Thursday, May 2, 2013

Piteraq

The Greenland Piteraq is a violent katabatic wind that usually occurs in autumn and winter. Piteraq is a Greenlandic word, translated it means "what assaulting one", referring to the absolute assault on the senses by a Piteraq.

It originates on the inland ice cap at times of little or no cloud over Greenland and the most regular place for it to occur is to the south of the Ammassalik region where I will be paddling! Fortunately, they rarely reach up as far as Tasiilaq

The air closest to the ice cap is cooled by contact with the ice so that even in summer the temperature might be -20° or -30°C while the layer of air above that stays relatively warm.  Near the coast, air in the valleys is warmed by the sea and rises. Gravity pulls the colder air down into the valleys creating a very strong wind blowing from the west-northwest. Piteraqs are most intense whenever a low pressure area approaches the coast, usually as a depression travelling up the Denmark Strait

Piteraq weather conditions are characterised by an intense blue sky, a very clear and dry atmosphere and intense sunlight. Lenticular clouds perpendicular to the wind direction can often be seen towards the ice cap.

Normally, Piteraq wind speeds reach 100 to 160 kph but on February the 6th, 1970, Tasilaq, where I will be starting my expedition, was hit by a savage Piteraq that registered 324 kph before the instruments were blown away. The temperature was -20°C. The town was utterly destroyed and had to be rebuilt from the ground up.

Since that event, the Danish Meterological Institute has issued special Piteraq warnings. In Tasilaq, a flashing light on a mast beside the church is the first indication of what is coming. Warnings are also broadcast by Kalallit Nunaat Radioa, Greenland's National radio station.

Piteraq winds can even be seen on satellite infra red images as streaks heading out to sea as below. Ammassalik Island is just left of centre at the top of the image.

Jeff Schmaltz, NASA

Piteraq approaching
Carl Skou
Piteraq damage in Tasiilaq 1970