October 29, 2020 - Cloud Vortices and Dust off Canary Islands

Cloud Vortices and Dust off Canary Islands

Swirling patterns in the cloud cover behind the Canary Islands greeted NASA’s Aqua satellite as it passed overhead in late October 2020. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board that satellite acquired a true-color image of the scene on October 26.

The swirls are caused by wind rushing past the tall volcanic peaks on the Canary Islands. These spiral eddies are known as von Kármán vortices and are a pattern that can form nearly anywhere fluid flow is disturbed by an object. In this case, as winds from the northeast strike the towering mountains, the winds are diverted around these peaks, and the disturbance in the flow of wind propagates downstream in the form of vortices that alternate their direction of rotation. When clouds are present, the movement of the air will be shown in the clouds.

On this particular day, the wind was strong enough to create some eddies, but only for a short distance. Dust from the Sahara Desert is entrained in the clouds that lie nearest the coast of Africa.

Image Facts
Satellite: Aqua
Date Acquired: 10/26/2020
Resolutions: 1km (203.5 KB), 500m (652.7 KB), 250m (1.8 MB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC