File:Ship-wave-shaped wave clouds induced by Macquarie Island (MODIS 2018-03-05).jpg

English: Sitting in the southwest Pacific Ocean, about halfway between Antarctica and New Zealand, the small and remote Macquarie Island is best known for a small base that houses a handful of scientists and a rugged landscape that provides nesting grounds for a large population of Royal Penguins. Above the landscape, however, the fascination lies in the clouds.

It has been said that the Southern Ocean is the stormiest place on Earth. Winds and waves circle the Antarctic ice usually under a layer of heavy cloud. The complexities of weather, cloud types and formation, precipitation, solar radiation, and their interaction with land forms and ocean currents provide a rich source of interest for scientists. Macquarie Island covers only about 49 square miles (128 sq. km), stretching 21 mi (34 km) long and 3 mi (5 km) wide, but steep mountains reach as high as 1,345 feet (410 m) in the south of the island. The second highest peak on the coastal ridge is Mount Elder, which lies in the northeast, and rises to 1,263 feet (385 m). These peaks are high enough to interface the clouds carried over the islands on roaring winds.

On February 26, 2018, the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite acquired a true-color image which captured the creation and propagation of ship-wave-shaped wave clouds over Macquarie Island.

The long waves in the clouds resemble V-shaped wakes left by moving objects, such as ships, as they pass through standing water. Wind behaves like a fluid, so it is no coincidence that patterns in wind are similar to patterns we see in water. In this case, however, it is not an object moving through stationary water that creates the waves; it is the wind moving around a stationary object. When strongly moving wind slams into a large stationary object (a “bluff body”), the wind is forced around the object. As the wind comes around the object, turbulence is created.

When the turbulence creates regular up and down motion, clouds form when the air moves highest in the atmosphere and cloud disappears at the lowest point, creating a cloud-and-clear pattern. When the cause of the turbulence is small, as in Macquarie Island, the turbulence spreads behind the object, creating a V-shaped wave. When regular up-and-down motion is created, along with the V-shaped spreading, the result is a ship-wave-shaped wave cloud pattern.