Hurricane force winds blow off the east coast of Greenland in this Moderate ResolutionImaging Spectroradiometer (MODIS) image captured by NASA’s Terrasatellite on September 20, 2003. What looks like a streamer of snow is probably the surface of the sea reacting to the strong winds, because snow evaporates quickly in the dry arctic air. Further evidence that the streamer is on or close to the surface comes from the shadows that the clouds at sea cast on it. The threadlike structures near the coast are likely made by blowing snow or sea foam.
Hurricane-force winds are not uncommon in the area. They often occur whenthere are no clouds over Greenland. The air closest to Greenland’s icecapcools off rapidly while the layer of air above it stays warm, so thetemperature actually increases with height. Near the coast, air in thevalleys is warmed by the sea. Gravity pulls the cooler air down into thevalleys, which sets up a strong wind blowing from the west-northwest. Thelocal name for the winds is “piteraq.” They rarely reach as far north asthe city of Ammassalik (also known as Tasiilaq) on Geenland’s southeastcoast, but when they do, they can cause severe damage. The DanishMeteorological Institute issues special piteraq warnings.
Leif Rasmussen, the retired weather forecaster who noticed the wind patternin this image, reports that he has never seen a low-level outflow patternas distinct as the one in this image.
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Image courtesy Jeff Schmaltz, MODIS Land Rapid Response Team at NASA GSFC Image interpretation provided by Leif Rasmussen
