May 22, 2015
This photograph was taken after a pair of perfectly straight contrails become distorted and twisted, and eventually broke into isolated rings. The initial contrails didn't result from exhaust contrails as would commonly be observed from high altitude aircraft. Nor were they vortex contrails as sometimes are seen from the wingtips of a plane, typically at high humidity and low altitude. Rather, they seem to be a hybrid of the two -- wingtip vortices interacting with exhaust contrail to produce a pair of very crisp contrails.
Subsequently, instabilities in the vortices, known after their discoverer as Crow Instabilities, cause them to interact, and ultimately to join. This has the effect of breaking up the long contrail pairs whereby they link up with their partner, creating cloud rings or loops. Only a narrow range of temperature and humidity conditions allow this to occur; the kind of weather just right to go out for a spring walk in the Oxford countryside. Photo taken above Standlake, Oxfordshire, England on April 6, 2015.
Photo details: Camera Model: Canon EOS 550D; Lens: EF 75-300mm f/4-5.6; Focal Length: 125mm; Aperture: ƒ/6.3; Exposure Time: 0.0010 s (1/1000); ISO equiv: 100.