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Proceedings Paper

Vortex dynamics behind cruising aircraft studied by a ground-based scanning lidar and airborne in-situ measurements
Author(s): Ralf Sussmann; Horst Jaeger
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Paper Abstract

By LIDAR and CCD camera analysis the geometrical evolution of a vortex phase contrail (descent rate Vd equals 2.7 m/s, vortex separation D equals 47 m, vertical extension (sigma) z equals 140 m after 77 s) is analyzed. The contrail of a four-engine aircraft is showing a diffuse central wake phenomenon. From coincident in situ measurements all relevant meteorological parameters are characterized. Ambient humidity had been close to ice saturation. From this a non-exhaust formation of ice can be excluded. Also the mechanism of non- entrainment of exhaust into the vortices is excluded of being responsible for the observed early onset of the central wake (870 m behind aircraft). The central wake onset originates from early detrainment starting after a 3/4 roll-up period of the vortex. Baroclinic and shear forces do not contribute to the detrainment (imaginary Brunt-Vaisala-frequency N2 equals negative 3 multiplied by 10-5 s-2, shear dS/dz equals negative 0.01 s-1, bulk Richardson number Ri, equals N2/(dS/dz)2 equals negative 0.3). Ambient turbulence had been fully developed with an inertial range and locally isotropic turbulence for wavenumbers k-equals 0.004 - 0.1 radian/m. The eddy dissipation rate (epsilon) equals 7.4 plus or minus 0.5 multiplied by 10-5 m2s-3 exceeds the values found over the North Atlantic flight corridor at cruising altitude by a factor of 1000. Turbulence was identified as the dominating detrainment mechanism.

Paper Details

Date Published: 26 May 1997
PDF: 12 pages
Proc. SPIE 3104, Lidar Atmospheric Monitoring, (26 May 1997); doi: 10.1117/12.275153
Show Author Affiliations
Ralf Sussmann, Fraunhofer-Institut fuer Atmosphaerische Umweltforschung (Germany)
Horst Jaeger, Fraunhofer-Institut fuer Atmosphaerische Umweltforschung (Germany)

Published in SPIE Proceedings Vol. 3104:
Lidar Atmospheric Monitoring
Jean-Pierre Wolf, Editor(s)

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