Ozone depletion occurs within the polar vortices – particularly over the Southern Hemisphere – reaching a maximum depletion in the spring.
The polar vortex was first described as early as 1853. The phenomenon's sudden stratospheric warming (SSW) develops during the winter in the Northern Hemisphere and was discovered in 1952 with radiosonde observations at altitudes higher than 20 km.
The phenomenon was mentioned frequently in the news and weather media in the cold North American winter of 2013–2014, popularizing the term as an explanation of very cold temperatures.
A deep freeze that gripped much of the United States and Canada in late January 2019 has been blamed on a polar vortex. The US National Weather Service warned that frostbite is possible within just 10 minutes of being outside in such extreme temperatures, and hundreds of schools, colleges and universities in the affected areas were closed. Around 21 people died in US due to severe frostbite. States within the midwest region of the United States had windchills just above -50°F (-45°C), which is colder than the frozen tundra and Antarctica.
The Polar vortex has also thought to have had effects in Europe. For example, the 2013–14 United Kingdom winter floods were blamed on the Polar vortex bringing severe cold in the United States and Canada. Similarly, the severe, brutal cold in the United Kingdom in the winters of 2009/10 and 2010/11 were also blamed on the Polar vortex.
Polar cyclones are low-pressure zones embedded within the polar air masses, and exist year-round. The stratospheric polar vortex develops at latitudes above the subtropical jet stream. Horizontally, most polar vortices have a radius of less than . Since polar vortices exist from the stratosphere downward into the mid-troposphere, a variety of heights/pressure levels are used to mark its position. The 50 mb pressure surface is most often used to identify its stratospheric location. At the level of the tropopause, the extent of closed contours of potential temperature can be used to determine its strength. Others have used levels down to the 500 hPa pressure level (about above sea level during the winter) to identify the polar vortex.
Polar vortices are weakest during summer and strongest during winter. Extratropical cyclones that migrate into higher latitudes when the polar vortex is weak can disrupt the single vortex creating smaller vortices (cold-core lows) within the polar air mass. Those individual vortices can persist for more than a month.
Volcanic eruptions in the tropics can lead to a stronger polar vortex during winter for as long as two years afterwards. The strength and position of the polar vortex shapes the flow pattern in a broad area about it. An index which is used in the northern hemisphere to gauge its magnitude is the Arctic oscillation.
Geisha
The term 'geisha' is made of two Japanese words, () meaning 'art' and () meaning 'person who does' or 'to be employed in'. The most literal translation of geisha to English is 'artist'. Geisha are respected as artists and performers: it is difficult to become one.
Kyoto is the city with the most strict geisha traditions. Geisha have worked there for the longest time. Becoming a professional geisha can take up to five years of training in Kyoto.
Apprentice geisha are called . This name is made of the Japanese words () meaning 'dancing' and () meaning 'child'. wear white make-up called and long-sleeved kimono of many bright colours. in some places wear a belt, called an , that is up to long. Many wear fancy hairstyles made with their own hair, though in some places wear wigs. Full geisha wear simpler kimono, and only use white make-up at special times. Geisha also wear wigs, and their kimono belt is much shorter.
There are also geisha in other cities, though there are differences. In Tokyo, becoming a full geisha takes from six months to a year. Geisha apprentices in Tokyo are called , which means 'half jewel' or 'half pay'. Apprentice geisha in Tokyo are also called , which means 'one who serves (alcohol)'. Geisha in Tokyo are normally older than geisha in Kyoto.
Many geisha still live in traditional geisha houses called in neighborhoods called which means 'flower town'. Older geisha who are successful may have their own home. A geisha always needs to be registered to a geisha house in order to work.
The world that geisha are a part of is called , which means 'the flower and willow world'. One very famous geisha, , said this is because "[a] geisha like a flower, beautiful in her own way, and like a willow tree, gracious, flexible, and strong".
Geisha are considered to be cultural icons of Japan.
Before the geisha appeared there were some women who worked as artists and entertainers. In the Heian Period (794-1185), some women entertained people at the Imperial Court through singing and dancing, and these women were known as .
Later on, women who worked as prostitutes and courtesans entertained men in the red-light districts of Japan. In 1589, authorized the building of a neighborhood in Kyoto, closed from the outside with walls. It was called , and it was dedicated to pleasure. was established as a red-light district officially in 1640, and became one of three areas in Japan where people could legally practice prostitution; the other two areas were in Tokyo, which had been established in 1617, and in Osaka.
These areas were known as , and they were the only places where women were allowed to be prostitutes. Courtesans were collectively called , and they were very expensive. entertained men with singing, dancing, poetry, music and conversation as well. The highest ranking were called , and these women did not engage in prostitution like other . Instead, they would have one or two rich clients act as their patron, and these men would pay a lot of money to be entertained by the they were a patron of.
Geisha only appeared much later, in the Tokugawa period. Originally, geisha were men, who travelled throughout the red-light districts, entertaining clients with music, dancing and poetry. These men were known as geisha, but were also called , and because they played the , a Japanese drum.
Male geisha were very low-class entertainers, but were thought to be upper class. Every man who wished to be with an had to follow difficult rituals and etiquette, as well as having enough money to pay for her time. Because of this, only the richest nobility got to be entertained by . Because of this, many tea houses () appeared outside , offering entertainment that was not offered inside . At some of the tea houses, some women practiced cheaper prostitution; these women were called . However other women, who were called ('dancing girls'), acted as dancers and musicians. These women soon became very popular. They started calling themselves 'geisha', like the male artists who worked in .
By about the year 1700, female geisha had become much more popular than male geisha. A few years later, almost all geisha were women.
The government made laws that prohibited geisha from working as prostitutes, and only gave them permission to act as entertainers. One of these laws said that they had to tie their (sash) in the back, as wore theirs at the front as a sign that they were available for sex. Geisha had to wear simpler hairstyles, less hair accessories, less make-up and simpler kimono. If an accused a geisha of stealing her customers, the geisha would be investigated.