>In fact, they are not from engines at all. They are mostly a wingtip
>phenomenon, caused by the the altered air physics at the wingtips,
>where vortices are formed.
>
So how is that aircraft with 4 engines (e.g. B747) have a contrail with
4 sections? On a very clear day, you can easily distinguish a 4-engine
jet from a 2-engine jet.
DaveHatunen
>In article <hatunenD...@netcom.com>,
>DaveHatunen <hat...@netcom.com> wrote:
>>
>>[...]
>>
>>> Jet engine emissions can often be seen in the atmosphere
>>>in the form of contrails flowing behind the aircraft.
>>
>>engines. B-29s used to create contrails.
>>
>>In fact, they are not from engines at all. They are mostly a wingtip
>>phenomenon, caused by the the altered air physics at the wingtips,
>>where vortices are formed.
>
>has to say about the subject. NASA needs to get its facts straight,
>according to you.
I just backed up in the thread and looked at your post again. I see no
attribution showing that the words quoted are from NASA. It looks more
like a news article datelined "NASA Headquarters" (whatever that is).
Perhaps you could clarify for us just what the source of the article
was.
DaveHatunen
>In article <hatunenD...@netcom.com>,
>DaveHatunen <hat...@netcom.com> wrote:
>>
>>[...]
>>
>>> Jet engine emissions can often be seen in the atmosphere
>>>in the form of contrails flowing behind the aircraft.
>>
>>Um. You need to get your facts right. Contrails are not from jet
>>engines. B-29s used to create contrails.
>>
>>In fact, they are not from engines at all. They are mostly a wingtip
>>phenomenon, caused by the the altered air physics at the wingtips,
>>where vortices are formed.
>
>Your opinion is very interesting. I quoted directly from what NASA
>has to say about the subject. NASA needs to get its facts straight,
>according to you.
If NASA's postion is that contrails are caused by jet engine
pollutants, it does indeed need to get its facts straight. Perhaps some
PR flack got his facts mixed up...
Claire Gilbert
DaveHatunen <hat...@netcom.com> wrote:
>>
>>Your opinion is very interesting. I quoted directly from what NASA
>>has to say about the subject. NASA needs to get its facts straight,
>>according to you.
>
>attribution showing that the words quoted are from NASA. It looks more
>like a news article datelined "NASA Headquarters" (whatever that is).
>
>Perhaps you could clarify for us just what the source of the article
>was.
>
>
It is very common to print press releases without attributions. Journalists
do that all the time. I do it when the source is generally trustworthy.
In my judgement, I thought the information was of interest to those
interested in climate change, etc.
Claire Gilbert
Scott Lindstrom
|> In article <4jr294$o...@crl10.crl.com>, Claire Gilbert <bla...@crl.com> wrote:
|> >>
|> >>> Jet engine emissions can often be seen in the atmosphere
|> >>>in the form of contrails flowing behind the aircraft.
|> >>
|> >>Um. You need to get your facts right. Contrails are not from jet
|> >>engines. B-29s used to create contrails.
|> >>
|> >>In fact, they are not from engines at all. They are mostly a wingtip
|> >>phenomenon, caused by the the altered air physics at the wingtips,
|> >>where vortices are formed.
|> >
|> >has to say about the subject. NASA needs to get its facts straight,
|> >according to you.
|>
|> pollutants, it does indeed need to get its facts straight. Perhaps some
|> PR flack got his facts mixed up...
|>
Or, perhaps your information is not complete. I refer you to the ol' standby
Glossary of Meteorology, which allows for two different formation mechanisms for
condensation trails ("a cloud-like streamer frequently observed to form behind
aircraft flying in clear, cold, humid air"). One is apparently what NASA and by
quoting them Claire is describing, i.e., exhaust trails; you seem to be
describing aerodynamic trails, a rather more scarce occurrence.
Scott
--
Scott S. Lindstrom | The only other sound's
sco...@ssec.wisc.edu | the sweep of easy
http://www.ssec.wisc.edu/~scottl/homepage1.html | wind and downy flake
Eric P. Salathe, Jr.
> Jet engine emissions can often be seen in the atmosphere
> in the form of contrails flowing behind the aircraft.
It was objected that these are not polution, but a thermodynamic effect.
Claire goes on to say:
> I quoted directly from what NASA
> has to say about the subject. NASA needs to get its facts straight,
> according to you.
> In my judgement, I thought the information was of interest to those
> interested in climate change, etc.
Agreed. Whether the contrails from the jet engines are primarily due to a
thermal or aerosol souce (both are present) is immaterial. The contrails
themselves are an environmental perturbation due to a the aircraft, hence, by
definition, pollution (which is not restricted to burger cartons on the
roadside). These contrails potentially lead to a considerable increase in
cirrus cloudiness, which can impact the atmospheric radiation balance.
--
,
Eric P. Salathe, Jr. sal...@atmos.washington.edu
Seattle, Washington http://atmos.washington.edu/~salathe
Tom Woolner
>In article <hatunenD...@netcom.com>,
>DaveHatunen <hat...@netcom.com> wrote:
>
>>In fact, they are not from engines at all. They are mostly a wingtip
>>phenomenon, caused by the the altered air physics at the wingtips,
>>where vortices are formed.
>
>has to say about the subject. NASA needs to get its facts straight,
>according to you.
>
>
Contrails are clearly visible as issuing directly from wing-mounted
engines on high flying aircraft, or the engine cluster - not the
wingtips - of aircraft with tail mounted engines. This is easily
observed just by looking. Wing-tip vortices are sometimes observable
but at low altitudes and at high wing stress situations where the air is
spilling off the wing-tip. I have observed these at air-shows, for
example, where small heavy aircraft do impressive manoeuvres at close
range. These vortices disipate quite quickly - 5 to 15 seconds - after
formation.
I once observed NEGATIVE contrails from a low-level aircraft, just taken
off from a nearby airfield. The conditions were hot, humid with a low
layer of haze. As the plane passed through this haze, it left four
channels of clear air.
Regards,
Tom Woolner
Dave Halliwell
ha...@midget.iii.net (Rob Haydt Suzanne Hartley) writes:
>In article <hatunenD...@netcom.com>, hat...@netcom.com (DaveHatunen) says:
>>Um. You need to get your facts right. Contrails are not from jet
>>engines. B-29s used to create contrails.
>>In fact, they are not from engines at all. They are mostly a wingtip
>>phenomenon, caused by the the altered air physics at the wingtips,
>>where vortices are formed.
>So how is that aircraft with 4 engines (e.g. B747) have a contrail with
>4 sections? On a very clear day, you can easily distinguish a 4-engine
>jet from a 2-engine jet.
One of the byproducts of combustion is water vapour. Piston-slammers,
turbo-props, or jets all produce "more power" (apologies to Tim Taylor)
when they are burning fuel (as opposed to when they are not).
Engines generally don't bother storing all the water vapour they
produce when they burn fuel, so it is released to the atmosphere. If the
atmosphere is cold enough (which it is a lot of the time), the exhaust
gas will be supersaturated, and the vapour will condense to form a
contrail (a la Carl's explanation). The contrail marks the plume of
exhaust gases.
Claire's original post referred to "emissions". Obviously, the
exhaust gases _are_ "emitted" from the engine, but that doesn't mean that
contrails are pollution. Just calling something "emissions" doesn't
automagically mean that it is pollution, either.
Wings and wing-tip vortices can also cause condenstion in air close to
saturation, due to cooling caused by pressure changes. A good time to
observe this is when descending, just after coming down out of clouds on
a landing approach. Sometimes you'll see just the wind-tip vortices;
other times the whole top of the wing might be clouded over. Such
condensation plumes won't extend much beyond the airplane though: they
dissipate very quickly (unlike contrails from exhaust gases, which can
persist easily for several minutes).
--
Dave Halliwell I don't speak for my employers, and you
Edmonton, Alberta shouldn't expect them to speak for me.
Wayne Upham
>In article <4jeosp$l...@crl3.crl.com>, Claire Gilbert <bla...@crl.com> wrote:
>
>[...]
>
>> Jet engine emissions can often be seen in the atmosphere
>>in the form of contrails flowing behind the aircraft.
