用戶:Towerman/translation/雲
氣象學上，雲是行星表面大氣層中由水或多種化學物質構成的可見的液滴或冰晶的集合體。[1]這些懸浮的顆粒物也被稱作氣溶膠，被氣象學的分支雲物理學所研究。
地球上的雲的形成是地球大氣中的空氣因兩種過程而飽和的結果：空氣的冷卻和水汽的增加。當飽和度足夠，降水將形成並下落到地表；幡狀雲是個例外，降水在到達地表前就被蒸發了。[2]
In Earth's atmosphere, the international cloud classification system is based on the fact that these aerosols in their most basic forms can show free-convective upward growth into heaps of cumulus, appear in non-convective layered sheets such as stratus, or take the form of thin fibrous wisps of cirrus. Prefixes are used whenever necessary to express variations or complexities in these basic forms or to specify middle or high altitude ranges. These include strato- for low cumulus layers with limited convection that show some stratus-like characteristics, cumulo- for complex highly-convective storm clouds, nimbo- for thick layers of some complexity that can produce moderate to heavy precipitation, alto- for middle, and cirro- for high clouds. Cloud types prefixed by altitude range may be of simple or moderately complex structure. Whether or not a cloud is low, middle, or high level depends on the altitude range of its base above Earth's surface. Layers or heaps with significant vertical extent can form in the low or middle altitude ranges depending on the moisture content of the air.
Clouds in the troposphere, the atmospheric layer closest to Earth's surface, have Latin names due to the universal adaptation of Luke Howard's nomenclature. It was introduced in December 1802 and became the basis of the modern classification system. Synoptic surface weather observations use code numbers to record and report any type of tropospheric cloud visible at scheduled observation times based on its height and physical appearance.
While a majority of clouds form in Earth's troposphere, there are occasions when they can be observed in the stratosphere and mesosphere. These three main atmospheric layers are collectively known as the homosphere. Above this lies the thermosphere and exosphere, which together make up the heterosphere that marks the transition to outer space. Clouds have been observed on other planets and moons within the Solar System, but, due to their different temperature characteristics, they are composed of other substances such as methane, ammonia, and sulfuric acid.
對氣候的影響
雲在天氣和氣候中的角色是預測全球變暖時的主要不確定性之一。[3]和雲有關的過程的脆弱的平衡，以及從毫米到行星的大範圍的尺度跨度會造成這種不確定性。因此，全球氣候模式很難準確描述大尺度天氣和雲之間的相互作用。前面章節列出的雲的複雜性和多樣性增加了模擬的難度。一方面，白雲頂部對來自太陽的短波輻射會有反射，從而使得地表冷卻。另一方面，大多數到達地面的陽光被地面吸收，加熱了地表，地表又會向上發射長波的紅外的輻射。但是雲中的水對長波輻射是有效的吸收劑。雲又接着會向上和向下發射紅外輻射，向下的輻射會導致地表的淨加熱效果。這個過程和溫室氣體和水汽的溫室效應類似。
高層的對流層雲（例如捲雲）的二重效應（短波反射造成的冷卻和長波溫室升溫效應）會隨着雲量的增加而相互抵消或是產生微小的淨加熱效果。這種短波反射效應在中層雲和低層雲（例如高積雲和層積雲）中佔了主要部分，從而造成幾乎沒有長波效應和淨的冷卻效果。很多研究已經開始關注低層雲對變化的氣候的相應。不同的最先進的全球氣候模式對雲的模擬可能會產生相當不同的結果，有些顯示增加的低層雲，有些則得到低層雲的減少。[4][5]
極地平流層雲和中層雲不太常見，它們的分佈不夠對氣候產生重要的影響。但是，夜光雲出現頻率自19世紀以來逐漸增加可能是氣候變化的結果。[6]
全球亮化
最近的研究顯示了全球亮化的趨勢。[7]雖然造成這一趨勢的原因還沒有能被完全理解，但全球黯化（和後來的逆轉）被認為是由大氣中氣溶膠（特別是生物質燃燒和城市污染帶來的含硫氣溶膠）含量的變化所引起的。[8]氣溶膠含量的變化還可能通過改變雲滴的尺寸分佈[9]或是雲的降水特性和壽命[10]而產生對雲的間接效應。
地外行星
在太陽系中，任何有大氣層的行星或衛星都會有雲。金星的厚厚雲層是由二氧化硫構成的。火星有很高很薄的水冰雲。木星和土星都有一個外層的由氨氣雲構成的雲蓋，中間層是硫化銨雲蓋，裏層是水雲蓋。[11][12]土星的衛星土衛六上的雲被認為主要是由甲烷構成。[13]卡西尼－惠更斯號的土星任務發現了土衛六上存在着液體循環的證據，比如極地附近的湖泊和星球表面的河流沖刷成的溝槽。天王星和海王星的多雲的大氣中主要是水汽和甲烷構成。[14][15]
參考文獻
- ^ Weather Terms. erh. [21 June 2013].
