Crow Instability in Contrails

August 09, 2011

Crow-1 (2) Crow2b Crow3b

Photographer
: Herbert Raab; Herbert’s Photo Web site
Summary Author: Herbert Raab; Jim Foster

The photos above showing jet condensation trails (contrails) from a passing Boeing 747 were taken from Piberbach, Austria on taken on April 2, 2011. These contrails exhibit a phenomenon known as Crow Instability. Vortices that form within contrails have been observed to occasionally interact with each other, and with Crow Instability, symmetric sinusoidal oscillations develop in such a way to form rings behind the passing aircraft. The instability initiating the formation of these rings may result from small-scale turbulence in the air surrounding the contrails or even slight differences between the density of the contrail air stream and adjacent air. If you happen to notice contrails that have symmetric waves and eventually become loop like, you're likely observing an example of Crow Instability. The lower two photos are close up views.