von Karman coud vortices

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These are called von Karman cloud vortices, named after Theodore von Karman, co-founder of the Jet Propulsion Laboratory. These vortices near the Aleutian Islands were photographed by an Expedition 15 crewmember on the International Space Station. The vortices are created by the wind encountering a barrier such as an island, then changing direction and velocity and forming eddies in the wind and subsequently, in cloud patterns. The image was taken almost a year ago, on May 23, 2007 and the location of the image is at 51.1 degrees north latitude and 178.8 degrees west longitude.

In the cloud image above, the islands disturb the wind flow. As a prevailing wind encounters the island, the disturbance in the flow propagates downstream of the island in the form of a double row of vortices which alternate their direction of rotation. The animation below (courtesy of Cesareo de la Rosa Siqueira at the University of Sao Paulo, Brazil) shows how a von Karman vortex develops behind a cylinder moving through a fluid.

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