Why does the polar vortex only occur in polar regions?
The polar stratospheric regions of both hemispheres are surrounded by a narrow band or stream of fast-moving winds very high up blowing from west to east. Similar to the upper tropospheric jet stream, this jet stream develops along a zone of sharp temperature contrasts (or a tight temperature gradient) In this case, it is the temperature gradient that develops along the line between sunlight and the 6-month long, wintertime polar night. This high altitude jet stream is commonly referred to as the polar night jet. The Antarctic polar vortex is the region inside (i.e., poleward) of this jet stream. During winter, the jet stream can reach speeds of over 100 mph at altitudes of 70,000 ft. The Antarctic polar vortex completely circumnavigates the continent of Antarctica. Antarctica during winter, averaging about 183K (-90C or -130F) at 50 hPa (20km) in early August. These temperatures are contained inside the polar vortex region. The winds are predominantly westerly, with a slight north-sou
