Polar Vortex
- A polar vortex (also known as an Arctic cyclone, sub-polar cyclone, and a circumpolar whirl) is a persistent, large-scale cyclone located near one or both of a planet’s geographical poles.
- On Earth, the polar vortices are located in the middle and upper troposphere and the stratosphere. They surround the polar highs and lie in the wake of the polar front.
- These cold-core low-pressure areas strengthen in the winter and weaken in the summer.
- They usually span 1,000–2,000 kilometers, in which the air is circulating in a counter-clockwise fashion (in the northern hemisphere).
- As with other cyclones, their rotation is caused by the Coriolis effect.
- The Arctic vortex in the Northern Hemisphere has two centres, one near Baffin Island and the other over northeast Siberia.
- In the southern hemisphere, it tends to be located near the edge of the Ross Ice Shelf near 160 west longitude.
- When the polar vortex is strong, the Westerlies increase in strength.
- When the polar cyclone is weak, the general flow pattern across mid-latitudes buckles and significant cold outbreaks occur.
- Ozone depletion occurs within the polar vortex, particularly over the Southern Hemisphere, which reaches a maximum in the spring.
