User:Towerman/translation/天气

维基百科,自由的百科全书
馬德拉加拉乔附近的雷暴

天气大气状态的一种表征,反映大气是冷还是热,干还是湿,平静还是狂暴,晴朗还是多云,等等。[1]绝大多数天气现象发生在平流层之下的对流层[2][3]天气通常指每天的温度和降水活动,而气候是指一段长时间内的平均大气状况。[4]如果没有特别指明,“天气”一般指的是地球上的天气。

天气是由不同地方的空气密度(温度湿度)不同所造成的。这些不同根源于各地因纬度不同而不同的太阳角度。The strong temperature contrast between polar and tropical air gives rise to the jet stream. Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow. Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. On Earth's surface, temperatures usually range ±40 °C (100 °F to −40 °F) annually. Over thousands of years, changes in Earth's orbit affect the amount and distribution of solar energy received by the Earth and influence long-term climate and global climate change.

Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes due to differences in compressional heating. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. The atmosphere is a chaotic system, so small changes to one part of the system can grow to have large effects on the system as a whole. Human attempts to control the weather have occurred throughout human history, and there is evidence that human activity such as agriculture and industry has inadvertently modified weather patterns.

Studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark in the Solar System, Jupiter's Great Red Spot, is an anticyclonic storm known to have existed for at least 300 years. However, weather is not limited to planetary bodies. A star's corona is constantly being lost to space, creating what is essentially a very thin atmosphere throughout the Solar System. The movement of mass ejected from the Sun is known as the solar wind.

原因

Stratocumulus perlucidus clouds

On Earth, common weather phenomena include wind, cloud, rain, snow, fog and dust storms. Less common events include natural disasters such as tornadoes, hurricanes, typhoons and ice storms. Almost all familiar weather phenomena occur in the troposphere (the lower part of the atmosphere).[3] Weather does occur in the stratosphere and can affect weather lower down in the troposphere, but the exact mechanisms are poorly understood.[5]

Weather occurs primarily due to density (temperature and moisture) differences between one place to another. These differences can occur due to the sun angle at any particular spot, which varies by latitude from the tropics. In other words, the farther from the tropics you lie, the lower the sun angle is, which causes those locations to be cooler due to the indirect sunlight.[6] The strong temperature contrast between polar and tropical air gives rise to the jet stream.[7] Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow (see baroclinity).[8] Weather systems in the tropics, such as monsoons or organized thunderstorm systems, are caused by different processes.

Because the Earth's axis is tilted relative to its orbital plane, sunlight is incident at different angles at different times of the year. In June the Northern Hemisphere is tilted towards the sun, so at any given Northern Hemisphere latitude sunlight falls more directly on that spot than in December (see Effect of sun angle on climate).[9] This effect causes seasons. Over thousands to hundreds of thousands of years, changes in Earth's orbital parameters affect the amount and distribution of solar energy received by the Earth and influence long-term climate. (see Milankovitch cycles).[10]

The uneven solar heating (the formation of zones of temperature and moisture gradients, or frontogenesis) can also be due to the weather itself in the form of cloudiness and precipitation.[11] Higher altitudes are cooler than lower altitudes, which is explained by the lapse rate.[12][13] On local scales, temperature differences can occur because different surfaces (such as oceans, forests, ice sheets, or man-made objects) have differing physical characteristics such as reflectivity, roughness, or moisture content.

Surface temperature differences in turn cause pressure differences. A hot surface heats the air above it and the air expands, lowering the air pressure and its density.[14] The resulting horizontal pressure gradient accelerates the air from high to low pressure, creating wind, and Earth's rotation then causes curvature of the flow via the Coriolis effect.[15] The simple systems thus formed can then display emergent behaviour to produce more complex systems and thus other weather phenomena. Large scale examples include the Hadley cell while a smaller scale example would be coastal breezes.

