Phenomena

Nighttime Streets

Clouds spiral behind the islands of Tenerife and Gran Canaria in this nighttime satellite imagery. Although it’s not entirely unusual to see these von Karman vortex street clouds in the wakes of islands, this is the first time I’ve seen them at night. They form when winds off the ocean are forced up and around rocky islands. Like air moving past a cylinder, the flow forms a swirling vortex off one side of the island, which separates and moves downstream while another forms on the island’s opposite side. When the resulting flow mixes with a cloud layer, we can see the pattern from space. (Image credit: J. Stevens; via NASA Earth Observatory)

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