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					Damas y Señores!
Ladies and Gentlemen!

I would have liked to be with you
today, sharing the beautiful Chilean
skies!
                                       1
In Chile,
where the huge Pacific Ocean
purifies its air,
the topic of this talk may appear
out of place.


                                    2
Contrails used to make us think about
distant places to go!




                                   3
 How about Australia? Its Weather
Bureau proudly presents a Jan. 2001
         calendar photo!




                                 4
Yes, some nature photographers
      are truly delighted:




                                 5
But do contrails really bring fortune?




                                    6
Signs in Sun and Moon!




                         7
Signs in Sun and Moon!




                         8
9
To see the contrails at night requires
     background illumination
 • Here, the full Moon:




                                   10
One can also use aurorae:




                            11
Canada, 2001




               12
-but some would have preferred the
      aurora without contrail !.
  Indeed, IAU/UNESCO already in 1977
  recommended aircraft not to fly close to
  observatories:




                                             13
 Similar desiderata can be found in
           IAU Transactions

Vol. XII (Hamburg), Resolution No. R5
Vol. XVI (Grenoble), Resolution No. R9


                                      14
La Silla (50 cm tel)




                       15
Contrail overhead!




                     16
Mt.Wilson seen from solar tower (web cam!)




                                             17
          IMPORTANT:

  There is little difference between
the life-time of contrails formed on
      the day-sky and at night.


            Only the
    amount of aviation differs!   18
 Contrails may last very long (17
hours measured). They can spread
 into huge sheets of cirrus. In the
 end this becomes subvisible, yet
          IR-detectable.

                                19
            Pic du Midi –
one contrail and much contrail cirrus




                                  20
Mt.Wendelstein in the German Alps
suffers similar contamination, and
    had to end coronographic
   observations in the 1970-ies.




                                21
Stuttgart Observatory, Germany, on light
pollution being amplified by contrails:

”Nachtflüge von Linien- und Charterflugzeugen
sorgen für Emissionen in großen Höhen, die als
Kondensstreifen durch Lichtreflektion zur
Nachtaufhellung beitragen":
Ref: http://www.sternwarte.de/infobl/1999/01



                                               22
   British Amateur Astronomical
Association, 1998, letter to the editor:


 ”Light pollution has largely destroyed
our visual and photographic view of the
  night sky and aircraft condensation
 trails are now destroying the daytime
                 sky.”
                                     23
Good-humoured report from a US star-
          gazing party:

 ”We observed planet Cessna, planet
   Boeing, and comet Contrail !”

                                 24
Now serious: Contrails:
 •   Absorb and scatter starlight
 •   Increase sky-background, in particular urban
 •   Increase seeing (hard to verify experimentally!)
 •   May cause spectroscopic effects (in theory!)




                                                 25
And therefore:
 • Makes relative photometry difficult, in
   particular for wide-field imaging
 • May cause dips of unknown origin in
   single-channel photometry
 • Leaves fewer nights of prime-time!



                                             26
 Our choice:
1. Do nothing, and risk waste of observing time
2. Map the instantaneous contrail position using an all-
  sky imaging detector. Combine with wind data for
  upper troposphere. Take evasive action. (At the same time:
   find NEOs, asteroids, comets, gamma-ray burst counterparts, etc. Never done before!)
This what TASCA is going to do at Tololo.....

3. Re-routing air-corridors (downwind).
4. Aircraft flight altitude selection depending on
  contrail prognosis.
                                                                                     27
Paranal: aircraft seen during night-time, May – October 1997.
Most aircraft seen over the Pacific, at 30 deg max. elevation.
 No systematic record of contrails, however. (A full 2-year
  period has been analysed, but the ’gif’ is not available...)




                                                        28
Contrail dips in solar irradiance




                               29
Who regulates the emission
      of contrails?

        Nobody!




                             30
Environmental Protection Agency
  mentions contrails in just one
  web-document, concluding:
”Currently, there are no regulation addressing contrails and
             their atmospheric effects.” (2001)



                                                               31
    Three layers of contrails!
Rapid growth in european aviation




                               32
              The release, in brief:

•   C12H22 + 17.5 O2 => 12 CO2 + 11 H2O
•   1 kg CH + 3,4 kg O2 => 3,2 kg CO2 + 1,2 kg H2O
•   Annually: multiply by 190 billions, rising 4% p.a.
•   Small, but increasing concentrations of NO, NO2
•   SO2 – depending on fuel; creates aerosols
•   CO, unburned fuel
•   Soot: 1017 particles pr kg fuel; CCN
•   Hot air !
                                                  33
               DIMENSIONS
• duration: above 17 hours;
• width: up to 30 km (for linear contrail);
• length: up to 2000 km (for AWACS cork-screw
  contrail);
• 17.000 airliners of which 4.000 airborne, 10 %
  of which forming contrails at ~10,000 sqm. pr.
  second, or approx. 4 square-kilometer new
  cloud pr. second.
                                              34
A few eye-openers:




                     35
Scotland




           36
37
38
US mid west




              39
1 micron imaging enhancing contrast.