The atmosphere is a chaotic system, so small changes to one part of the system can grow to have large effects on the system as a whole.[16] This makes it difficult to accurately predict weather more than a few days in advance, though weather forecasters are continually working to extend this limit through the scientific study of weather, meteorology. It is theoretically impossible to make useful day-to-day predictions more than about two weeks ahead, imposing an upper limit to potential for improved prediction skill.[17]

塑造地球

Weather is one of the fundamental processes that shape the Earth. The process of weathering breaks down the rocks and soils into smaller fragments and then into their constituent substances.[18] These are then free to take part in chemical reactions that can affect the surface further (such as acid rain) or are reformed into other rocks and soils. In this way, weather plays a major role in erosion of the surface.[19]

对人类的影响

对人类社会的影响

New Orleans, Louisiana, after being struck by Hurricane Katrina. Katrina was a Category 3 hurricane when it struck although it had been a category 5 hurricane in the Gulf of Mexico.

Weather has played a large and sometimes direct part in human history. Aside from climatic changes that have caused the gradual drift of populations (for example the desertification of the Middle East, and the formation of land bridges during glacial periods), extreme weather events have caused smaller scale population movements and intruded directly in historical events. One such event is the saving of Japan from invasion by the Mongol fleet of Kublai Khan by the Kamikaze winds in 1281.[20] French claims to Florida came to an end in 1565 when a hurricane destroyed the French fleet, allowing Spain to conquer Fort Caroline.[21] More recently, Hurricane Katrina redistributed over one million people from the central Gulf coast elsewhere across the United States, becoming the largest diaspora in the history of the United States.[22]

The Little Ice Age caused crop failures and famines in Europe. The 1690s saw the worst famine in France since the Middle Ages. Finland suffered a severe famine in 1696–1697, during which about one-third of the Finnish population died.[23]

对个人的影响

The human body is negatively affected by extremes in temperature, humidity, and wind.[24]

预报

2008年的亞洲氣壓圖
北歐衛星雲圖

天气预报将科技应用于预测大气在未来时刻的指定地点的状态。百万年以前人类就一直试图预测天气,直到19世纪才开始有了正式的天气预报。[25][26]天气预报需要收集当前大气状态的定量数据,然后运用我们对大气过程的科学理解来预测大气将如何变化。[27]

开始是完全依靠人力来根据气压变化、当前天气状况以及天空情况做预报,[28][29]现在则使用预报模式预测未来的天气。人力仍然被需要用来挑选最可能优秀的预报模式来做预报,需要考虑模式识别技巧、遥相关、模式效能以及模式偏差。大气的混沌本质、求解描述大气的方程组所需的大量的计算资源、在测量初始情况时所带来的误差、以及对大气过程的仍不完整的理解,种种这些因素使得预报的越早以及预报的时间(预报范围)越长则预报结果越差。集合预报的使用可以帮助我们减小误差和挑选出最可能的结果。[30][31][32]

天气预报有各种各样的终端用户。天气警报被用于保护生命和财产,是重要的预报。[33][34]基于气温和降水的预报对农业很重要,[35][36][37][38]因而也受到股票和期货市场里那些大宗商品交易者的重视。公共事业公司也依靠气温预报来估计未来的需求。[39][40][41]每日里,人们参考天气预报来决定日常的穿戴。因为户外活动会被大雨、雪以及寒风所严重影响,人们依靠预报来计划活动和为坏天气做些预先准备。

影响天气

The aspiration to control the weather is evident throughout human history: from ancient rituals intended to bring rain for crops to the U.S. Military Operation Popeye, an attempt to disrupt supply lines by lengthening the North Vietnamese monsoon. The most successful attempts at influencing weather involve cloud seeding; they include the fog- and low stratus dispersion techniques employed by major airports, techniques used to increase winter precipitation over mountains, and techniques to suppress hail.[42] A recent example of weather control was China's preparation for the 2008 Summer Olympic Games. China shot 1,104 rain dispersal rockets from 21 sites in the city of Beijing in an effort to keep rain away from the opening ceremony of the games on 8 August 2008. Guo Hu, head of the Beijing Municipal Meteorological Bureau (BMB), confirmed the success of the operation with 100 millimeters falling in Baoding City of Hebei Province, to the southwest and Beijing's Fangshan District recording a rainfall of 25 millimeters.[43]

