What is it and how does the phenomena know as polar vortex form? It is this post`s subject and the cause of extreme cold in some places.
Definition and formation
The polar vortex is a region of low pressure and cold air, stays in Earth’s poles and is surrounded by a jet stream. In North Pole, air flows anticlockwise, forming a vortex. Stays between the middle of troposphere and stratosphere.
This phenomena is not new, stays stronger in the winter and weaker in summer. The vortex motion is caused by Coriolis effect, read the post about cyclones to know more about this effect.
The jet stream separates the pole’s cold air from warmer air. The vortex is not visible to naked eye like tornadoes, storms and lightning. The images in infrared of vortex are taken by meteorological satellites like the AIRS from NASA.
Polar vortex expansion
During the winter in North Hemisphere, the polar vortex lost stability because the jet stream get weaker. When this happens, the vortex is divided and the cold air mass moves to South.
In the regions where the polar vortex expanded, the temperature falls a lot, causing extreme cold. The expansion can last weeks or months. But in Artic stays less cold because masses of warm air move to North. High pressure hot winds can move the vortex to further south.
Polar vortex in South Pole
The vortex in South Hemisphere spins clockwise. Is more stable than the one in Artic, because Antarctica is surrounded by oceans. Therefore, temperature contrast are lower and has less probability of expansion of cold air mass.
In other planets
This phenomena isn’t exclusive of Earth. This is a polar vortex in form of hexagon in Saturn’s north pole, the images were obtained by Cassini in infrared.
This is a double vortex in south pole of Venus. Vortices were also seen in Mars and Neptune.