May 13, 2021 - Dust and Vortices Behind the Canary Islands

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   Cloud vortices, Saharan Dust
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   Strong winds raised dust from the Sahara Desert and sculpted
   paisley-like patterns in the clouds in mid-May 2021. The Moderate
   Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua
   satellite acquired this stunning true-color image of dust and vortices
   swirling in the atmosphere off of western Africa on May 12.

   Theodore von Kármán, a Hungarian-American physicist, was the first to
   describe the physical processes that create long chains of spiral
   eddies like the ones shown trailing in the wake caused by wind striking
   the Canary Islands. Known as von Kármán vortices, the patterns can form
   nearly anywhere that fluid flow is disturbed by an object. In this
   case, the unique flow occurs as winds rush past the tall peaks on the
   islands. As winds are diverted around these high areas, the disturbance
   in the flow propagates downstream in the form of vortices that
   alternate their direction of rotation.

   On this particular day, wind also carried dust from the Sahara Desert
   offshore, tinting the air south of the Canary Islands a camel-colored
   tan. Some of the dust appears to be caught in the vortices, swirling
   along with the cloud. The slice of silver seen at the top of the image
   and crossing into the vortices is not dust. This is an optical
   phenomenon known as “sunglint”. It occurs when sunlight reflects off
   the surface of the ocean at the same angle that the satellite sensor is
   viewing the surface. The result is a mirror-like specular reflection
   off the water and back to the sensor, which, on smooth water gleams
   with a silver tint.

   Image Facts
   Satellite:  Aqua
   Date Acquired: 5/12/2021
   Resolutions:  1km (2.5 MB),  500m (7 MB),  250m (15.4 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=2021-05-13
 
