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Current Affairs

Polar vortex and India’s weather

Date: 07 March 2020 Tags: Miscellaneous

Issue

Meteorologists have indicated that the frequent wet spell causing heavy rains in North India this season could be a result of record Arctic freeze.

 

Background

The Arctic sea ice cover this winter was at a 10-year high. For a long time, the Arctic ice cover was on a rapid decline due to global warming. 

 

Details

  • The polar vortex or wind circulation is the major cause of the freeze in the Arctic region. The polar vortex is the area of low pressure and cold air that forms near the North or South Pole and is stronger in winter. The polar vortex lets the Arctic cold trapped in the polar region.

  • A strong polar vortex supported by other global factors has caused at least 20 Western Disturbances in North India since January this year.

  • The western disturbance is the low-pressure area over the surface causing changes in pressure, wind pattern, and temperature. This originates in the Mediterranean region which brings sudden rain to the north-western parts of the Indian sub-continent.

Polar vortex

  • A polar vortex is an upper-level low-pressure area lying near one of the Earth's poles. There are two polar vortices in the Earth's atmosphere, overlying the North and South Poles.

  • Each polar vortex is a persistent, large-scale, low-pressure zone less than 1,000 kilometers (620 miles) in diameter, that rotates counter-clockwise at the North Pole and clockwise at the South Pole (called a cyclone in both cases), i.e., both polar vortices rotate eastward around the poles.

  • As with other cyclones, their rotation is driven by the Coriolis effect. The bases of the two polar vortices are located in the middle and upper troposphere and extend into the stratosphere. Beneath that lies a large mass of cold, dense Arctic air.

  • A polar vortex strengthens in the winter and weakens in the summer because of its dependence on the temperature difference between the equator and the poles.