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Polar Vortex

1

A polar vortex is an upper level low-pressure area, that lies near the Earth's pole.

Earth is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets, and the only astronomical object known to harbor life.

A low-pressure area, low or depression, is a region where the atmospheric pressure is lower than that of surrounding locations.

Polar Vortex Freezes Parts of US by ABC News

2

There are two polar vortices in the Earth's atmosphere, which overlie the North, and South Poles.

The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface.

Polar Vortex explained in under 120 seconds by BBC News

3

Each polar vortex is a persistent, large-scale, low pressure zone that rotates counter-clockwise at the North Pole, and clockwise at the South Pole.

North is a noun, adjective, or adverb indicating direction or geography.

4

The bases of the two polar vortices are located in the middle and upper troposphere and extend into the stratosphere.

The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere.

The troposphere is the lowest portion of Earth's atmosphere, and is also where all weather takes place.

5

Beneath that lies a large mass of cold, dense arctic air.

6

The vortices weaken and strengthen from year to year.

7

When the vortex of the arctic is strong it is well defined, there is a single vortex and the arctic air is well contained; when weaker, which it generally is, it will break into two or more vortices; when very weak, the flow of arctic air becomes more disorganized and masses of cold arctic air can push equatorward, bringing with it a rapid and sharp temperature drop.

8

The interface between the cold dry air mass of the pole and the warm moist air mass further south defines the location of the polar front.

9

The polar front is centered, roughly at 60° latitude.

10

A polar vortex strengthens in the winter and weakens in the summer due to its dependence on the temperature difference between the equator and the poles.

11

The vortices span less than 1,000 kilometers in diameter within which they rotate counter-clockwise in the Northern Hemisphere, and in a clockwise fashion in the Southern Hemisphere.

12

As with other cyclones, their rotation is driven by the Coriolis effect.

In physics, the Coriolis force is an inertial force that acts on objects that are in motion relative to a rotating reference frame.

In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure.

13

When the polar vortex is strong, there is a single vortex with a jet stream that is "well constrained" near the polar front.

Jet streams are fast flowing, narrow, meandering air currents found in the atmosphere of some planets, including Earth.

14

When the northern vortex weakens, it separates into two or more vortices, the strongest of which are near Baffin Island, Canada and the other over northeast Siberia.

Baffin Island, in the Canadian territory of Nunavut, is the largest island in Canada and the fifth largest island in the world.

Siberia is an extensive geographical region, and by the broadest definition is also known as North Asia.

15

The Antarctic vortex of the Southern Hemisphere is a single low pressure zone that is found near the edge of the Ross ice shelf near 160 west longitude.

16

When the polar vortex is strong, the mid-latitude Westerlies increase in strength and are persistent.

The Westerlies, anti-trades, or Prevailing Westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude.

17

When the polar vortex is weak, high pressure zones of the mid latitudes may push poleward, moving the polar vortex, jet stream, and polar front equatorward.

18

The jet stream is seen to "buckle" and deviate south.

19

This rapidly brings cold dry air into contact with the warm, moist air of the mid latitudes, resulting in a rapid and dramatic change of weather known as a "cold snap".

20

Ozone depletion occurs within the polar vortices – particularly over the Southern Hemisphere – reaching a maximum depletion in the spring.

Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about four percent in the total amount of ozone in Earth's stratosphere, and a much larger springtime decrease in stratospheric ozone around Earth's polar regions.

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