The whirl of Von Kármán vortex streets
On some satellite images taken near mountains or islands you can see spiral patterns – these are called Von Kármán Vortex Streets or Von Kármán Vortices.
Von Kármán Vortices are a physical manifestation of the large scale fluid motion in the atmosphere, and even in oceans. The atmosphere is a fluid in constant motion, which we are usually only aware of when we feel the wind. We rarely have the possibility to observe vortices in this motion, except in satellite images.
In the atmosphere, the vortex streets are easily identified by the characteristic formations in stratocumulus cloud sheets – they appear as spirals
This pattern was first discovered in the atmosphere in 1962, with the help of the American weather satellite TIROS V, until then nobody could detect this feature in the atmosphere.
These vortices normally form in any region where fluid flow is disturbed by an object and usually appear to the lee (the sheltered side) of a mountain or island, when certain atmospheric conditions are present
When wind-driven clouds meet an island they flow around it clockwise and anticlockwise to form the beautiful spinning eddies.
Because these phenomena are so distinctive they can easily be spotted in visible satellite images, which clearly show cloud structures. The areas in the world where these conditions are most frequently encountered are the regions of the Trade Winds. Places to spot Von Kármán Vortex Streets include Canary Islands, Madeira Island, Cape Verde Islands, Guadalupe and Socorro Islands (west of Baja California in the Pacific Ocean) and the Juan Fernandez Islands (off the Chilean coast).
Guadalupe Island is an active island for generating the phenomenon, with a vortex street appearing almost daily in June to August. The world largest Von Kármán Vortex Streets are caused by the Hallasan Volcano, Jeju Island, South Korea, which usually produces them from October to January.
See more images and case studies of Von Kármán Vortex Streets in EUMETSAT’s Image Library.