South Sandwich Wakes
February 27, 2004
The South Sandwich Islands are a chain of eleven volcanic islands that rise up from the South Atlantic Ocean in an arc that extends roughly 240 miles (400 km) north to south. As shown on the above true-color Moderate Resolution Imaging Spectroradiometer (MODIS) satellite image, the islands are sufficiently high to disrupt the lower tropospheric circulation and formation of cloud patterns. Most of this scene, which was acquired on January 27, 2004, is dominated by low-level stratiform clouds. The wake patterns shown above suggest that the air mass, at least at the level of the mountain peaks, is moving from west to east.
Note that the size of the wakes as well as the angle they form coming off the islands correlates fairly well to the height of the islands. For example, the peak on Zavodovski, the northernmost of the islands, stands at 1,807 feet (551 m), while the peak on Visokoi, the island just south of it, is 3,295 feet (1,005 m) tall. The taller Visokoi peak produces a more substantial wake pattern. Additionally, observe that the wakes produced by the islands are fanning out and forming interference patterns where they meet one another. The clouds in the upper right-hand corner of this scene are higher level cirrus and altocumulus clouds.