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| Titel |
Smart aircraft routing - a possibility for mitigation? |
| VerfasserIn |
H. Mannstein, K. Gierens, A. Waibel, S. Meilinger, A. Seifert, C. Köhler, H. Kühne |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027920
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| Zusammenfassung |
| Air traffic affects the energy balance of the earth in various ways. Emission of CO2 with
atmospheric residence times measured in decades contributes to the greenhouse effect as well
as emission of nitrous oxides, with their impact on ozone and methane chemistry. Soot has a
direct effect on the net radiation and, much more important, is involved the production of
contrails and the triggering of contrail cirrus, which can be visible for several hours. These
artificial clouds are initiated when flying in sufficiently cold and moist air. In total their net
radiative forcing is of the same order of magnitude as the forcing by the emitted CO2. The
impact of contrail cirrus on net radiation results from the conversion of ambient
moisture in ice super-saturated regions into ice crystals and depends strongly on
the conditions of the ambient radiation field. It ranges from a warming at night
or over bright low clouds to cooling during daytime over dark surfaces like the
ocean. For the time being these effects are not at all taken into consideration in
aircraft routing: the production of contrails and contrail cirrus happens by chance.
in.
The dependency of the radiative forcing by contrail cirrus clouds on the weather
conditions opens the possibility for a soft version of geo-engineering: Avoiding
warming (and perhaps also producing cooling) contrails and contrail cirrus by small
changes of the flight routes has the potential to reduce the man-made imbalance in
radiative forcing by a few percent - not much compared to other geo-engineering
strategies, but without any adverse consequences. With the exception of a small
amount of additional fuel usage no other substances have to be brought into the
atmosphere. As contrails are produced only in 10%-20% of the flown distances and
only the warming contrails should be avoided, the impact on the traffic system is
limited.
The basic idea of the project ’Environmentally compatible flight route optimisation’,
funded by the German Ministry for Research and Education is, to predict the time integrated
radiative forcing of a potential contrail cirrus based on the information given by a weather
forecast model and use this information in relation to total forcing of the additionally
emitted CO2 when avoiding to trigger these clouds by choosing other flight levels
or routes within the usual flight route optimisation tools. Operational contraints,
costs and effectivity of such a strategy will be evaluated in the next phase of the
project. |
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