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| Titel |
Numerical simulations of contrail-to-cirrus transition – Part 2: Impact of initial ice crystal number, radiation, stratification, secondary nucleation and layer depth |
| VerfasserIn |
S. Unterstrasser, K. Gierens |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 4 ; Nr. 10, no. 4 (2010-02-19), S.2037-2051 |
| Datensatznummer |
250008132
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| Publikation (Nr.) |
 copernicus.org/acp-10-2037-2010.pdf |
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| Zusammenfassung |
| Simulations of contrail-to-cirrus transition were performed with an LES
model. In Part 1 the impact of relative humidity, temperature and vertical
wind shear was explored in a detailed parametric study. Here, we study
atmospheric parameters like stratification and depth of the supersaturated
layer and processes which may affect the contrail evolution. We consider
contrails in various radiation scenarios herein defined by the season, time
of day and the presence of lower-level cloudiness which controls the radiance
incident on the contrail layer. Under suitable conditions, controlled by the
radiation scenario and stratification, radiative heating lifts the
contrail-cirrus and prolongs its lifetime. The potential of contrail-driven
secondary nucleation is investigated. We consider homogeneous nucleation and
heterogeneous nucleation of preactivated soot cores released from sublimated
contrail ice crystals. In our model the contrail dynamics triggered by
radiative heating does not suffice to force homogeneous freezing of ambient
liquid aerosol particles. Furthermore, our model results suggest that
heterogeneous nucleation of preactivated soot cores is unimportant. Contrail
evolution is not controlled by the depth of the supersaturated layer as long
as it exceeds roughly 500 m. Deep fallstreaks however need thicker layers. A
variation of the initial ice crystal number is effective during the whole
evolution of a contrail. A cut of the soot particle emission by two orders of
magnitude can reduce the contrail timescale by one hour and the optical
thickness by a factor of 5. Hence future engines with lower soot particle
emissions could potentially lead to a reduction of the climate impact of
aviation. |
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