Hurricane force winds blow off the east coast of Greenland in this Moderate Resolution
Imaging Spectroradiometer (MODIS) image captured by NASA’s Terra
satellite 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 when
there are no clouds over Greenland. The air closest to Greenland’s icecap
cools off rapidly while the layer of air above it stays warm, so the
temperature actually increases with height. Near the coast, air in the
valleys is warmed by the sea. Gravity pulls the cooler air down into the
valleys, which sets up a strong wind blowing from the west-northwest. The
local name for the winds is “piteraq.” They rarely reach as far north as
the city of Ammassalik (also known as Tasiilaq) on Geenland’s southeast
coast, but when they do, they can cause severe damage. The Danish
Meteorological Institute issues special piteraq warnings.
Leif Rasmussen, the retired weather forecaster who noticed the wind pattern
in this image, reports that he has never seen a low-level outflow pattern
as distinct as the one in this image.