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Winter Storm and Polar Vortex
Context:
A winter storm in the United States has caused at least five deaths and widespread disruptions, including school closures, dangerous road conditions, and power outages.
More on News:
- The extreme weather is linked to the polar vortex, which has expanded southwards, bringing cold air into much of the United States.
- The storm has affected 60 million people across 30 states, with seven states (Maryland, Virginia, West Virginia, Kansas, Missouri, Kentucky, Arkansas) declaring emergencies.
- The National Weather Service has issued warnings for severe thunderstorms, tornadoes, and hail in certain regions in the coming days.
What Is the Polar Vortex?
- Definition: The polar vortex is a large area of low-pressure, cold air swirling around both of the Earth’s polar regions like a wheel.
- Types of Polar Vortex:
- Tropospheric Polar Vortex – Occurs in the lowest layer of the atmosphere, up to 15 km high, where most weather events happen.
- Stratospheric Polar Vortex – Occurs higher in the atmosphere, between 15 km to 50 km. It disappears during summer and is strongest in autumn.
When Does the Polar Vortex Cause Extreme Cold?
- Weakened Polar Vortex: The North Pole’s polar vortex sometimes weakens and shifts southward from its usual position.
- As it weakens, cold arctic air can migrate southward, bringing chilly winds to regions like the U.S., parts of Europe, and Asia.
- Impact on the Jet Stream: A strong polar vortex keeps the jet stream (a narrow band of strong winds in the upper atmosphere) on a circular path, separating cold air in the north from warm air in the south.
- When the polar vortex weakens:
- The jet stream becomes wavy and unstable.
- High-pressure systems disrupt its path, pushing cold air southward.
- This process can cause unusually cold weather as far south as Florida.
- When the polar vortex weakens:
Impact of Climate Change on the Polar Vortex:
- Ongoing Research: Scientists are actively studying how climate change influences the polar vortex and whether rising global temperatures are causing it to destabilise more frequently.
- Hypothesis of Weakening: As the polar regions warm faster than other parts of the Earth, the temperature contrast between the poles and the equator decreases. This could weaken both the polar vortex and the jet stream, making them more susceptible to disruptions.
- Expert Insights: According to the director of the Meteorology Undergraduate Program at Rutgers University: Global warming weakens the polar vortex and the jet stream, increasing their likelihood of being dislodged southward.
- “The planet isn’t warming uniformly. It’s warming more at the pole, overall decreasing the strength of the polar vortex.”
