May 15, 2023 - Swirling Clouds off of Western Africa

Clouds off West Africa
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Fanciful patterns frequently form in the clouds off of western Africa
and the twists and twirls are easily viewed from space. The Moderate
Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra
satellite acquired a true-color image of multiple lines of vortices
spinning across the clouds behind the Canary Islands and Madeira Island
on May 12, 2023. Madeira is north of the Canary Islands and has a
longer design trailing towards the southwest behind it.

These cloud patterns—known as von Kármán vortices—are a familiar
atmospheric phenomenon, especially in areas where trade winds are
prevalent. Physicist Theodore von Kármán, a co-founder of NASA’s Jet
Propulsion Laboratory, was the first to describe the physical processes
that create these chains of spiral eddies.

Von Kármán vortices can form nearly anywhere that fluid flow—including
an air mass, as shown here—is disturbed by a solid object. In this
case, winds blowing across the ocean are disturbed by small but tall
islands that poke above the surface of the North Atlantic. The air
mass, and clouds moving with it, blows around instead of over the
island, creating winding, twirling patterns from the turbulent air flow
behind the islands. The shape and length of the patterns depend on
several factors, including wind speed, cloud cover, and shape of the
object blocking the flow of the wind.

Image Facts
Satellite: Terra
Date Acquired: 5/12/2023
Resolutions: 1km (2.3 MB), 500m (6.4 MB), 250m (5.4 MB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC



https://modis.gsfc.nasa.gov/gallery/individual.php?db_date=2023-05-15

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