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The author:(作者)delvpublished in(发表于) 2014/1/10 8:26:54 Why United States great cold of the century China “warm winter“
A colleague of mine asked me, so warm in China this year, 39, Beijing also delayed snow, winter will not winter anymore! While the United States is experiencing very cold over there, isn't it cold all United States. In fact, this correlation is slightly forced. United States cold or warm, cold or warm, China, four kinds of cross-cutting relationships may exist.
In the westerlies, and is often in the form of long-wave atmospheric fluctuations exist, can be as simple as a rope swing circle the earth week, low-high, correspond to the different heating and cooling. These waves are known as long waves, wavelength of more than 3,000 kilometers, straight-line distance between China and more than 10,000 kilometers, so a system difficult to directly affect both Central America, but it's hard to say in two or three, it is not easy from United States weather Chinese because of the weather.
The United States suffered a rare cold, mainly because of the polar vortex (polar vortex), Baja, some into the United States North. Mass of cold air outbreaks such as tidal wave into United States, at this point, can't science under the polar vortex.
The polar vortex, referred to as the polar vortex. Very little due to the solar radiation received during the winter months in the Arctic, the air gets cold, forming a stronghold of cold air. The Poles there is a polar vortex, in theory, they are all over the Poles, the Antarctic Vortex as good as gold. But over land in the northern hemisphere, the polar vortex, not in the Arctic, but about its campaign, can be understood as a scurrying around (though vivid but not strict, please understand). Because of the warm air mass intrusions into the northern hemisphere polar vortex is usually divided into 2-3 Center, very rarely is the 4, if both hit triple arrow, may cause the outbreak of China, us and Europe while cold wave (this is rare).
To sum up, the polar vortex is the headquarters of cold air, sometimes split, forming a few small bastions, whose location determines the distribution of heating and cooling in the northern hemisphere is, of course, the closer the colder. 2008 snowstorm in southern China, 2012 cold wave in Europe and Asia, as well as this year's United States Arctic, are relevant to the South of the polar vortex. So the United States exactly how cold was it?
Local time on January 7 (Tuesday) and the United States more than 50 major meteorological stations recorded the minimum temperature for this period, since the 21st century United States native coldest day. Atlanta and DC of temperatures only has-14.4 ℃, this a temperatures is cities on February 5, 1996 yilai of minimum temperatures; Chicago became "Chicago Siberia", ushered in near 30 years to most cold weather, minimum ondal-27 ℃, zhiqian, Chicago most cryogenic appeared in December 24, 1983, then temperatures for-23.8 ℃; 7th full beauty minimum temperatures records appeared in Minnesota of embarrass, for-37 ℃.
But as of Wednesday, the United States does not have any sites to break observing minimum temperature records in the history, just past a dozen years in the challenge of low value.
Calendar year from December 1 to January 7 United States local temperature statistics, this year is just United States the coldest winter in more than 20 years. In late January 1985, polar vortex appeared in United States, Maine, when colder than this year, and this year only United States cold year, prominent short-time temperature has fallen, but only 3-4 days in duration, and soon usher in a warmer. So really defined as United States history is relatively cold winter forced. "The cold wave of the century" in the "century" If the word refers to is the 21st century, it was only about a dozen years, and word games.
Return to the topic of the polar vortex, as you can see, in January this year, two in the northern hemisphere polar vortex, polar vortex polar vortex in North America and Northern Asia, respectively, compared with stronger polar vortex and South of North America, polar Cold air more transfer to the North. Northern polar vortex is weak, cause this winter since the invasion of cold air is less, strength is low. Later remains to be seen whether this pattern be adjusted, it is difficult to give a definitive conclusion.
一个同事问我，今年中国这么暖，哪有点三九的样子，北京也迟迟不雪，冬将不冬了！而美国那边正在经历极寒，是不是冷空气都跑美国去了。实际上，这种关联略牵强。美国冷或暖、中国冷或暖，四种交叉关系都可能存在。
在西风带中，大气波动往往以长波形式存在，可以简单的看作环绕地球一周甩动的绳子，有低有高，对应着冷暖的不同。这种波被称为长波，一般波长在3000公里以上，而中美之间的直线距离超过1万公里，所以一个系统很难同时直接影响到中美，但两个或三个就不好说了，这也是不能简单从美国天气推断中国天气的原因。
这次美国遭遇罕见极寒，主要原因是极地涡旋(polar vortex)南下，部分进入美国北部。大规模的冷空气爆发如潮水般侵入美国，说到这里，就不能不科普下极地涡旋。
极地涡旋，简称极涡。由于北极地区在冬季得到的太阳辐射极少，空气越来越冷，形成了冷空气的大本营。南北两极各存在一个极涡，理论上，它们都在极地上空，这点南极涡比较乖。但北半球陆地多，极涡不在北极，而是绕其运动，可理解为四处乱窜(虽生动但不严谨，请谅解)。由于暖气团的侵入，北半球极涡通常又会分裂为2-3个中心，极少情况是4个，如果同时出击，万箭齐发，可能会造成中美欧同时爆发寒潮(这种情况极少见)。
综上所述，极涡是冷空气大本营，有时会分裂，形成几个小本营，其位置决定了北半球的冷暖分布情况，当然是越靠近越冷。2008年我国南方雪灾，2012年欧亚寒潮以及今年美国极寒，都与极涡偏南有关。那么这次美国到底有多冷呢？
当地时间1月7日(周二)，美国超过50个主要气象观测站点记录了这段时期的最低气温，为21世纪以来美国本土最冷一天。亚特兰大市和华盛顿特区的气温仅有-14.4℃，这一气温也是两市1996年2月5日以来的最低气温；芝加哥成为“芝伯利亚”，迎来近30年来最寒冷天气，最低温达-27℃，之前，芝加哥最低温出现在1983年12月24日，当时气温为-23.8℃；7日全美最低气温纪录出现在明尼苏达州的恩巴勒斯，为-37℃。
但截至到周三，美国并没有任何站点打破观测史上最低气温纪录，仅仅是挑战了下过去十几二十年的低值。
从历年12月1日-1月7日美国本土气温统计看，今年仅仅是美国20多年来最冷的冬天。1985年1月下旬，极地涡旋出现在美国的缅因州，那次比今年还要更冷，今年只能算是美国比较冷的一年，突出表现在短时气温剧烈下降，但持续时间仅为3-4天，很快迎来大回暖。所以真要定义成美国史上最冷冬天是比较牵强的。“世纪寒潮”中的“世纪”二字如果指代的是21世纪，那不过是十几年的事，文字游戏罢了。
再次回到极涡的话题，可以看到，今年1月，北半球存在两个极涡，分别是北美极涡和北亚极涡，相比之下，北美极涡更强大且偏南，极地冷空气更多向北美输送。而北亚极涡较弱，导致今冬以来，侵入我国的冷空气次数少、强度弱。后期这种格局是否会调整还有待于观察，很难给一个确定性的结论。
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