What is the Polar Vortex?

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About Polar Vortex:

The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles.
The polar vortex extends from the tropopause (the dividing line between the stratosphere and troposphere) through the stratosphere and into the mesosphere (above 50 km).
It always exists near the poles, but weakens in summer and strengthens in winter.
The term “vortex” refers to the counter-clockwise flow of air that helps keep the colder air near the Poles.
Many times, during winter in the northern hemisphere, the polar vortex will expand, sending cold air southward with the jet stream.
- Jet streams are relatively narrow bands of strong wind in the upper levels of the atmosphere, typically occurring around 30,000 feet (9,100 meters) in elevation.
This occurs fairly regularly during wintertime and is often associated with large outbreaks of Arctic air in the United States.
This is not confined to the United States. Portions of Europe and Asia also experience cold surges connected to the polar vortex.
By itself, the only danger to humans is the magnitude of how cold temperatures will get when the polar vortex expands, sending Arctic air southward into areas that are not typically that cold.
The Antarctic polar-front jet stream is more uniform and constant than its Arctic counterpart, because Antarctica is surrounded by ocean rather than a mix of land and water.
Cold-air outbreaks, however, do occur in the Southern Hemisphere, but they are less frequent and strike heavily populated areas less frequently.

Q1: What is the stratosphere?

The stratosphere is the layer of Earth’s atmosphere immediately above the troposphere; it extends from a lower boundary (the tropopause) whose altitude varies between about 8 and 16 km to an upper boundary (the stratopause) near 50 km. Ozone, a type of oxygen molecule that is relatively abundant in the stratosphere, heats this layer as it absorbs energy from incoming ultraviolet radiation from the Sun. Temperatures rise as one moves upward through the stratosphere.

Source: TH