Polar Vertex

What is Polar Vortex?

It was  during the extremely cold winter of 2014 that the term  Polar Vortex became popular.

  1. The term polar vortex is commonly used to describe the circumpolar vortices that cause severe or unusual weather at high latitudes. However, circumpolar vortices can have many different characteristics and influences on the weather.
  2. Also, far from being unusual or rare, they are actually a fairly common feature of the Earth’s atmosphere, and occur on other planets.
  3. When extreme cold events occur, this is not because of the existence of a polar vortex (which was always there) but rather because the edge of the vortex has shifted or a piece has been stripped off and moved south.
  4. Polar vortices occur in two layers of the atmosphere: the troposphere (the lowest layer, up to 5 miles high at the poles) and the stratosphere (up to 30 miles high). In both cases, they refer to the flow of air from west to east, circling the pole.
  5. These two types of polar vortex occur separately from one another, and occupy different latitudes as well as height ranges.
  6. The stratospheric polar vortex is a seasonal feature of the polar atmosphere, formingin late autumn and disappearing in spring.
  7. However, the tropospheric polar vortex exists all year round, and occurs at lower latitudes in addition to being lower in the Earth’s atmosphere.

Formation of Polar Vortex:

Polar vortices form when a strong temperature gradient forms between low and high latitudes. This happens particularly in winter when the
pole gets much less sunlight than areas closer to the equator.

The temperature gradient and the Coriolis Force, caused by the Earth’s rotation, produces the prevailing ‘westerlies’ in the mid-latitudes, which are stronger in winter because of the stronger temperature gradients. At the North Pole, greater variability in land and sea surface temperatures and elevations result in more waves propagating into the stratosphere, and a weaker and less stable stratospheric p.vortex than at the South Pole.

Polar Vortices and the Climate

The stratospheric p. vortex exerts an important influence on the Earth’s climate.

One of the most obvious effects is ozone depletion. This is caused by chemical destruction by chlorine and bromine from CFCs and other manmade compounds. Polar ozone depletion is linked to chemical reactions taking place within polar stratospheric clouds, which occur
in the stratosphere when the temperature drops below a threshold value.

This effect is particularly strong in the southern hemisphere, where the polar vortex is colder and more stable than northern counterpart. The lower temperatures lead to more chemical destruction while a stable p. vortex means that ozone-depleted air is
not dispersed into middle latitudes.

The formation of the ozone hole leads to an even colder, stronger vortex. This happens because ozone absorbs ultraviolet radiation and warms the stratosphere, so less ozone means lower temperatures, strengthening the vortex and further driving the creation of polar stratospheric clouds.

Important Topics Prelims 2021

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