Whereas there is inconclusive evidence for these techniques' efficacy, there is extensive evidence that human activity such as agriculture and industry results in inadvertent weather modification:[42]

The effects of inadvertent weather modification may pose serious threats to many aspects of civilization, including ecosystems, natural resources, food and fiber production, economic development, and human health.[45]

地球上的极端天气

斯洛伐克布拉迪斯拉发清晨的阳光。
同一区域经过小雪在3小时后。

地球上,气温的年平均值在±40°C(从100°F至−40°F)的范围内。整个星球的纬度和气候的大跨度变化范围使得有些地方的极端气温可能会超出这个范围。地球上有记录的最低气温是−89.2 °C(−128.6 °F),发生在1983年7月21日南极沃斯托克站。有史以来的最高气温是57.7 °C(135.9 °F),发生在1922年9月13日阿齐济耶省[46],不过这一纪录被人质疑。最高的年平均气温是34.4 °C(93.9 °F),发生在埃塞俄比亚的達洛爾[47]最低的年平均气温是−55.1 °C(−67.2 °F),发生在南极沃斯托克站[48]在人类定居区的最低年平均气温发生在加拿大境内努納武特地区的尤里卡英语Eureka, Nunavut,达到−19.7 °C(−3.5 °F)。[49]

太阳系内其他星球上的天气

Jupiter's Great Red Spot in 1979.

Studying how the weather works on other planets has been seen as helpful in understanding how it works on Earth.[50] Weather on other planets follows many of the same physical principles as weather on Earth, but occurs on different scales and in atmospheres having different chemical composition. The Cassini–Huygens mission to Titan discovered clouds formed from methane or ethane which deposit rain composed of liquid methane and other organic compounds.[51] Earth's atmosphere includes six latitudinal circulation zones, three in each hemisphere.[52] In contrast, Jupiter's banded appearance shows many such zones,[53] Titan has a single jet stream near the 50th parallel north latitude,[54] and Venus has a single jet near the equator.[55]

One of the most famous landmarks in the Solar System, Jupiter's Great Red Spot, is an anticyclonic storm known to have existed for at least 300 years.[56] On other gas giants, the lack of a surface allows the wind to reach enormous speeds: gusts of up to 600 metres per second (about 2,100 km/h或1,300 mph) have been measured on the planet Neptune.[57] This has created a puzzle for planetary scientists. The weather is ultimately created by solar energy and the amount of energy received by Neptune is only about 1900 of that received by Earth, yet the intensity of weather phenomena on Neptune is far greater than on Earth.[58] The strongest planetary winds discovered so far are on the extrasolar planet HD 189733 b, which is thought to have easterly winds moving at more than 9,600公里每小時(6,000英里每小時).[59]

太空天气

北极光

天气不仅仅发生在行星上。和所有恒星一样,太阳的日冕持续的损耗在太空中,并在整个太阳系产生了一个非常稀薄的大气。太阳喷射出的物质的移动被称为太阳风。太阳表面的大型活动(例如日冕物质抛射)以及太阳风的发生反复无常,使得产生了一个特性与常规天气系统(例如气压和风)相似的系统,常常被称为太空天气。太阳系中日冕物质抛射的范围已经被观察到可以远至土星[60]太空天气也可能会影响到行星大气,有时还会到星球表面。太阳风和地球大气的相互作用可以产生壮观的极光[61]也可能对电敏感系统(如输电系统和无线电信号)产生重大损害。[62]

参见

参考资料

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外部链接


Category:天氣

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