Polar cyclone

Polar cyclones (also known as "polar vortices", "Arctic cyclones", and "sub-polar cyclones") are vast areas of low pressure which strengthen in the winter and weaken in the summer.Halldór Björnsson. [http://andvari.vedur.is/~halldor/HB/Met210old/GlobCirc.html Global circulation.] Retrieved on 2008-06-15.] . A polar cyclone is a low pressure weather system usually spanning 1,000–2,000 kilometers in which the air is circulating in a counter-clockwise fashion (in the northern hemisphere). The reason for the rotation is the same as any other cyclone, the Coriolis effect. One center lies near Baffin Island and the other over northeast Siberia.Glossary of Meteorology. [http://amsglossary.allenpress.com/glossary/search?id=polar-vortex1 Polar vortex.] Retrieved on 2008-06-15.] In the southern hemisphere, it tends to be located near the edge of the Ross ice shelf near 160 west longitude. [Rui-Rong Chen, Don L. Boyer, and Lijun Tao. [http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0469(1993)050%3C4058%3ALSOAMI%3E2.0.CO%3B2&ct=1 Laboratory Simulation of Atmospheric Motions in the Vicinity of Antarctica.] Retrieved on 2008-06-15.] When the polar vortex is strong, westerly flow descends to the earth's surface. When the polar cyclone is weak, significant cold outbreaks occur. [James E. Kloeppel. [http://www.news.uiuc.edu/scitips/01/12weather.html Stratosheric polar vortex influences winter cold, researchers say.] Retrieved on 2008-06-15.]

Duration

Polar cyclones generally only last for around 2-3 days, and have average wind gusts of under 200km/h for the most severe cases. This falls short of tropical cyclones by a considerable margin, with tropical cyclones sometimes lasting for well over a week, while category 5 cyclones (the most severe official category), can be accompanied by winds of over 300km/h in some cases.

Frequency

Although cyclonic activity is most prevalent in the Eurasian Arctic with approximately 15 cyclones per winter, polar cyclones also occur in Greenland and the Canadian Arctic. Polar cyclones can occur at any time during the year. However, summer cyclones tend to be weaker than winter cyclones.Halldór Björnsson. [http://andvari.vedur.is/~halldor/HB/Met210old/GlobCirc.html Global circulation.] Retrieved on 2008-06-15.] They are not well studied and seldom destructive as they typically take place in sparsely populated areas. The only infrastructure damage that occurs as a direct result of a polar cyclone, are to oil and gas rigs present throughout the Antarctic ocean (sometimes known as the Southern ocean). Some cargo and shipping vessels are also affected, although there are minimal or no reports of losses in recent years as the result of a polar cyclone.

Ongoing studies

The Australian and US Federal Governments recently awarded funding for a study into what the effects of polar cyclones might be on drought in Australia. Scientists hope that the study will gleam a valuable insight into why droughts in Southern Australia are getting worse, and whether or not there is a direct link between polar climate activity, and weather patterns elsewhere. "One of the big problems we have in planning for drought has to do with understanding whether the drought that we are in right now is a climate-change signal or part of a natural cycle. If we want to understand that we need to understand where the rain is coming from." cite web|title="Australian survey into what effects polar cyclones have on drought in Australia"|url=http://www.expertguide.com.au/news/article.aspx?ID=572|accessdate=2008-05-13] The study is expected to be complete by late 2010.

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