July 19, 2013
Photographer: Herbert Raab; Herb's Flickr site
Summary Authors: Herbert Raab; Jim Foster
This photo montage shows the evolution of a contrail in the wake of an Airbus A340 aircraft over Piberbach, Austria, on June 9, 2013. On the top photo, a contrail is forming in the cold, clear air immediately behind the jet plane. In the middle panel, Crow Instability vortices (rope like structures) are taking shape within the more diffuse, cloud-like exhaust trail. The lower photo shows that the rope structures or hybrid contrail and the exhaust trail have become separated. Just how they become so precisely separated within the same airstream is not well understood. However, the larger crystal sizes of the hybrid trails, which sublimate at a slower rate than do the smaller crystals in the exhaust contrail, appear to play a role.
Photo details: Canon EOS 500D camera; Tamron SP 70-300 mm, f/4-5.6 lens, 300mm; f/8; ISO 100. Exposure time in Program mode was 1/640 sec. for the first image, and 1/500 sec. for the second and third images.