Sudden Stratospheric Warming Event

Sudden Stratospheric Warming Event Latest News

Recently, a meteorologist warned of another Sudden Stratospheric Warming (SSW) event that could plunge temperatures below average across parts of the U.S. later this month.

About Sudden Stratospheric Warming Event

• It refers to a rapid rise in stratospheric temperatures that weakens or distorts the polar vortex (a cold-air mass typically stabilized over the Arctic).

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Occurrence of the Event

• It begins with large-scale atmosphere waves (called Rossby waves) getting pushed higher into the atmosphere.
• These waves can “break” (like waves in the ocean) on top of the polar vortex and weaken it. If waves are strong enough, the winds of the polar vortex can weaken so much that they can reverse from being westerly to easterly.
• This leads to cold air descending and warming rapidly.
• It can lead to a displacement or splitting of the polar vortex, so instead of cold air being locked above the polar region, it can push further south into the mid-latitudes.

What is the Polar Vortex?

• It is a large area of low pressure and cold air surrounding both of the Earth’s poles. 
• It 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.
• 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.

 Source: Newsweek