What is Polar Vortex?

March 28, 2024

The polar vortex circling the Arctic is swirling in the wrong direction after surprise warming in the upper atmosphere triggered a major reversal event recently.

About Polar Vortex:

The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles. It 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.
- This occurs fairly regularly during wintertime and is often associated with large outbreaks of Arctic air in the United States and Canada.
Portions of Europe and Asia also experience cold surges connected to the polar vortex.
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).
Low values of ozone and cold temperatures are associated with the air inside the vortex.

Key Facts about Jet Streams:

Jet streams are narrow bands of strong wind that generally blow from west to east all across the globe.
Earth has four primary jet streams: two polar jet streams, near the north and south poles, and two subtropical jet streams closer to the equator.
What Causes Jet Streams?
- Jet streams form when warm air masses meet cold air masses in the atmosphere.
- The sun doesn’t heat the whole earth evenly. That’s why areas near the equator are hot and areas near the poles are cold.
- So, when Earth’s warmer air masses meet cooler air masses, the warmer air rises higher in the atmosphere while cooler air sinks to replace the warm air.
- This movement creates an air current or wind. A jet stream is a type of air current that forms high in the atmosphere.
Since these hot and cold air boundaries are most pronounced in winter, jet streams are the strongest during both the northern and southern hemisphere winters.
On average, jet streams move at about 110 miles per hour.
They are located about five to nine miles above Earth’s surface in the mid to upper troposphere, the layer of Earth’s atmosphere where we live and breathe.