Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Aviation and the Global Atmosphere
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EXECUTIVE SUMMARY
Although aircraft generally fly in corridors, their atmospheric effects are expected to propagate far beyond those regions.
Other reports in this collection
For subsonic aircraft flying in the troposphere and the lowermost part of the stratosphere, emissions of oxides of nitrogen (NOx ) are the primary cause for the modelcalculated
increase in ozone (O3 ) in the upper troposphere (UT). Emissions of NOx , water vapor (H2O), and sulfate from supersonic aircraft cruising in the stratosphere
are expected to decrease the column abundance of O3 .
The effects of aircraft emissions are strongly dependent on flight altitudes: Emissions in the troposphere and the stratosphere have distinctly different effects on O3 .
Although the global chemical transport models used in this assessment attempt to simulate both the troposphere and the stratosphere, these models have been
developed for simulating either the troposphere or the stratosphere, but not both. Thus, the assessment of O3 impact focuses on subsonic aircraft effects using
tropospheric models and supersonic effects using stratospheric models. This approach is probably valid for supersonic aircraft, which cruise exclusively in the
stratosphere (19 km), but it may be problematic for subsonic aircraft that have a sizable amount of emissions in the lowest levels of the stratosphere (around 12 km at
mid-latitudes). The impact of subsonic emissions on the stratosphere has not been fully evaluated using models and requires further investigation.
Calculations for Subsonic Aircraft Scenarios
Model calculations were designed to assess the effects of added NO x . They concluded that there would be an increase in ozone concentration and a decrease in
methane (CH 4 ) concentration.
NO x -All models compute increases of NO x in the upper troposphere (UT)/lower stratosphere (LS) of 50-150 pptv at 12 km at mid-latitudes for 2015; these increases
are significant compared to the average background levels of 50-200 pptv.
http://www.ipcc.ch/ipccreports/sres/aviation/045.htm (1 von 4)08.05.2008 02:42:16