                                 40
One single, 120o tall, IR photo from
 the Alps, showing cirrus aviaticus.




                                 41
Prime reference to the physical
        foundation ...


     ”On conditions for contrail
     formation from aircraft
     exhausts”
    U. Schumann, Meteorol. Zeitschrift, 5, p 4-23 (1996)




                                                           42
                            Recent reports:

• Aviation and the Global Atmosphere, Intergovernmental Panel
  for Climate Change, 1999; http://www.grida.no/climate/ipcc/aviation

• Aviation, aerosols, contrails, and cirrus clouds,
  European Commission, 2001

• On the tradeoff of the solar and thermal infrared
  radiative impact of contrails, G.Myhre og F.Stordal, GRL, in print,
  2001, se http://folk.uio.no/gunnarmy/paper

• --------------- now to results from modelling by DLR:
                                                                        43
1992: contrail cloudiness in % of sky




                                 44
2050 (jump back and forth)




                             45
           When and where?
• (ok, skip it; this is from and for the air force)




                                                 46
Contrails can form and persist under otherwise
clear conditions, anywhere on the Earth.

Military aviation depends on contrail forecasts.
Could easily be applied to civil aviation.
Forecasts are not entirely reliable.

                                            47
Appelmann criterion for contrails




                                48
Vortex tubes form behind wing-tips;
descend by 1 degree tilt, to far below
            flight level.




                                   49
      Måne og rør

            (Moon)
Vortex tubes may persist for two
  minutes, trapping exhausts.



                               50
NOAA satellites very useful for
detections of trails wider than 1
 kilometer. Here is a picture of
     France half covered by
       ”cirrus aviaticus”

                                    51
  British Isles
      and
 Belgium under
     heavy
     cirrus
   aviaticus,
  june 2001.

 Notice absence
 over London !?

 No geometric
  restoration.

noaa&copenhagen
    university
                  52
Chesapeake Bay on Jan 26, 2001
 From space and from ground.
  A rare opportunity of near-
      simultaneous data!



                             53
    Astronauts, who have reported on
          contrails from space:
•   Mr. Guy S. Gardner
•   Mrs. Susan J. Helms (ISS)
•   Dr. Fred W. Leslie
•   Dr. Andy Thomas (MIR)
•   Dr. Jerry M. Linenger (MIR)
•   Dr. Kathryn C.Thornton
•   Dr. Kathryn D. Sullivan
•   Dr. George D. Nelson
•   Dr. Byron K. Lichtenberg
•   Dr. Frank Culbertson (the absence mid Sept 2001!) 54
”Changes in cirrus cloudiness and their
      relationship to contrails”

NATR: no air traffic
NP: North Pacific
NA: North Atlantic

Patrick Minnis et al.,
Nature, 2001

                                   55
         German Weather Bureau,
           45 year time-series

Decline of global radiation   Slow rise in cirrus




                                              56
Remaining 10 frames are just for
   your viewing pleasure!



                               57
’borrowed’ from
  seti @ home”

• All cloudiness in this
  picture is probably
  due to contrails of
  various ages. Cirrus
  Aviaticus!


                           58
      Grand
      Canyon

”Do nothing to mar it’s
 grandeur for the ages
have been at work upon
   it and man cannot
       improve it”
 Ted Roosevelt, 1903
                          59
        Mesa Verde National Park




• US Clean Air Act, section 169A(a): ”Congress
  hereby declares as a national goal the prevention of
  any future, and the remedying of existing
  impairment of visibility in mandatory class I Federal
  areas which impariment results from man-made Air-
  pollution”                                      60
Shenandoah National Forest




                             61
Lassen Vulcanic




                  62
National Park at Vanoise,
      French Alps




                            63
The Baltic Sea @ Rostock




                           64
Naturpark
Nordeifel,
Germany




             65
Dresden, sun-rise




                    66
England, evening




                   67
Dutch Meteorological Institute,
          De Bilt




                                  68
      Muchas Gracias!

(now enjoy your Pisco Sour! )


                                69
Andreas Wicenec kindly provided the pictures from La Silla,
   Marc Sarazin supported aviation statistics at Paranal.




                                                       70
                       References:

      http://www.astro.ku.dk/~holger/IDA/notes.html


         Pedersen, H., ”Aviation and Jet Contrails:
impact on Astronomy”, in Preserving the Astronomical Sky:
           IAU Symp. No. 196, p. 173 (2001).

                                                      71

				
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