Some jet (or otherwise) engines have very smoky exhaust (like a B-52)
but I'm not sure you could call that a "contrail" (condensation trail)
>
>Um. You need to get your facts right. Contrails are not from jet
>engines. B-29s used to create contrails.
The exhaust from an engine jet or reciprocating is a oxygen and
hydrocarbon reaction and H2O and CO2 (and a small amount of nasties
from incomplete burning) are the result. The H2O from the hot exhaust
is rapidly cooled and will condense (provided the humidity is high
enough). The contrail will exist until moisture can evaporate; in some
conditions this can take an hour or more. There is an Air Force index
for predicting it.
>
>In fact, they are not from engines at all. They are mostly a wingtip
>phenomenon, caused by the the altered air physics at the wingtips,
>where vortices are formed.
This is an adiabatic cooling (from the sudden drop in air pressure due
to the Bernoulli effect of the wings). The sudden cooling causes the
moisture in the air to condense (provided the temperature drops to the
dew point). This effect is a common sight for a high performance jet
(fighter aircraft) making a high g maneuver. This effect is short
lived because the air pressure quickly returns to normal after the
aircraft has passed.
Wayne Upham
Meteorology student
U Mass Lowell
DaveHatunen
Scott Lindstrom <sco...@ssec.wisc.edu> wrote:
[...]
>Or, perhaps your information is not complete. I refer you to the ol' standby
>Glossary of Meteorology, which allows for two different formation mechanisms for
>condensation trails ("a cloud-like streamer frequently observed to form behind
>aircraft flying in clear, cold, humid air"). One is apparently what NASA and by
>quoting them Claire is describing, i.e., exhaust trails; you seem to be
>describing aerodynamic trails, a rather more scarce occurrence.
I have never seen an aerial photo of such "exhaust trails". But the
photos of WW2 B29s are almost classic in this regard.
I do wonder, though, that if the condensation of water vapor is what
is meant by "exhaust emissions" in a context referring to pollutants.
afre...@epix.net
From Dave Hatunen's message....
>
> Um. You need to get your facts right. Contrails are not from jet
> engines. B-29s used to create contrails.
If memory serves, the B29 was not a glider...it burned fuel, which
produced H2O, etc., etc.
> In fact, they are not from engines at all. They are mostly a wingtip
> phenomenon, caused by the the altered air physics at the wingtips,
> where vortices are formed.
You have very strange planes in CA (some with 3 wings?); here in the east
the contrails come right out of the engines. Or maybe we have the
strange planes. Whatever...
Eric Stevens
wrote:
>In article <4jeosp$l...@crl3.crl.com>, Claire Gilbert <bla...@crl.com> wrote:
>
>[...]
>
>> Jet engine emissions can often be seen in the atmosphere
>>in the form of contrails flowing behind the aircraft.
>
>Um. You need to get your facts right. Contrails are not from jet
>engines. B-29s used to create contrails.
>
>In fact, they are not from engines at all. They are mostly a wingtip
>phenomenon, caused by the the altered air physics at the wingtips,
>where vortices are formed.
>
Um. You need to get your facts right. :-)
B-29s used to create contrails from their engines and so do modern
aircraft, but not so easily. Water is a product of combustion an at
high altitudes the low temperatures will cause con-trails to form very
quickly. See the WW2 movies.
Contrails caused by the wingtip phenomenon you mentioned are caused by
the the altered air physics at the wingtips but because they lack
added water they are short lived.
where vortices are formed.
>
Eric Stevens
Chaos is found in the greatest abundance wherever order is being
sought. It always defeats order, because it is better organised.
-: Ly Tin Wheedle
Eric Stevens
>In article <hatunenD...@netcom.com>,
>DaveHatunen <hat...@netcom.com> wrote:
>>
>>[...]
>>
>>> Jet engine emissions can often be seen in the atmosphere
>>>in the form of contrails flowing behind the aircraft.
>>
>>Um. You need to get your facts right. Contrails are not from jet
>>engines. B-29s used to create contrails.
>>
>>In fact, they are not from engines at all. They are mostly a wingtip
>>phenomenon, caused by the the altered air physics at the wingtips,
>>where vortices are formed.
