Contrail Tic -Tac -Toe

December 06, 2006


Provided by: John A. Adam, Old Dominion University
Summary authors & editors: John A. Adam

This photo showing criss-crossing condensation trails (contrails) was taken from about 33,000 ft (about 10,000 m) somewhere above the Mid-West U.S. I was traveling from from Calgary, Alberta to Norfolk, Virginia in late May 2006, and as our plane passed underneath this contrail, I estimate that it appeared to swing though an angle of about 60 degrees in about a second. Armed with this rough-and-ready estimate, and a “guess-timated” speed of about 600 mph (approximately 960 km/hr), and some elementary geometry, it appears that the pictured contrail would have been about 1,500 feet (460 m) above us. Amusingly, from this perspective the contrail looks like it's “aimed” at prominent thunderhead in the distance.

Contrails are essentially the “visible breath” of jet exhausts. The hot and humid air from the exhaust interacts with the external or ambient air, which is at a very low temperature and vapor pressure. Provided that the ambient air becomes saturated with water vapor, a linear, cirrus-type cloud will form.

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