Thursday, 5 December 2013

Piteraq season,
the most feared in East Greenland

A Piteraq is a cold katabatic wind which originates on the Greenlandic icecap and sweeps down the east coast, commonly in the fall and winter.
Piteraqs blow frequently during the cold season over the Ammassalik fjord towns - Tasiilaq, Kuumiut and Kulusuk.

The word "piteraq" means "that which attacks you" in inuit.

The approaching of a Piteraq is a dreaded cold season hazard: the hurricane-force wind speed can reach 80 m/s (290 km/h). Wind speeds typically reach over 50 m/s. On February 6, 1970, Tasiilaq was hit by the worst documented Piteraq ever in Greenland, reaching an estimated speed of 90 m /s and causing severe damage.

When Piteraq is coming, you can see the mountains starting to smoke and if you look at the ice sheet several hours in advance it becomes blurred.
If this happens, all the towns and villages close completely down, the shutters come on the windows and you are indoors for the day or so it usually lasts.

The town of Tasiilaq is the most subject to Piteraq winds in Greenland.

Piteraqs often occur when there are no clouds, in a fall sunny day.

The air closest to Greenland’s icecap cools off rapidly by contact with the ice so that even in summer the air temperature might be between -20 and -30ºC, while the layer of air above it stays warm, so  actually the temperature 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 suddenly within minutes sets up a strong wind blowing from the west-northwest.

Piteraqs are most intense whenever a low pressure area approaches the coast. Down-slope winds flowing from high elevations of mountains, plateaus, and hills down their slopes to the valleys, planes or sea below are called katabatic winds.

Katabatic is derived from the Greek, meaning "to go down".

It is very cold air from the Davis Strait and Canada that need eastward across the ice sheet, and is associated with a very strong low pressure at Ammassalik sucked out of the Denmark Strait.

Tasiilaq under a piteraq storm

Similar winds are seen in Antarctica, where they give rise to the polar deserts known as the “Dry Valleys”.

Today I found a friendly blog, also about arctic locations and matters, that deserves regular visitation:
Adventures of a Polarphile