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Polar cyclone
Cyclone

In meteorology, a cyclone refers to an area of closed, circular fluid motion rotating in the same direction as the Earth's rotation. This is usually characterized by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth....
s (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.. 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
Cyclone

In meteorology, a cyclone refers to an area of closed, circular fluid motion rotating in the same direction as the Earth's rotation. This is usually characterized by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth....
, the Coriolis effect
Coriolis effect

In physics, the Coriolis effect is an apparent deflection of moving objects when they are viewed from a rotating reference frame.Newton's laws of motion govern the motion of an object in an inertial frame of reference....
.






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Polar cyclone
Cyclone

In meteorology, a cyclone refers to an area of closed, circular fluid motion rotating in the same direction as the Earth's rotation. This is usually characterized by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth....
s (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.. 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
Cyclone

In meteorology, a cyclone refers to an area of closed, circular fluid motion rotating in the same direction as the Earth's rotation. This is usually characterized by inward spiraling winds that rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth....
, the Coriolis effect
Coriolis effect

In physics, the Coriolis effect is an apparent deflection of moving objects when they are viewed from a rotating reference frame.Newton's laws of motion govern the motion of an object in an inertial frame of reference....
. One center lies near Baffin Island and the other over northeast Siberia
Siberia

Siberia , is the name given to the vast region constituting almost all of North Asia and for the most part currently serving as the massive central and eastern portion of the Russian Federation, having served in the same capacity previously for the Soviet Union from its beginning, and the Russian Empire beginning in the 16th century....
. In the southern hemisphere, it tends to be located near the edge of the Ross ice shelf
Ross Ice Shelf

File:Map-antarctica-ross-ice-shelf-red-x.pngThe Ross Ice Shelf is the largest ice shelf of Antarctica . It is several hundred meters thick. The nearly vertical ice front to the open sea is more than 600 km long, and between 15 and 50 meters high above the water surface....
 near 160 west longitude. When the polar vortex is strong, westerly flow descends to the earth's surface. When the polar cyclone is weak, significant cold outbreaks occur.

Duration and Power

Polar cyclones are climatological features which hover near the poles year-round. They are weaker during summer and strongest during winter. The strength and position of the cyclone shapes the flow pattern across the hemisphere of its influence. An index which is used in the northern hemisphere
Northern Hemisphere

The Northern Hemisphere is the half of a planet that is north of the equator?the word sphere literally means 'half sphere'. It is also that half of the celestial sphere north of the celestial equator....
 to gage its magnitude is the Arctic oscillation
Arctic oscillation

The Arctic oscillation is the dominant pattern of non-seasonal sea-level pressure variations north of 20N latitude, and it is characterized by pressure anomalies of one sign in the Arctic with the opposite anomalies centered about 37-45N....
.

Frequency

Although cyclonic activity is most prevalent in the Eurasian Arctic with approximately 15 cyclones per winter, polar cyclones also occur in Greenland
Greenland

Greenland is a member country of the Kingdom of Denmark located between the Arctic Ocean and Atlantic Oceans, east of the Canadian Arctic Archipelago....
 and the Canadian
Canada

Canada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean....
 Arctic. Polar cyclones can occur at any time during the year. However, summer cyclones tend to be weaker than winter cyclones. 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, is to oil and gas rigs present throughout the Antarctic ocean (sometimes known as the Southern ocean
Southern Ocean

The Southern Ocean, also known as the Great Southern Ocean, the Antarctic Ocean and the South Polar Ocean, comprises the southernmost waters of the World Ocean south of 60th parallel south latitude....
). 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 how polar cyclones might influence 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." The study is expected to be complete by late 2010.

See also