09th January 2025 (10 Topics)
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Polar Vortex
Context
A winter storm,caused by the expansion of the polar vortex southwards, hit a large swathe of the country.
What is the Polar Vortex?
- The polar vortex is a large, rotating mass of cold, low-pressure air found around the North and South Poles. It keeps the cold air trapped at the poles. There are two types:
- Tropospheric Polar Vortex: It is located in the lower atmosphere (10-15 km high), where most weather events occur.
- Stratospheric Polar Vortex: It is found much higher (15-50 km), and is stronger in autumn, disappearing in summer.
Why Did the Winter Storm Happen?
- The winter storm in the US was caused by the expansion of the polar vortex southwards. Normally, the polar vortex stays near the poles, but sometimes, it weakens or shifts, allowing cold Arctic air to move southward. This can lead to extreme cold weather even in areas like Florida.
- Under normal conditions, the jet stream—a fast-moving air current in the upper atmosphere—keeps cold air contained in the polar region. The polar vortex helps maintain this jet stream’s position. However, when the vortex weakens:
- The jet stream becomes wavy and unstable.
- Cold air from the polar vortex can break off and move south, leading to extreme weather, including snowstorms and sub-zero temperatures.
- In this case, the weakening of the vortex allowed extreme cold air to move over a large part of the US, causing dangerous weather conditions like snow, heavy winds, and school closures.
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