Sandy streets over the Atlantic

Thick dust from the Sahara blowing over the ocean off the western coast of Africa encounters the islands of Cape Verde, forming a wake of swirling “vortex streets” visible by satellite.

These swirls are also known as von Karman vortices. When wind encounters the island, the disturbance in the flow propagates downwind in the form of a double row of vortices, which alternate their direction of rotation.

Such effects can be seen anywhere a liquid — including air — flows around a solid body. They are named after engineer and fluid dynamicist Theodore von Kármán.

In the image above, the dust and sand is thick enough to nearly block out some of the islands entirely. See the full scale version here on the Chelys “EOSnap” Earth Snapshot site.