Portugal’s Madeira Island, sometimes called “the island of eternal springtime”, rises abruptly out of the North Atlantic about 300 miles (483 km) off the coast of Morocco. Madeira’s tall, blunt mountain peaks are actually the crest of a massive submerged shield volcano which has been created over millennia, starting in the Miocene Epoch and continuing until roughly 700,000 years ago. The island’s location not only ensures a mild, spring-like climate but the prevailing north-east trade winds also guarantee near-constant breezes and frequent cloud cover. When the skies are cloudy, the turbulent trails of the winds’ movement around the mountainous island creates twists and twirls in the clouds.
On July 16, 2020, the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of snake-like swirls of white cloud twisting behind Madeira Island.
This trail of cloud is the visible part of a wind pattern called von Kármán vortices. Such vortices can form nearly anywhere that fluid flow (such as a blowing mass of air) is disturbed by a solid object. In this case, winds blowing across the ocean are disturbed by a small island (Madeira Island) poking high above the surface of the North Atlantic. The air mass, and clouds moving with it, blows around instead of over the island. This movement sets up a spinning pattern in the air behind the island, with one side blowing clockwise while the other spins counter-clockwise. In this case, relatively low wind speed gives a moderate disturbance of the wind and cloud behind the island, leaving a snake-like trail of cloud above the blue waters of the North Atlantic.
Date Acquired: 7/16/2020
Resolutions: 1km (363.5 KB), 500m (940.6 KB), 250m (1.8 MB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC