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Cloud Vortices
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Cloud Vortices

April 16, 2012
Strong northerly winds frequently blow across Greenland, carrying cold, relatively dry polar air out across the Greenland Sea. As the air passes over the moist, warmer waters, conditions are right for cloud formation. As a result, the Greenland Sea is often cloud-filled.

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite passed over the region on April 5, 2012 and acquired this true-color image of a typically cloud-filled sky over the Greenland Sea. It also captured the image of a beautiful von Karman vortex street trailing on the leeward side of Jan Mayen Island.

Jan Mayen Island sits about 500 km (300 mi) east of central Greenland, and about 600 km (400 mi) west of North Cape, Norway, positioning it an area prone to both clouds and wind. The island is dominated by the Beerenberg volcano, which rises 2,277 m (7,470 feet) on the northeastern end. This tall, ice-capped mountain forms a formidable barrier to wind flow. When a strong wind slams against the tall, immovable volcano, the air becomes quite turbulent, and forms a swirling pattern as it passes by. These swirls form a beautiful and predictable pattern, known as a von Karman vortex street.

In the left lower corner of this image, a pattern of feathery white can be seen. This pale veil appears to float above the lower clouds, because the von Karman vortex patterns can be seen beneath the veil in some areas. Viewing the 5 minute swath data used to create this image, the veil can be seen to extend well over Greenland. The color, texture and altitude are suggestive of a large plume of wind-borne snow, possibly mixed with high clouds. It is difficult, however, to differentiate snow from clouds using true-color imagery.

Credits: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC


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