(KNMI) (OZON) (PvV)
Royal Netherlands Meteorological Institute
Section of Atmospheric Composition
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Atmospheric effects of aircraft emissions

Fresh contrail affected by aircraft vortices, observed 12 May 2001, 15h55 UT over Bilthoven.

Present commercial aircraft fly at altitudes of 8-13 km. The emissions from such air traffic can change the atmospheric composition:

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Directly: by emitting carbon dioxide (CO2), nitrogen oxides (NOx = NO + NO2), water vapour, unburnt hydrocarbons, soot, and sulfate particles.
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Indirectly: by a chemical reaction chain similar to smog-formation the greenhouse gas ozone (O3) can be formed. In this reaction chain nitrogen oxides act as a catalyst under the influence of sunlight. As a result of these chemical reations also the concentration of methane (CH4), another greenhouse gas, decreases.

These changes can have effects on climate:

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Ozone, CO2, and water vapour are greenhouse gases and their increase has a warming effect.
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Methane is also a greenhouse gas and its decrease has a cooling effect.
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Aerosols (sulfate particles, soot) could have a cooling effect.
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Contrails formed due to the emission of particles and water vapour can increase the cloud cover in the upper troposphere. This may result in a cooling or heating depending on the size and optical depth of the ice crystals of which the contrails consist. Presently it is believed that contrails lead to a net warming effect.
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There may be changes in (non-contrail) upper level clouds: Most contrails decay after minutes to hours, but some continue to exist and are then not distinguishable anymore from natural cirrus clouds (thin upper level clouds) for the human eye. The climate effect of changes in cirrus cloud cover due to aviation are not well known.

The ozone changes due to aviation also change UV at ground level:

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An increase in the tropospheric ozone column leads to a reduction in the amount of UV radiation reaching the surface.

 


Contrails observed over De Bilt in a high pressure situation.

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Research at KNMI:

Aircraft effects upon the atmosphere are studied by the Section of Atmospheric Composition in cooperation with other international research groups. In the framework of the European Union Environment and Climate Programme project Aeronox first estimates of the effects of emissions of nitrogen oxides by aircraft upon the global atmospheric composition have been made. Within the EU project POLINAT model calculations are confronted with measurements made by a research aircraft in the North Atlantic Flight Corridor.

On the national level we have contributed to the bill Air Pollution and Aviation (Nota Luchtverontreiniging en Luchtvaart - Lulu, 1995). A description of Lulu (in Dutch) is given by the Dutch Civil Aviation Authorities' Environment Dept.(RLD).

An overview of measurements and modelling of the impact of aviation emissions on the atmosphere was given by us in the KNMI Climate Research Department's Biennal Review.

Recent results of our research:

Recently Ernst Meijer, a Ph.D. student of our group, has incorporated a parametrization of aircraft plume processes in our global model. The result is a reduction of about 1/3 of the ozone perturbation due to aircraft NOx-emissions relative to the case where the NOx-emissions are directly emitted into the global model.

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International assessments:
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Statements about the effects of aircraft emissions in the excecutive summary of "The scientific assessment of ozone depletion : 1994" by WMO/UNEP. These have now been outdated by:
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Summary for PolicyMakers (SPM) of the IPCC special report on Aviation and the Global Atmosphere and the corresponding IPCC press release.
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IPCC 1999 Technical reports on supersonic scenarios.
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Press release in Dutch about a symposium held in Amsterdam on 23/24 June 1999 to present the IPCC special report to the aviation sector and policy makers.
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For further reading in Dutch:
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Press release in Dutch about a symposium held in Amsterdam on 23/24 June 1999 to present the IPCC special report to the aviation sector and policy makers.
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Grootschalige verspreiding van vliegtuigemissies in de troposfeer en stratosfeer - relevante fysische processen, Van Velthoven e.a., Tijdschrift Lucht, 12e jaargang, nr. 4, December 1995, p. 129-133.
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Klimaat- en milieueffecten van mondiaal vliegverkeer, Van Velthoven e.a., Nederlands Tijdschrift voor Natuurkunde 62/5, p. 71-75, 19 maart 1996.(samenvatting)
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Zelf rekenen aan strepen in de lucht, D. Olivie, Natuur en Techniek, Juli/Augustus 2000, 58-62.
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For further reading in English:
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The impact of NOx emissions from aircraft upon the atmosphere at flight altitudes 8-15 km, AERONOX, ed. U. Schumann. Office for Publications of the European Commission, Brussels (1995), pp. 471. (ISBN-92-826-8281-1)
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Pollution from Aircraft Emissions in the North Atlantic Flight Corridor (POLINAT), ed. U. Schumann. Air Pollution Research Report 58, Report EUR 16978 EN, Luxembourg: Office for Official Publication of the European Communities (1997) pp. 303.
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Pollution from Aircraft Emissions in the North Atlantic Flight Corridor (POLINAT 2), edited by U. Schumann, Air Pollution Research Report 68, Report EUR 18877 EN, Luxembourg: Office for Official Publication of the European Communities, ISBN 92-828-6197-X (1999) pp. 312.
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The simulation of the transport of aircraft emissions by a three-dimensional global model, Velders et al., Ann. Geophys. 12, 385-393 (1994). (abstract)
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Greenhouse effects of aircraft emissions as calculated by a radiative transfer model, Fortuin et al., Ann. Geophys. 13, 413-418 (1995).
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The passive transport of NOx emissions from aircraft studied with a hierarchy of models, Van Velthoven et al., Atm.Env. 31, 1783-1799 (1997). ( abstract)
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A 3D chemistry transport model study of changes in atmospheric ozone due to aircraft emissions, Wauben et al., Atm. Environm. 31,1819-1836 (1997). (abstract)
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The Effect of the Conversion of Nitrogen Oxides in Aircraft Exhaust Plumes in global Models, Meijer et al., Geophys. Res. Lett. 3013-3016 (1997). (abstract, details)
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Other sites with information about the effects of aircraft emissions:
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The EU POLINAT-2 project (Pollution from Aircraft Emissions in the North Atlantic Flight Corridor)
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NASA's Atmospheric Effects of Aviation Project (AEAP)
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The NASA SONEX project (SASS Ozone and Nitrogen Oxide Experiment). This project has cooperated with POLINAT.
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The NASA SUbsonic Contrails & Clouds Effects Special Study : SUCCESS (at Nasa-Ames, and at Nasa-Langley 1 // 2).
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The International Civil Aviation Organization (ICAO) on : Civil Aviation and the Environment and Aircraft Engine Emissions
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The Air Transport Action Group (ATAG) : Aviation and the Environment report
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Other sites with information about contrails:
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AGU Press Release (21 June 1999) on a paper by Minnis et al. in Geophys.Res.Lett. 26, 13, 1853-1856 (1999).
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Contrail formation and observations
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Satellite observation of contrails at DLR (high res.)
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Contrails and Meteologica by R.C. van Waning show many examples of contrails observed near Amsterdam Airport.
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Jet contrails and climate
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Jet Contrail Studies Using Polarization Lidar
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Copyright © KNMI --- Last modified: Friday, 25-Feb-2005 21:01:06 UTC Please mail any comments or questions to: Peter van Velthoven
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