What is Polar Vortex ? To cut it short, polar vortex is an extremely cold air that generally comes from the wind that is present near the poles i.e. the North Pole and the South Pole. Definition for exam: Polar Vortex is a persistent, large-scale cyclone located near either of a planet’s geographical poles. Most important thing about this is that it consists of extremely cold air bound by a jet stream i.e. they are present at great altitudes in the atmosphere. It has all the properties of a typical cyclone including the property of being a low pressure system. It is strongest during the winter time (of the respective timings of the hemisphere). It generally gets weak or even disappears in the summer. The vortex tends to move very slowly or even stay stationary. Basically an arctic cyclone, it ordinarily spins counterclockwise around the north and south poles. They usually span less than 1,000 kilometers (620 miles) in which the air is circulating in a counter-clockwise fashion (in the Northern Hemisphere). As with other cyclones, their rotation is caused by the Coriolis effect. When the polar vortex is strong, the Westerlies increase in strength. When the polar cyclone is weak, the general flow pattern across mid-latitudes buckles and significant cold outbreaks occur. Ozone depletion occurs within the polar vortex, particularly over the Southern Hemisphere, which reaches a maximum in the spring. Difference between hurricane and polar vortex ? Polar vertex is not like hurricane in the sense that hurricane comes & vanishes after some time. Polar vertex is the normal feature of the polar climate i.e. in short, the weather conditions that are created by this are likely to stay for a longer period. How it has formed ? Over the North Pole, cold air typically forms at night where clear skies allows heat to escape into space. Day after day after day, these pools of air form near the pole. Theres always cold air up there, if the Arctic is left to its own devices. And, because of a multitude of factors, a mass broke south and headed toward the U.S. The jetstream just shifts enough. A high-pressure front just moves in over the upper Midwest, and it just sits in place, and it allows the cold air to spread over the entire upper Midwest. Why is it in news ? It has made it’s presence in United States of America (USA). But still why is it in news ? Polar vortex do shift southwards till the Canada. But this time, it is a very rare phenomenon that this polar vertex has shifted till USA. It has not happened in 20 years. The core of the vortex has actually slipped all the way down over the USA. Vortex is threatening temperatures as low as minus 30 degrees Fahrenheit in the Plains and in the negative 20s and negative teens farther into the Midwest. Reasons for this shift towards south Polar vertex moves during the winter period. But rarely it goes to the USA. Presence of blockage in the form of high pressure system over Eastern Canada. (Air blows from high pressure to low pressure). Chiefly, warmer air builds up over areas such as Greenland or Alaska, and that air forces the colder, denser air southward. Also, weather patterns can create the right conditions for the polar vortex to point south. Why is it dangerous? It is very cold. It has negative temperature readings. Even an exposed flesh of our body or even of any animal can freeze in 5 minutes. Also, many vehicles stop working in such atmosphere. Various economic activities in the country get’s hampered. Without adequate preparation, this polar vertex can be very deadly. It affects people that aren’t used to cold right now. Why it is being so cold? First of all this polar vortex has its source in the North Pole. The high pressure system, paired with the extensive snow cover over southern Canada and the northern United States, is allowing the air to stay very cold. So, When Will the Cold Air Stop? When the strong air from the Eastern Pacific weakens and falls apart, the polar vortex will retreat and go back into place near the North Pole. Until then, temperatures across the northern Plains and Midwest (of USA) will continue to be life-threateningly cold, shattering some all-time low record highs. Ozone Depletion The chemistry of the Antarctic polar vortex has created severe ozone depletion. The nitric acid in polar stratospheric clouds reacts with chlorofluorocarbons to form chlorine, which catalyzes the photochemical destruction of ozone. Chlorine concentrations build up during the polar winter, and the consequent ozone destruction is greatest when the sunlight returns in spring. These clouds can only form at temperatures below about −80 °C (−112 °F). Since there is greater air exchange between the Arctic and the midlatitudes, ozone depletion at the north pole is much less severe than at the south. Accordingly, the seasonal reduction of ozone levels over the Arctic is usually characterized as an ozone dent, whereas the more severe ozone depletion over the Antarctic is considered an ozone hole. - See more at: erewise/current-affairs/polar-vortex-hits-usa_art52d8dc78c2803.html#.UxCz3BSSw6k
Posted on: Fri, 28 Feb 2014 16:07:22 +0000
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