File:Cloud Vortices off Cape Verde (MODIS 2020-12-26).jpg

English: Soft swirls of cloud illustrated the pattern of the wind behind the Cape Verdes in late December 2020. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired this true-color image on December 22. These cloud patterns—known as von Kármán vortices—are a familiar atmospheric phenomenon, especially in areas where trade winds are prevalent. Such vortices can form nearly anywhere that fluid flow—including an air mass—is disturbed by a solid object. In this case, winds blowing across the ocean are disturbed by tall mountains on the small islands which poke above the surface of the North Atlantic. As the air strikes each tall mountain, it is forced around the obstruction instead of over it. The resulting turbulence takes the form of spinning air—clockwise on one side of the island and counterclockwise on the other, leaving a trail of twisting whorls on the lee side of the islands. It takes a cover of cloud to make the pattern visible.