Article Dans Une Revue Atmospheric Chemistry and Physics Année : 2012

The evolution of microphysical and optical properties of an A380 contrail in the vortex phase

Résumé

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 con-trail 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 as-pherical ice particles. In the primary wake, quasi-spherical ice particles were found with concentrations up to 160 cm −3 , mean effective diameter D eff 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 D eff of 4.8 µm, mean (maxi-mum) 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 aspher-ical 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 con-trail ice particles cause less radiative forcing than spherical ones.
Fichier principal
Vignette du fichier
acp-12-6629-2012.pdf (2.18 Mo) Télécharger le fichier
Origine Fichiers éditeurs autorisés sur une archive ouverte
Loading...

Dates et versions

hal-01895872 , version 1 (15-10-2018)

Identifiants

Citer

J.-F. Gayet, Valery Shcherbakov, C. Voigt, U. Schumann, D. Schäuble, et al.. The evolution of microphysical and optical properties of an A380 contrail in the vortex phase. Atmospheric Chemistry and Physics, 2012, 12 (14), pp.6629 - 6643. ⟨10.5194/acp-12-6629-2012⟩. ⟨hal-01895872⟩
86 Consultations
191 Téléchargements

Altmetric

Partager

More