>
>Your opinion is very interesting. I quoted directly from what NASA
>has to say about the subject. NASA needs to get its facts straight,
>according to you.
You have not actually quoted the NASA text so I can't comment on it,
but:
I have flown at high altitudes in piston engined aircraft (Mosquitos
at +25,000ft) and watched the engine exhausts form contrails to the
horizon. Nothing from the wing tips.
I have looked at many photographs and movies of high altitude bomber
flights in WW2 and it is quite clear that they form four contrails per
aircraft, quite obviously from the four engines. If you count you will
see that they have but two wing tips. :-)
I have seen contrails formed by aircraft pulling high g manouveres in
humid air. The wing tip vortices may then form small contrails which
are only a few hundred meters long and last only a second or so.
To form a lasting contrail you need a concentration of more water than
normally is tin he atmosphere at that point. Piston engines produce a
water-rich exhaust which forms a lovely rich contrail. Gas turbines
and jets produce just as much water but it is diluted by as much as 5
times in comparison to a piston engine. On the other hand, a jumbo
burns a lot of fuel, much more than any piston engine and it too can
form a lovely contrail. The temperature and humidity has to be right
in any case. Wing tip vortices may form contrails at high altitudes,
but I would be surprised if anyone could see them - there is so little
water vapour in those regions.
Claire Gilbert
Eric Stevens <stev...@iprolink.co.nz> wrote:
>On 2 Apr 1996 03:15:48 -0800, bla...@crl.com (Claire Gilbert) wrote:
>
>>
>>Your opinion is very interesting. I quoted directly from what NASA
>>has to say about the subject. NASA needs to get its facts straight,
>>according to you.
>
>You have not actually quoted the NASA text so I can't comment on it,
>but:
>
>Eric Stevens
>
I was imprecise in my statement. I wasn't "quoting" NASA. I
posted a press release from NASA. I am reposting it below.
-----------------------------------------------------------
Jet aircraft: How large a source of atmospheric pollution?*
NASA Headquarters
Every day, thousands of jet aircraft fly through the Earth's
atmosphere, but scientists are still uncertain how much pollution
is produced. To better understand this relatively unknown source
of air pollution, researchers at NASA's Langley Research Center,
Hampton, Virginia, are measuring emissions from the engines of two
NASA research jets - a Boeing 737 and a Boeing 757.
During a two-week experiment, as part of NASA's Atmospheric
Effects of Aviation Project (AEAP), a NASA T-39 jet will fly behind
a NASA 737. Instruments aboard the T-39 will measure various
chemicals and small pollutant particles (called aerosols) emitted
by the 737's engines. The T-39 data also will be used to study how
the 737's engine emissions disperse in the atmosphere, and how
rapidly. Jet engine emissions can often be seen in the atmosphere
in the form of contrails flowing behind the aircraft.
afre...@epix.net
From Dave Hatunen:
> I just backed up in the thread and looked at your post again. I see no
> attribution showing that the words quoted are from NASA. It looks more
> like a news article datelined "NASA Headquarters" (whatever that is).
>
> Perhaps you could clarify for us just what the source of the article
> was.
>
This is not actually "my" thread...I'd asked for similar info and
couldn't resist tossing in a comment on NASA (contrails) thread.
Had run across the NASA release myself a while back - and did post the
reference here a couple days ago. However, it's possible it never got
there; news does get scrambled sometimes.
spacelink.msfc.nasa.gov:80/
NASA.Projects/Aeronautics/Aeronautics.News.Releases/
96-02-16.Jets.and.Atmospheric.Pollution
Richard Foy
<afre...@epix.net> wrote:
>
>
>You have very strange planes in CA (some with 3 wings?); here in the east
>the contrails come right out of the engines. Or maybe we have the
>strange planes. Whatever...
Three winged airplanes are not so strange. They are just obsolete.
AFAIK Baron von Richoften and his squadron flew 3 winged planes in WW
I. Of course the wings were stacked vertically if that counts. And I
don't remember reading anything about contrails during WW I. :-)
--
"Women feel solidarity in a violent world." -- Judy Kramer
Copyright 1995 Richard Foy All rights reserved. See
URL http://www.he.tdl.com/~hfanoe/cpyrgt_terms.html for terms and condtions.
