NASA - Cloud Vortices Off Saint Helena Island

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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-color 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 kilometers (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

 

 MODIS (or Moderate Resolution Imaging Spectroradiometer) is a key instrument aboard the Terra (EOS AM) and Aqua (EOS PM) satellites. Terra's orbit around the Earth is timed so that it passes from north to south across the equator in the morning, while Aqua passes south to north over the equator in the afternoon. Terra MODIS and Aqua MODIS are viewing the entire Earth's surface every 1 to 2 days, acquiring data in 36 spectral bands, or groups of wavelengths (see MODIS Technical Specifications). These data will improve our understanding of global dynamics and processes occurring on the land, in the oceans, and in the lower atmosphere. MODIS is playing a vital role in the development of validated, global, interactive Earth system models able to predict global change accurately enough to assist policy makers in making sound decisions concerning the protection of our environment.

NASA
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