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维基百科，自由的百科全书
地球的气候主要由地球能量收支决定。例如的进入和放出辐射量的平衡。辐射量由卫星测量，单位为 W/m2.[1]

地球能量收支或全球能量收支预算（英语：Earth's energy budget）指的是入射大气系统的来自太阳的能量减去散失到外层空间的能量后留在地球和地球大气层中的能量。[2]对于地球能量收支变化的的量化测量值准确地和全球变暖相联系。[3]

2012年1月26-27日大气顶入射太阳短波辐射，表示了从太阳得到的能量。
2012年1月26-27日大气顶地球的长波辐射，表示地球散发的能量。

由于赤道接收的来自太阳的能量较两极多，入射太阳短波辐射在地球不均匀地分布。入射能量被大气圈和水圈吸收，通过地表水的蒸发、对流、降水、风和洋流进一步分布。当入射的太阳辐射与散发到外层空间的能量相同时，地球属于辐射平衡，全球气温相对稳定。

当例如温室气体增加时，地球辐射平衡被改变，全球气温也会改变。[4]然而，地球能量平衡和热量的变动收许多因素影响，例如大气层中化学各物质的占比（主要有气溶胶、温室气体的占比）、地表物体的反照率、云量、植被和土地利用方式。地球表面温度的改变并不是紧随着地球能量收支的变化而变化，由于海洋和冰雪圈对于新能量收支反应的滞后性。净热通量变化在入射和离开地球能量的新平衡状态达到导致气候变化前最主要受到了海洋热含量（英语：Ocean_heat_content）的缓冲。[5]

能量收支[编辑]

入射辐射能量[编辑]

入射辐射能量指大气顶（英语：Top of atmosphere (TOA)）每秒入射能量，以瓦特作为计量单位，是太阳常数和地球横截面积的乘积。由于球体表面积是球体横截面积的4倍，所以大气顶入射能量通量为是太阳常数的四分之一，约为340 W/m²。[1][6]由于入射能量在各地吸收程度的不同和数据的日变化、季节变化和周年变化，使用的数据通常为多个卫星长期检测的平均值。[1]

全球平均每340 W/m²的入射短波辐射有75 W/m²被云层反射回外层空间，30 W/m²被地表反照反射，大约235 W/m²被地球吸收。[7]

地球内部热量和其他小影响[编辑]

来自地球的地热能量约为47兆瓦（47,000,000,000,000瓦）。[8]平均为0.087 W/m²，只占地球表面总能量收支的0.027%，相对于主要的入射太阳辐射（约173,000兆瓦（173x1015瓦））十分微小。[9]

另外也有其他微小的能量来源会影响地球能量收支，但由于数值过于微小而通常忽略不计。例如星际物质的堆积、来自其他行星的光和太空热辐射。虽然这些辐射经常被忽略不计，但是约瑟夫·傅里叶认为这些辐射对于地球能量收支存在一定影响，同时在他的论文中常将其引用为温室效应的诱因之一。[10]

地球长波辐射[编辑]

主条目：地球长波辐射

地球长波辐射指的是地球到外层空间的低能量辐射红外线。当长波辐射离开地球表面后，会先受到大气层的吸收和云层的反射，其余的热量将传导到外层空间。

地球能量不平衡[编辑]

当入射能量和散失的热辐射不相等时，地球能量不平衡将会产生，导致净热通量增加或减少。由Argo计划提供的地球能量不平衡数据测量了近十年的累计海洋热含量。在2005至2010年间的太阳极小期，不平衡量的估算值被测量得0.58 ± 0.15 W/m²。[11]而更新得研究估算这个数据已经增长至0.60 ± 0.17 W/m²。[12]

为了研究地球能量不平衡，一些卫星也被发射到了地球轨道用以间接测量地球吸收和散失的能量，从而推断出地球能量不平衡，这些卫星包括来自美国国家航空航天局的地球辐射收支实验（英语：Radiation Budget Experiment (ERBE)）的卫星。[13]

美国国家航空航天局地球观测系统（英语：Earth Observing System (EOS)）的云和地球辐射能量系统（英语：Clouds and Earth's Radiant Energy System (CERES)）的卫星专门设计为测量大气顶到地面的太阳反射辐射和地球放出辐射而设计。[14]

自然温室效应[编辑]

refer to caption and image description
Diagram showing the energy budget of Earth's atmosphere, which includes the greenhouse effect

The major atmospheric gases (oxygen and nitrogen) are transparent to incoming sunlight, and are also transparent to outgoing thermal infrared. However, water vapor, carbon dioxide, methane, and other trace gases are opaque to many wavelengths of thermal infrared energy. The Earth's surface radiates the net equivalent of 17 percent of incoming solar energy as thermal infrared. However, the amount that directly escapes to space is only about 12 percent of incoming solar energy. The remaining fraction—a net 5-6 percent of incoming solar energy—is transferred to the atmosphere when greenhouse gas molecules absorb thermal infrared energy radiated by the surface.[15]

Atmospheric gases only absorb some wavelengths of energy but are transparent to others. The absorption patterns of water vapor (blue peaks) and carbon dioxide (pink peaks) overlap in some wavelengths. Carbon dioxide is not as strong a greenhouse gas as water vapor, but it absorbs energy in wavelengths (12–15 micrometres) that water vapor does not, partially closing the "window" through which heat radiated by the surface would normally escape to space. (Illustration NASA, Robert Rohde)[16]

When greenhouse gas molecules absorb thermal infrared energy, their temperature rises. Like coals from a fire that are warm but not glowing, greenhouse gases then radiate an increased amount of thermal infrared energy in all directions. Heat radiated upward continues to encounter greenhouse gas molecules; those molecules absorb the heat, their temperature rises, and the amount of heat they radiate increases. At an altitude of roughly 5–6 kilometres, the concentration of greenhouse gases in the overlying atmosphere is so small that heat can radiate freely to space.[15]

Because greenhouse gas molecules radiate infrared energy in all directions, some of it spreads downward and ultimately comes back into contact with the Earth's surface, where it is absorbed. The temperature of the surface becomes warmer than it would be if it were heated only by direct solar heating. This supplemental heating of the Earth's surface by the atmosphere is the natural greenhouse effect.[15]

气候敏感度[编辑]

A change in the incident or radiated portion of the energy budget is referred to as a radiative forcing.

