File:Cloud Vortices off Juan Fernandez Islands (MODIS 2019-02-06).jpg

English: The combination of a broad cloud deck, strong winds, and tall volcanic peaks can create a spectacular scene when viewed from space. On February 2, 2019, the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite passed over the South Pacific Ocean and acquired a stunning true-color image of a paisley-patterned sky caused by atmospheric turbulence behind the Juan Fernandez Islands.

Sitting roughly 650 km (405 mi) off the west coast of Chile and volcanic in origin, the Juan Fernandez Islands rise precipitously from an east-west-trending submarine ridge. Highly biodiverse and rich in rare, endemic flora and fauna, the islands’ topography runs from steep to extreme, with valleys hidden between tall volcanic ridges. Little of the land can be considered flat.

Isla Alejandro Selkirk is the largest, tallest, and westernmost of the three islands; with the roughly 20-square-mile (52-square-km) island’s summit towering at 5,413 feet (1,650 meters) above sea level. Next in line is Isla Robinson Crusoe, which covers about 19 square miles (48 square kilometers) and reaches to about 3,205 feet (922 meters). The “baby” of the family, Isla Santa Clara is only 0.8 square miles (2.2 square km) in area, and rises to about 1,230 feet (375 m).

When wind blows against the face of the tallest mountains, it flows around the obstacles to create turbulence. Depending on the direction and strength of the wind, the turbulence can take many forms, from gentle swirls or waves to strongly demarcated, repeating eddies such as these Von Karman vortices. While turbulence exists in clear skies, clouds make the motion visible.

In this image, it is easy to see the point where the clouds, driven towards to northwest, encounter large Isla Alejandro Selkirk (west) and Isla Robinson Crusoe (east). The area immediately on the lee side of each island is cloud-free, then the clouds reappear in a paisley-like pattern of Von Karman vortices. Because the cloud deck sits at a higher elevation than the peak on Isla Santa Clara, they pass across that island entirely unimpeded.