Carl J Lydick
=In article <hatunenD...@netcom.com>,
=DaveHatunen <hat...@netcom.com> wrote:
=>
=>[...]
=>
=>> Jet engine emissions can often be seen in the atmosphere
=>>in the form of contrails flowing behind the aircraft.
=>
=>Um. You need to get your facts right. Contrails are not from jet
=>engines. B-29s used to create contrails.
=>
=>In fact, they are not from engines at all. They are mostly a wingtip
=>phenomenon, caused by the the altered air physics at the wingtips,
=>where vortices are formed.
=
=Your opinion is very interesting. I quoted directly from what NASA
=has to say about the subject. NASA needs to get its facts straight,
=according to you.
Claire, when an organization issues a press release, the material included in
it will, of necessity, be rather abbreviated. The issuer of the release counts
on journalists doing their own research on the background. That you're quite
incapable of doing that is not in doubt. However, please refrain, in the
future, from blaming your failings as a journalist on NASA.
DaveHatunen
[...]
>I have flown at high altitudes in piston engined aircraft (Mosquitos
>at +25,000ft) and watched the engine exhausts form contrails to the
>horizon. Nothing from the wing tips.
But I CAN'T be wrong! It's only April!
Anway, I certainly bow to your personal experience.
>I have looked at many photographs and movies of high altitude bomber
>flights in WW2 and it is quite clear that they form four contrails per
>aircraft, quite obviously from the four engines. If you count you will
>see that they have but two wing tips. :-)
Trubulence from the engine nacelles?
[...]
DaveHatunen
>In article <NEWTNews.8286081...@epix.net>,
> <afre...@epix.net> wrote:
>>
>>
>>You have very strange planes in CA (some with 3 wings?); here in the east
>>the contrails come right out of the engines. Or maybe we have the
>>strange planes. Whatever...
>
>Three winged airplanes are not so strange. They are just obsolete.
>AFAIK Baron von Richoften and his squadron flew 3 winged planes in WW
>I. Of course the wings were stacked vertically if that counts. And I
>don't remember reading anything about contrails during WW I. :-)
And that wouldbe SIX wingtips...
DaveHatunen
Bill Cornette
>In article <4jr294$o...@crl10.crl.com>, Claire Gilbert <bla...@crl.com>
>writes
>>
>>Your opinion is very interesting. I quoted directly from what NASA
>>
>>Claire Gilbert
>>
>
>Contrails are clearly visible as issuing directly from wing-mounted
>engines on high flying aircraft, or the engine cluster - not the
>wingtips - of aircraft with tail mounted engines. This is easily
>observed just by looking. Wing-tip vortices are sometimes observable
>but at low altitudes and at high wing stress situations where the air is
>spilling off the wing-tip. I have observed these at air-shows, for
>example, where small heavy aircraft do impressive manoeuvres at close
>range. These vortices disipate quite quickly - 5 to 15 seconds - after
>formation.
>
>I once observed NEGATIVE contrails from a low-level aircraft, just taken
>off from a nearby airfield. The conditions were hot, humid with a low
>layer of haze. As the plane passed through this haze, it left four
>channels of clear air.
First, let us look at the origin of the word -
contrails : Condensation trails
To get condensation, you need excess water vapor NOT aerosols or pollution (unless you consider anthropomorphic sources of water as
pollution). As mentioned above, at low altitude, where there is sufficient water vapor in the air (i.e., high relative humidity), t=
he
aircraft can perturb the environment sufficiently (usually at the wing tips) to increase the humidity above 100% and condense out. =
However, this perturbation is very localized and seldom last for more than a few
meters to perhaps a 100 meters. The perturbation passes and the condensed water becomes water vapor again.
Contrails as observed at altitude must have a source of water -- namely
from the hydrocarbon fuel burned by the engine (jet or otherwise). The
excess water from the engine exhaust condenses and almost immediately
freezes (the contrail doesn't start immediately behind the engine, but
usually forms a few 100 meters downstream, where the temperature at altitude is well below freezing). There are a well-known set of=
curves,
called the Appelman curves, that predict the occurence of contrails as
a function of pressure (hence altitude), air temperature, and (to a lesser extent) ambient relative humidity.
Now as to the issue of persistence, for low ambient humidity, a contrail will usually last only a few kilometers -- sublimating int=
o
water vapor. As the ambient relative humidity increases, the contrail
persists and eventually (at sufficiently high humidities) will leach
water vapor out the air, forming high cirrus clouds -- generally, it is
this formation of cirrus clouds that is studied when one is concerned with the impact of contrails on the environment.
None of this addresses the other exhaust products -- primarily carbon
dioxide (a well tuned engine produces limited carbon monoxide, and
commercial airlines have a financial interest in keeping their engines
well tuned; CO is usually only observed when an engine is at idle), and
carbon particles (smoke). These are another issue altogether.
Bill Cornette
Richard Foy
As I understand the facts. Persistant contrails are the result of
engine exhaust, wht ever the type of engine. Transient contrails
occurr from wing tip vortices under certain maneuveres.
The contrails off the wing tips contain nothing that was not in the
air before those contrails were created.
Contrails from engine exhaust contain, air that flows through the
bypass of jet-engines, probably of the same chemical makeup as it was
when it entered the engine. For both jet engines, also, and piston
engines, only, the exhaust contains the products of combustion. These
products contain chemicals which are usually considered pollution.
I very strongly suspect that the pollution study referenced in the
press release is the products of combustion which of course are
intimately misxed with the engine contrails.
Those of us who have seen high flying piston planes, including B-29s,
in movies or from first hand do know that they create contrails from
the engines.
This of course is totally irrelevant to a study regarding pollution
from airplane transportation today.
So why should Claire have looked up any background about enything she
didn't. The infromation she presented was accurate
Richard Foy
>>In article <NEWTNews.8286081...@epix.net>,
>> <afre...@epix.net> wrote:
>>>
>>>
>>>You have very strange planes in CA (some with 3 wings?); here in the east
>>>the contrails come right out of the engines. Or maybe we have the
>>>strange planes. Whatever...
>>
>>Three winged airplanes are not so strange. They are just obsolete.
>>AFAIK Baron von Richoften and his squadron flew 3 winged planes in WW
>>I. Of course the wings were stacked vertically if that counts. And I
>>don't remember reading anything about contrails during WW I. :-)
>
>And that wouldbe SIX wingtips...
>
Right. I can only count not multiply....
afre...@epix.net
> Checked it out. Thanks.
>
Now if the PR person who wrote that had only put a ? at the end of his
title...:-)
afre...@epix.net
> Copyright 1995 Richard Foy All rights reserved. See
> URL http://www.he.tdl.com/~hfanoe/cpyrgt_terms.html for terms and
condtions.
Note: Mr. Foy's copyright does not apply to the included section from my
e-mail.
Scott Nudds
: other times the whole top of the wing might be clouded over. Such
: dissipate very quickly (unlike contrails from exhaust gases, which can
: persist easily for several minutes).
I have seen exhaust contrails grow to become very large, persistant
cloud formations.
--
Carl J Lydick
=>=Your opinion is very interesting. I quoted directly from what NASA
=>=according to you.
=>
=>Claire, when an organization issues a press release, the material included in
=>it will, of necessity, be rather abbreviated. The issuer of the release counts
=>on journalists doing their own research on the background. That you're quite
=>incapable of doing that is not in doubt. However, please refrain, in the
=>future, from blaming your failings as a journalist on NASA.
=
=As I understand the facts. Persistant contrails are the result of
=engine exhaust, wht ever the type of engine. Transient contrails
=occurr from wing tip vortices under certain maneuveres.
Actually, there are three cases:
1) Transient contrails caused by turbulence;
2) Transient contrails caused by exhaust;
3) Contrails which can result in formation of cirrus clouds.
The transient contrails caused by exhaust are more persistent than those caused
by turbulence. However, IF conditions are right for having a contrail trigger
formation of cirrus clouds, then a contrail caused by turbulence will work just
as well as a contrail caused by exhaust. And it was the matter of triggering
cloud formation that I was addressing in my response to Claire's usual
uninformed gibberish.
Jim Scanlon
(edit)
> As I understand the facts. Persistant contrails are the result of
>
> air before those contrails were created.
The vapor trail that forms has different physical characteristics and is
quite different after than before.
The products of combustion are expelled at great heat and pressure into a
critical boundry area and should be considered point sources of pollution.
If the plane flies in the stratosphere, as much of the commercial fleet on
the North Atlantic run does during the winter, combustion products go into
the stratosphere where they will reside longer with different physical
results.
Where I live I frequently see long straight clouds clear across the
horizon which persist for hours, and are caused by aircraft.
Straws add up.
--
199 Canal St #8
San Rafael CA
94901
415-485-0540
afre...@epix.net
:> Carl J Lydick | INTERnet: CA...@SOL1.GPS.CALTECH.EDU | NSI/HEPnet:
SOL1::CARL
:> Actually, there are three cases:
:> 1) Transient contrails caused by turbulence;
:> 2) Transient contrails caused by exhaust;
:> 3) Contrails which can result in formation of cirrus clouds.
What about contrails -> cirrocumulus undulatus clouds? They're a common
sequel here in northeast.
afs
Richard Foy
> 1) Transient contrails caused by turbulence;
> 2) Transient contrails caused by exhaust;
> 3) Contrails which can result in formation of cirrus clouds.
>by turbulence. However, IF conditions are right for having a contrail trigger
>formation of cirrus clouds, then a contrail caused by turbulence will work just
>as well as a contrail caused by exhaust. And it was the matter of triggering
>cloud formation that I was addressing in my response to Claire's usual
>uninformed gibberish.
Thank you for clarifying. However, if I recall the thread correctly
Claire's first post was a NASA press release.
--
"Women feel solidarity in a violent world." -- Judy Kramer
Copyright 1995 Richard Foy All rights reserved. See
Jeffrey R. Secker
Scott Lindstrom <sco...@ssec.wisc.edu> wrote:
>In article <hatunenD...@netcom.com>, hat...@netcom.com (DaveHatunen) writes:
>|> In article <4jr294$o...@crl10.crl.com>, Claire Gilbert <bla...@crl.com> wrote:
>|> >In article <hatunenD...@netcom.com>,
>|> >DaveHatunen <hat...@netcom.com> wrote:
>|> >>
>|> >>
>|> >>> Jet engine emissions can often be seen in the atmosphere
>|> >>
>|> >>
>|> >
>|> >Your opinion is very interesting. I quoted directly from what NASA
>|>
>|> If NASA's postion is that contrails are caused by jet engine
>|> pollutants, it does indeed need to get its facts straight. Perhaps some
>|> PR flack got his facts mixed up...
>|>
>
>Or, perhaps your information is not complete. I refer you to the ol' standby
>Glossary of Meteorology, which allows for two different formation mechanisms for
>condensation trails ("a cloud-like streamer frequently observed to form behind
>aircraft flying in clear, cold, humid air"). One is apparently what NASA and by
>quoting them Claire is describing, i.e., exhaust trails; you seem to be
>describing aerodynamic trails, a rather more scarce occurrence.
>
>--
>Scott S. Lindstrom | The only other sound's
>sco...@ssec.wisc.edu | the sweep of easy
>http://www.ssec.wisc.edu/~scottl/homepage1.html | wind and downy flake
..and note that the primary "exhaust" product that condenses is water.
This "exhaust" trail would be present even if there were no pollutants
in the exhaust and only CO2 and H2O were present.
Jeff Secker
- my own opinions--
Jim Scanlon
formations straight across the sky from horizon to horizon. I see them
often while traveling through the western part of the San Francisco Bay
Area. Sometimes there are several which seem to intersect. Mostly they are
narrow but occasionally they appear to be quite wide. I assume that the
cumulative atmospheric effect of civil/commercial plus military air
traffic from the just above the tropopause down must be considerable. I
also assume that there is some effect when no effect is visible from the
ground.