The climate sensitivity is defined as the steady state change in the equilibrium temperature as a result of changes in the energy budget.

气候因子和全球变暖[编辑]

Expected Earth energy imbalance for three choices of aerosol climate forcing. Measured imbalance, close to 0.6 W/m², implies that aerosol forcing is close to −1.6 W/m². (Credit: NASA/GISS)[11]

Changes in Earth's climate system that affect the energy which enters or leaves the system alters Earth's radiative equilibrium, and thus can force temperatures to rise or fall, are called climate forcings. Natural climate forcings include changes in the Sun's brightness, Milankovitch cycles (small variations in the shape of Earth's orbit and its axis of rotation that occur over thousands of years), and large volcanic eruptions that inject light-reflecting particles as high as the stratosphere. Man-made forcings include particle pollution (aerosols), which absorb and reflect incoming sunlight; deforestation, which changes how the surface reflects and absorbs sunlight; and the rising concentration of atmospheric carbon dioxide and other greenhouse gases, which decrease heat radiated to space.

A forcing can trigger feedbacks that intensify (positive feedback) or weaken (negative feedback) the original forcing. For example, loss of ice at the poles, which makes them less reflective, is an example of a positive feedback.[16]

The observed planetary energy imbalance during the recent solar minimum shows that solar forcing of climate, although significant, is overwhelmed by a much larger net human-made climate forcing.

Today, anthropogenic perturbations in greenhouse gas concentration are responsible for a positive radiative forcing which reduces the net longwave radiation loss out to space, hence the radiative equilibrium is disturbed. It has been suggested to reduce atmospheric CO2 content to about 350 ppm, in order to stop further global warming. The data also show that climate forcing by human-made aerosols is larger than usually assumed, hence more global aerosol monitoring would improve people's understanding of interpretation of recent climate change.[11]

参看[编辑]

参考资料[编辑]

  1. ^ 1.0 1.1 1.2 The NASA Earth's Energy Budget Poster. NASA. 
  2. ^ IPCC AR5 WG1 Glossary 2013 "energy budget (of the earth)"
  3. ^ Graeme L. Stephens, Juilin Li, Martin Wild, Carol Anne Clayson, Norman Loeb, Seiji Kato, Tristan L'Ecuyer, Paul W. Stackhouse Jr, Matthew Lebsock and Timothy Andrews. An update on Earth's energy balance in light of the latest global observations (PDF). Nature Geoscience. September 23, 2012. Bibcode:2012NatGe...5..691S. doi:10.1038/NGEO1580. 
  4. ^ Lindsey, Rebecca. Climate and Earth's Energy Budget. NASA Earth Observatory. 2009. 
  5. ^ M, Previdi; et al. Climate sensitivity in the Anthropocene. Royal Meteorological Society. 2013. Bibcode:2013QJRMS.139.1121P. doi:10.1002/qj.2165. 
  6. ^ Wild, Martin; Folini, Doris; Schär, Christoph; Loeb, Norman; Dutton, Ellsworth; König-Langlo, Gert. The Earth's radiation balance and its representation in CMIP5 models. Copernicus. 2013. Bibcode:2013EGUGA..15.1286W. 
  7. ^ Kevin E. Trenberth, John T. Fasullo, Jeffrey Kiehl. 周跃武，白虎志 译. 全球能量收支预算 (PDF). 干旱气象. 2010, (2010年6月第28卷第2期). 
  8. ^ Davies, J. H., & Davies, D. R. (2010).
  9. ^ Archer, D. Global Warming: Understanding the Forecast. 2012. ISBN 978-0-470-94341-0. 
  10. ^ Connolley, William M. William M. Connolley's page about Fourier 1827: MEMOIRE sur les temperatures du globe terrestre et des espaces planetaires. William M. Connolley. 18 May 2003 [5 July 2010]. 
  11. ^ 11.0 11.1 11.2 James Hansen, Makiko Sato, Pushker Kharecha and Karina von Schuckmann. Earth's Energy Imbalance. NASA. January 2012. 
  12. ^ http://www.nature.com/ngeo/journal/v5/n10/full/ngeo1580.html
  13. ^ Effect of the Sun's Energy on the Ocean and Atmosphere (1997)
  14. ^ B.A. Wielicki; et al. Mission to Planet Earth: Role of Clouds and Radiation in Climate. Bull. Amer. Meteorol. Soc. 1996, 77 (5): 853–868. Bibcode:1996BAMS...77..853W. doi:10.1175/1520-0477(1996)077<0853:CATERE>2.0.CO;2. 
  15. ^ 15.0 15.1 15.2 Edited quote from public-domain source: Lindsey, R., The Atmosphere's Energy Budget (page 6), in: Climate and Earth's Energy Budget: Feature Articles, Earth Observatory, part of the EOS Project Science Office, located at NASA Goddard Space Flight Center, January 14, 2009 
  16. ^ 16.0 16.1 NASA: Climate Forcings and Global Warming. January 14, 2009. 

外部链接[编辑]

Category:气候因子 Category:地球 Category:地球科学 Category:能量

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