Polar Vortex

Context:

A recent winter storm in the United States caused widespread school closures, hazardous road conditions, and power outages.

Polar Vortex:

• Definition: Large low-pressure and cold air system surrounding Earth’s poles.
• Characteristics: Always exists near the poles, stronger in winter, weaker in summer.
• Vortex: Refers to counter-clockwise flow of air, confining cold air near the poles.
• Types of Polar Vortex:
  • Tropospheric Polar Vortex: Found in lowest atmospheric layer (up to 10-15 km), where most weather events occur.
  • Stratospheric Polar Vortex: Found at higher altitudes (15-50 km), strongest during autumn, disappears in summer.
• Key Features:
  • Northern Hemisphere Vortex:
    • Has two main centers: Near Baffin Island, Canada, and in northeastern Siberia.
  • Southern Hemisphere Vortex:
    • Located around the South Pole.
    • Stronger and more stable, less likely to wobble.
• How it works?
  • Constant Spin: Spins counter-clockwise around the North Pole throughout the year.
  • Seasonal Shifts:
    • In summer, sits at higher latitudes.
    • In winter, shifts southward.

How Does the Polar Vortex Cause Extreme Cold?

Polar Vortex:

• When weakened, cold Arctic air moves south, bringing freezing temperatures to regions like the US, Europe, and Asia.

Role of the Jet Stream

• Strong Polar Vortex:
  • Keeps the jet stream stable, trapping cold air in the north and warm air in the south.
  • Polar jet stream locks cold, dry air in place over the Arctic, acting as an unscalable wall.
  • Vulnerable when certain atmospheric conditions arise.
• Weakened Polar Vortex:
  • Makes the jet stream wavy, allowing cold Arctic air to move south, sometimes reaching Florida (U.S.).

Impact of High-Pressure Systems

• High-Pressure Near Arctic:
  • Disturbs the polar vortex.
  • Can push the polar vortex farther south into North America, Europe, and Asia.
  • Disrupts the jet stream, leading to extreme cold in unusual areas.

Impacts of Polar Vortex:

• Arctic Blast: Sudden, intense surge of cold air in the US due to disruptions in the polar vortex, which usually confines cold air to the Arctic region.
• Extreme Weather Events: Weakened vortex causes the jet stream to dip southward, bringing cold Arctic air to lower latitudes and triggering extreme weather events.
• Ozone Depletion: Trapped cold air in the vortex accelerates ozone depletion, particularly over Antarctica, leading to the ozone hole.
• Impact on India: Weakened polar vortex results in more western disturbances, bringing heavy snowfall to the western Himalayas and colder temperatures to northern India.

Source: IE

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Previous Year Question

With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct?
1. The IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
2. An IOD phenomenon can influence an El Nino’s impact on the monsoon.
Select the correct answer using the code given below:

[UPSC Civil Service Exam – 2017 Prelims]

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Answer: (b)

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