I remember an article in Science a few years ago showing images of tracks
of ships at sea which were caused by condensation on particulates emitted
from the smoke stacks as they traveled their lonely course. If the
satellites could track the ships on the surface, it seems they should be
able to track planes the sky even more easily as they often fly above
clouds.
Jim Scanlon
Claire Gilbert
Jim Scanlon <jsca...@linex.com> wrote:
>This subject has affected my perception. I now notice long straight cloud
>formations straight across the sky from horizon to horizon. I see them
>often while traveling through the western part of the San Francisco Bay
>Area. Sometimes there are several which seem to intersect. Mostly they are
>narrow but occasionally they appear to be quite wide. I assume that the
>cumulative atmospheric effect of civil/commercial plus military air
>traffic from the just above the tropopause down must be considerable. I
>also assume that there is some effect when no effect is visible from the
>ground.
>
Thought you'd find the following of some interest.
--------------------------------------------------------------
Already, two years ago, I published a short article which
mentions "pseudo-cirrus clouds" from airplane exhaust.
-- Claire Gilbert
TODAY WE SEE FAKE CIRRUS*
I have had many discussions about clouds with Tim, The Talking
Weatherbook of Cloudwatch, a newsletter about the Bay Area
weather.** Weatherbook has meteorological background and has been
a cloud watcher for a long time. He says that the troposphere (the
atmosphere under the stratosphere) is actually getting lower (i.e.,
shrinking) and is colder at the top, causing disappearance of true
cirrus clouds. He believes that what we see today are pseudo-
cirrus clouds created from airplane exhaust. His colleague from
CloudWatch, Dr. Laura, adds that these fake cirrus clouds are also
created from fluffy cumulus clouds which change into a wispy ice
clouds, which look like cirrus ice clouds but do not change
altitude, i.e., they occur lower in the atmosphere than true
cirrus. Weatherbook adds that it is the alta cumulus which
contribute most now to the development of fake cirrus.
*From January-March, 1994, Blazing Tattles
**I believe CloudWatch is no longer being published.
Steinn Sigurdsson
Area. Sometimes there are several which seem to intersect. Mostly they are
narrow but occasionally they appear to be quite wide. I assume that the
cumulative atmospheric effect of civil/commercial plus military air
traffic from the just above the tropopause down must be considerable. I
also assume that there is some effect when no effect is visible from the
ground.
The Hadley crowd mentioned this as an effect they were considering
for next generation models (cloud changes due to plane contrails),
the guesstimate from the floor (forget who), was that traffic
would have to increase by two orders of magnitude (I think) to
be signicant.
The anecdotal observations here do have a rather major bias
in coverage ;-)
afre...@epix.net
:> From: ste...@sandy.ast.cam.ac.uk (Steinn Sigurdsson)
:> The Hadley crowd mentioned this as an effect they were considering
:> for next generation models (cloud changes due to plane contrails),
:> the guesstimate from the floor (forget who), was that traffic
:> would have to increase by two orders of magnitude (I think) to
:> be signicant.
:> The anecdotal observations here do have a rather major bias
:> in coverage ;-)
2) What effects are they considering?
Steinn Sigurdsson
:> From: ste...@sandy.ast.cam.ac.uk (Steinn Sigurdsson)
The "Hadley crowd" is reference to a number of researchers
at the Meteorlogical Office near Reading in the UK.
2) What effects are they considering?
The allusion, as the thread indicates, is to mean changes
in global radiative forcing and concominant climate effects,
this thread was specifically discussing whether airplane contrails
were a significant forcing component (naively cooling due
to albedo changes), my comment was overly cryptic. At a recent
meeting attended by several senior researchers from the Hadley Center
this effect was raised, and it was asserted it had been considered
and was currently negligible globally but of future interest,
particularly if air traffic continued to increase.
afre...@epix.net
In Article<STEINN.96A...@sandy.ast.cam.ac.uk>,
<ste...@sandy.ast.cam.ac.uk> writes:
> The allusion, as the thread indicates, is to mean changes
> in global radiative forcing and concominant climate effects..
Thank you. My ISP's newsserver drops some posts so I'd missed the previous
(several?) message(s) in the thread.
Would you happen to be aware of any organization considering "regional"
effects?