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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 12, 6629-6643, 2012
www.atmos-chem-phys.net/12/6629/2012/
doi:10.5194/acp-12-6629-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research Article
26 Jul 2012
The evolution of microphysical and optical properties of an A380 contrail in the vortex phase
J.-F. Gayet1, V. Shcherbakov1,2, C. Voigt3,4, U. Schumann3, D. Schäuble3, P. Jessberger3, A. Petzold3, A. Minikin3, H. Schlager3, O. Dubovik5, and T. Lapyonok5
1LAMP, UMR6016 CNRS/Université Blaise Pascal, Clermont-Ferrand, France
2LAMP, Institut Universitaire de Technologie d'Allier, Montluçon, France
3Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany
4Institut für Physik der Atmosphäre, Johannes Gutenberg Universität Mainz, Mainz, Germany
5LOA, UMR 8518 CNRS/Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France

Abstract. A contrail from a large-body A380 aircraft at cruise in the humid upper troposphere has been probed with in-situ instruments onboard the DLR research aircraft Falcon. The contrail was sampled during 700 s measurement time at contrail ages of about 1–4 min. The contrail was in the vortex regime during which the primary wake vortices were sinking 270 m below the A380 flight level while the secondary wake remained above. Contrail properties were sampled separately in the primary wake at 90 and 115 s contrail age and nearly continously in the secondary wake at contrail ages from 70 s to 220 s. The scattering phase functions of the contrail particles were measured with a polar nephelometer. The asymmetry parameter derived from these data is used to distinguish between quasi-spherical and aspherical ice particles. In the primary wake, quasi-spherical ice particles were found with concentrations up to 160 cm−3, mean effective diameter Deff of 3.7 μm, maximum extinction of 7.0 km−1, and ice water content (IWC) of 3 mg m−3 at slightly ice-subsaturated conditions. The secondary and primary wakes were separated by an almost particle-free wake vortex gap. The secondary wake contained clearly aspherical contrail ice particles with mean Deff of 4.8 μm, mean (maximum) concentration, extinction, and IWC of 80 (350) cm−3, 1.6 (5.0) km−1, and 2.5 (10) mg m−3, respectively, at conditions apparently above ice-saturation. The asymmetry parameter in the secondary wake decreased with contrail age from 0.87 to 0.80 on average indicating a preferential aspherical ice crystal growth. A retrieval of ice particle habit and size with an inversion code shows that the number fraction of aspherical ice crystals increased from 2% initially to 56% at 4 min contrail age. The observed crystal size and habit differences in the primary and secondary wakes of an up to 4 min old contrail are of interest for understanding ice crystal growth in contrails and their climate impact. Aspherical contrail ice particles cause less radiative forcing than spherical ones.

Citation: Gayet, J.-F., Shcherbakov, V., Voigt, C., Schumann, U., Schäuble, D., Jessberger, P., Petzold, A., Minikin, A., Schlager, H., Dubovik, O., and Lapyonok, T.: The evolution of microphysical and optical properties of an A380 contrail in the vortex phase, Atmos. Chem. Phys., 12, 6629-6643, doi:10.5194/acp-12-6629-2012, 2012.
 
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