使用者:Towerman/translation/天氣

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馬德拉加拉喬附近的雷暴

天氣大氣狀態的一種表徵,反映大氣是冷還是熱,干還是濕,平靜還是狂暴,晴朗還是多雲,等等。[1]絕大多數天氣現象發生在平流層之下的對流層[2][3]天氣通常指每天的溫度和降水活動,而氣候是指一段長時間內的平均大氣狀況。[4]如果沒有特別指明,「天氣」一般指的是地球上的天氣。

天氣是由不同地方的空氣密度(溫度濕度)不同所造成的。這些不同根源於各地因緯度不同而不同的太陽角度。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]

對人類的影響

對人類社會的影響

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]

對個人的影響

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

預報

2008年的亞洲氣壓圖
北歐衛星雲圖

天氣預報將科技應用於預測大氣在未來時刻的指定地點的狀態。百萬年以前人類就一直試圖預測天氣,直到19世紀才開始有了正式的天氣預報。[25][26]天氣預報需要收集當前大氣狀態的定量數據,然後運用我們對大氣過程的科學理解來預測大氣將如何變化。[27]

開始是完全依靠人力來根據氣壓變化、當前天氣狀況以及天空情況做預報,[28][29]現在則使用預報模式預測未來的天氣。人力仍然被需要用來挑選最可能優秀的預報模式來做預報,需要考慮模式識別技巧、遙相關、模式效能以及模式偏差。大氣的混沌本質、求解描述大氣的方程組所需的大量的計算資源、在測量初始情況時所帶來的誤差、以及對大氣過程的仍不完整的理解,種種這些因素使得預報的越早以及預報的時間(預報範圍)越長則預報結果越差。集合預報的使用可以幫助我們減小誤差和挑選出最可能的結果。[30][31][32]

天氣預報有各種各樣的終端用戶。天氣警報被用於保護生命和財產,是重要的預報。[33][34]基於氣溫和降水的預報對農業很重要,[35][36][37][38]因而也受到股票和期貨市場裡那些大宗商品交易者的重視。公共事業公司也依靠氣溫預報來估計未來的需求。[39][40][41]每日裡,人們參考天氣預報來決定日常的穿戴。因為戶外活動會被大雨、雪以及寒風所嚴重影響,人們依靠預報來計劃活動和為壞天氣做些預先準備。

影響天氣

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]

地球上的極端天氣

斯洛伐克布拉提斯拉瓦清晨的陽光。
同一區域經過小雪在3小時後。

地球上,氣溫的年平均值在±40°C(從100°F至−40°F)的範圍內。整個星球的緯度和氣候的大跨度變化範圍使得有些地方的極端氣溫可能會超出這個範圍。地球上有記錄的最低氣溫是−89.2 °C(−128.6 °F),發生在1983年7月21日南極沃斯托克站。有史以來的最高氣溫是57.7 °C(135.9 °F),發生在1922年9月13日阿齊濟耶省[46],不過這一紀錄被人質疑。最高的年平均氣溫是34.4 °C(93.9 °F),發生在衣索比亞的達洛爾[47]最低的年平均氣溫是−55.1 °C(−67.2 °F),發生在南極沃斯托克站[48]在人類定居區的最低年平均氣溫發生在加拿大境內努納武特地區的尤里卡英語Eureka, Nunavut,達到−19.7 °C(−3.5 °F)。[49]

太陽系內其他星球上的天氣

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]

太空天氣

北極光

天氣不僅僅發生在行星上。和所有恆星一樣,太陽的日冕持續的損耗在太空中,並在整個太陽系產生了一個非常稀薄的大氣。太陽噴射出的物質的移動被稱為太陽風。太陽表面的大型活動(例如日冕物質拋射)以及太陽風的發生反覆無常,使得產生了一個特性與常規天氣系統(例如氣壓和風)相似的系統,常常被稱為太空天氣。太陽系中日冕物質拋射的範圍已經被觀察到可以遠至土星[60]太空天氣也可能會影響到行星大氣,有時還會到星球表面。太陽風和地球大氣的相互作用可以產生壯觀的極光[61]也可能對電敏感系統(如輸電系統和無線電信號)產生重大損害。[62]

參見

參考資料

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外部連結


Category:天氣

基礎條目(30KB或以上)天氣(46705) zh:天氣 en:Weather