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).
- 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 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.
- 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.
- This occurs fairly regularly during wintertime and is often associated with large outbreaks of Arctic air in the United States.
