April 03, 2007
The photo above showing vortices wrapped around a pair of parallel condensation trails (contrails) was captured on the morning of December 18, over Amersfoort, Netherlands. This fascinating ringlet, looking like a serpent wrapped about a twig, lasted nearly 40 seconds before finally dissipating.
The swirling pattern sometimes observed in contrails emanate from the tips of the aircraft wings and fuselage. The shape of the aircraft is of course designed to provide maximum lift. So there's lower air pressure on the top of the wing surface and higher pressure on the bottom (Bernoulli effect) -- a result of the curved shape of the wing. Thus, air is drawn up and over the top of the wing tips. These vortices persist for several minutes or more and on occasion become visible as the spinning air sufficiently cools and condenses.