- ^ Weather terms. erh. [21 June 2013].
- ^ D. Randall, R. Wood, S. Bony, R. Colman, T. Fichefet, J. Fyfe, V. Kattsov, A. Pitman, J. Shukla, J. Srinivasan, R. Stouffer, A. Sumi, and K. Taylor (2007) "Climate models and their evaluation" in S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. Averyt, M.Tignor, and H. Miller (eds.) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
- ^ S. Bony and J.-L. Dufresne. Marine boundary layer clouds at the heart of tropical cloud feedback uncertainties in climate models (PDF). Geophysical Research Letters. 2005, 32 (20). doi:10.1029/2005GL023851.
- ^ B. Medeiros, B. Stevens, I.M. Held, M. Zhao, D.L. Williamson, J.G. Olson, and C.S. Bretherton. Aquaplanets, Climate Sensitivity, and Low Clouds. Journal of Climate. 2008, 21 (19): 4974. doi:10.1175/2008JCLI1995.1.
- ^ Kenneth Chang. Caltech Scientist Proposes Explanation for Puzzling Property of Night-Shining Clouds at the Edge of Space. 2008-09-25 [2012-03-13].
- ^ Martin Wild, Hans Gilgen, Andreas Roesch, Atsumu Ohmura, Charles N. Long, Ellsworth G. Dutton, Bruce Forgan, Ain Kallis, Viivi Russak, and Anatoly Tsvetkov. From Dimming to Brightening: Decadal Changes in Solar Radiation at Earth's Surface. Science. 2005, 308 (5723): 847–50. PMID 15879214. doi:10.1126/science.1103215.
- ^ Costantino, L. and F.-M. Bréon. Analysis of aerosol-cloud interaction from multi-sensor satellite observations. Geophysical Research Letters. 2010, 37 (11): n/a. doi:10.1029/2009GL041828.
- ^ S. A. Twomey. Pollution and the planetary albedo. Atmospheric Environment (1967). 1974, 8 (12): 1251. doi:10.1016/0004-6981(74)90004-3.
- ^ B. Stevens and G. Feingold. Untangling aerosol effects on clouds and precipitation in a buffered system. Nature. 2009, 461 (7264): 607–13. PMID 19794487. doi:10.1038/nature08281.
- ^ A.P. Ingersoll, T.E. Dowling, P.J. Gierasch, G.S. Orton, P.L. Read, A. Sanchez-Lavega, A.P. Showman, A.A. Simon-Miller, A.R. Vasavada. Dynamics of Jupiter’s Atmosphere (PDF). Lunar & Planetary Institute. [2007-02-01].
- ^ Monterrey Institute for Research in Astronomy. Saturn. 2006-08-11 [2011-01-31].
- ^ Athéna Coustenis and F.W. Taylor. Titan: Exploring an Earthlike World. World Scientific. 2008: 154–155. ISBN 978-981-270-501-3.
- ^ Jonathan I. Lunine. The Atmospheres of Uranus and Neptune. Annual Review of Astronomy and Astrophysics. 1993-09, 31 (1): 217–263 [2019-06-25]. ISSN 0066-4146. doi:10.1146/annurev.aa.31.090193.001245 （英語）.
- ^ Linda T. Elkins-Tanton. Uranus, Neptune, Pluto, and the Outer Solar System. New York: Chelsea House. 2006: 79–83. ISBN 0-8160-5197-6.
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