A polar vortex, also known as a circumpolar vortex is a large area of cold, rotating air that surrounds both of the Earth’s polar regions. It always exists in poles, but strengthens in winters and weakens in summers.
The term ‘vortex’ in the circumpolar vortex refers to the counterclockwise flow of air that helps to keep the colder air near the poles. Most of the time during winters in the northern hemisphere, the polar vortex will expand, sending cold air southwards through the jet stream. This generally occurs during winters and is often associated with the large outbreaks of Arctic air in the United States.
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Polar Vortex Meaning
Polar vortex, or circumpolar vortex, the polar low, polar cyclone is a large area of persistent low pressure generally located above each of the Earth’s polar regions and containing a mass of extremely cold air. The altitude of this cyclone extends from the middle of the troposphere ( the lowest level of Earth’s atmosphere which spans the region from the surface up to 10 - 18 km [ 6 -11 miles high] km into the stratosphere (the atmospheric layer that extends from 10 -18 km to about 50 km [ 30 miles] high.
The cold air is contained within the polar vortex by the polar front Jet stream. The strength of the polar vortex changes with the season. It is strongest during the winter season in each hemisphere when the Equator is at greatest and temperature contrast between the poles. It may be weaker or entirely diminished during the warmer months of the year.
Polar cyclones, also known as arctic cyclones or polar vortices are very large areas of low pressures. The term polar low should not be confused with the term polar cyclones. Polar cyclones are generally 1000 to 2000 kilometers wide in which the air is moving in the spiral counterclockwise in the northern hemisphere. The reason for this rotation is similar to tropical cyclones, the Coriolis effect. They also exist in the regions such as the Eurasian Arctic area, Greenland, and northern Canada with about 15 cyclones per winter.
Polar cyclones can occur at any time of the year, although summer polar cyclones are weaker than the ones that occur in the winters.
Strength and Duration of Polar Vortex
The strength and duration of the polar vortex are as follows:
Polar vortices or polar cyclones are weakest during summers and strongest during the winters.
During the volcanic eruptions in the tropics, a polar vortex will be strengthened and can stay that way for 2 years after the initial eruptions.
Extratropical cyclones that emigrate into the higher latitudes when the polar vortex is weaker can disturb the single vortex creating small vortices within the polar air mass. Those individual vortices can continue for more than a month.
The Antarctic polar vortex is more pronounced and persistent than the Arctic polar vortex.
The climate anomalies La Nina significantly strengthen the polar vortices.
Strengthening the polar system within the troposphere that cools down the poles, intensifying the polar vortex.
The Northern polar vortex comes about between Mid March Mid May. This event marks the transition from the winter season to the spring season. Hydrological cycles, growing seasons of vegetation, and overall ecosystem productivity are highly impacted by these events.
The same transition also impacts sea ice, zone, air temperature, and cloudiness immensely.
Early and late polar break events have occurred due to the variation in stratospheric flow structure and the upward spreading of planetary waves from the troposphere.
When the polar break up is early, there is one warning period from late February to middle March whereas when the polar break up is late, there are two warning periods, one in January and the other in March.
Sometimes, a mass polar vortex breaks off before the end of the final warning period. If large enough it can move into Canada and the Midwestern, Central, Southern, and Northeastern United States.
Polar Vortex UPSC Facts and Information
Following are some of the polar vortex UPSC facts and information:
A polar vortex on Earth is usually in the middle and upper troposphere and stratosphere.
The Arctic vortex has two main centers: one is over Baffin Island, the other is over Northeastern Siberia.
Polar vortex and weather impacts due to stratospheric warnings.