Description

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Context:

Some 60 million people are under weather alerts across 30 states. Seven of them have declared emergencies: Maryland, Virginia, West Virginia, Kansas, Missouri, Kentucky and Arkansas.

What is the Polar Vortex?

It is a large area of low pressure and cold air that swirls like a wheel (counter-clockwise) around both of the Earth's poles. The polar vortex spins anticlockwise around the North Pole with wind speeds of about 155mph (250km/h).

Types

Tropospheric polar vortex: Forms in the lowest layer of the atmosphere, extends from the surface to 10-15 km.
Stratospheric Polar Vortex: Forms about 15 km to 50 km high. Unlike the tropospheric polar vortex, the stratospheric polar vortex disappears during the summer and is strongest in the fall.

How Does the Polar Vortex Cause Extreme Cold?

Aspect	Description
Polar Vortex Weakening	Cold Arctic air moves south, bringing freezing temperatures to regions like the US, Europe, and Asia.
Role of the Jet Stream	A strong polar vortex stabilizes the jet stream, trapping cold air in the north and warm air in the south.
Strong Polar Vortex	Locks bitterly cold, dry air over the Arctic. Acts as a "wind wall" preventing frigid air from moving south.
Weak Polar Vortex	This causes the jet stream to ripple, allowing cold Arctic air to move south, even to regions like Florida (USA).
Impact of High-Pressure Systems	Strong high-pressure systems near the Arctic disrupt the polar vortex. High pressure pushes the polar vortex southward, bringing extreme cold to areas like North America, Europe, and Asia.
Effect on Jet Stream	High-pressure systems disrupt the jet stream, pushing cold air further south, resulting in extreme cold in unusual regions.

Effects of the polar vortex

Arctic Blast: This is a sudden and intense burst of cold air in the US due to a disturbance in the polar vortex that usually keeps cold air confined to the Arctic region.
Extreme Weather Events: A weakened vortex can cause the jet stream to dip south, bringing cold arctic air to lower latitudes and triggering extreme weather events.
Ozone depletion: Trapped cold air in the vortex accelerates ozone depletion, especially over Antarctica, leading to an ozone hole.
Impact on India: A weakened polar vortex results in further disturbances in the west, bringing heavy snowfall to the western Himalayas and cooler temperatures to northern India.

Famous Polar Vortex Events

2013- 2014 Event: This event caused low temperatures and heavy snowfall across Canada and the eastern US.
2021 Texas event: This polar vortex caused freezing temperatures in Texas in February. The low temperature remained for 9 days.

READ IN DETAIL HERE

Polar Vortex

Source:

Indian Express

PRACTICE QUESTION

Q.With reference to the polar vortex, consider the following statements:

It is a large area of high-pressure and hot air that swirls like a wheel around both of the Earth’s polar regions.
The tropospheric polar vortex disappears during the summer and is the strongest during the autumn.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(d) Neither 1 nor 2

Answer: d

Explanation

The polar vortex is a vast area of low-pressure, cold air that rotates like a wheel around both of the Earth’s polar regions. Polar vortices are classified into two types: tropospheric and stratospheric. Hence, statement 1 is not correct.

The tropospheric polar vortex occurs in the lowest layer of the atmosphere, which stretches from the surface to around 10 to 15 km and is where most meteorological occurrences occur.

The stratospheric polar vortex occurs at heights ranging from 15 to 50 kilometres. Unlike the tropospheric polar vortex, the stratospheric polar vortex fades over the summer and peaks in the autumn. Hence, statement 2 is not correct.

Therefore, option (d) is the correct answer.