STUNNING CLOUD SWIRLS SPOTTED BY SATELLITE

Our Amazing Planet (livescience.com) 27^th November 2012

Alone in the South Atlantic Ocean sits the small volcanic island of Saint Helena. The towering peak of the island disrupts clouds as they pass overhead, creating swirling patterns called von Karman vortices that can be seen by satellites overhead.

The swirling clouds, moving to the northwest over Saint Helena, were snapped by NASA’s Terra satellite on Nov. 15, 2012, according to NASA’s Earth Observatory.

Von Karman vortices are created when a mass of fluid, such as water or air, encounters an obstacle, and creates swirls going in alternating directions. These so-called “Von Karman streets” can be seen in satellite photographs of clouds around the world.

Saint Helena is dominated by Mount Actaeon, which reaches up to 2,680 feet (818 meters), according to the CIA World Fact Book. It’s part of the British overseas territory that includes the islands of Ascension and Tristan da Cunha.

Nobody lived here when it was first discovered by the Portuguese in 1502. British soldiers were stationed on the island during the 17th century, according to the World Fact Book. It became well-known for being the place of Napoleon Bonaparte’s exile from 1815 until his death in 1821, but its importance as a port went down after the opening of the Suez Canal in 1869.

N.A.S.A.

The N.A.S.A. website also carried this image, with the following text:

Cloud Vortices Off Saint Helena Island

NASA’s Terra satellite passed over the South Atlantic Ocean on Nov. 15, 2012, allowing the Moderate Resolution Imaging Spectroradiometer instrument flying aboard to capture this true-colour image of St. Helena Island and the band of wind-blown cloud vortices trailing towards the island’s leeward side.

St. Helena Island is a tiny island lying approximately 1,860 kilometres (1,156 miles) west of Africa. Volcanic in origin, it has rugged topography with steep, sharp peaks and deep ravines. Wind, which can blow unimpeded for hundreds of miles across the ocean, strikes the face of the mountains, and is forced around the unyielding terrain. As it blows around the island, the air spins on the leeward side, much like a flowing river forms eddies on the downriver side of a piling. The spinning wind forms intricate - and mathematically predictable - patterns. When clouds are in the sky, these beautiful patterns become visible from above.

Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team

See the full cloud vortices image… (400Kb)