Science Unit 3 Vocab

greenhouse effect

Banner logo This November is the Wikipedia Asian Month. Come join us. Hide Page semi-protected Greenhouse effect From Wikipedia, the free encyclopedia For other uses, see Greenhouse (disambiguation). A representation of the exchanges of energy between the source (the Sun), Earth's surface, the Earth's atmosphere, and the ultimate sink outer space. The ability of the atmosphere to capture and recycle energy emitted by Earth's surface is the defining characteristic of the greenhouse effect. Energy flow between the sun, the atmosphere and earth's surface. Earth's energy budget The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere.[1][2] If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) they will radiate energy in all directions. Part of this radiation is directed towards the surface, warming it.[3] The intensity of the downward radiation - that is, the strength of the greenhouse effect - will depend on the atmosphere's temperature and on the amount of greenhouse gases that the atmosphere contains. Earth's natural greenhouse effect is critical to supporting life. Human activities, primarily the burning of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causing global warming.[4] The mechanism is named after a faulty analogy with the effect of solar radiation passing through glass and warming a greenhouse. The way a greenhouse retains heat is fundamentally different, as a greenhouse works mostly by reducing airflow and thus retaining warm air inside the structure.[2][5][6] Contents [hide] 1 History 2 Mechanism 3 Greenhouse gases 4 Role in climate change 5 Real greenhouses 6 Related effects 6.1 Anti-greenhouse effect 6.2 Runaway greenhouse effect 7 Bodies other than Earth 8 See also 9 References 10 Further reading 11 External links History Main article: History of climate change science The existence of the greenhouse effect was argued for by Joseph Fourier in 1824. The argument and the evidence were further strengthened by Claude Pouillet in 1827 and 1838 and reasoned from experimental observations by John Tyndall in 1859, who measured the radiative properties of specific greenhouse gases.[7] The effect was more fully quantified by Svante Arrhenius in 1896, who made the first quantitative prediction of global warming due to a hypothetical doubling of atmospheric carbon dioxide.[8] However, the term "greenhouse" was not used to refer to this effect by any of these scientists; the term was first used in this way by Nils Gustaf Ekholm in 1901.[9][10] Mechanism Earth receives energy from the Sun in the form of ultraviolet, visible, and near-infrared radiation. Of the total amount of solar energy available at the top of the atmosphere, about 26% is reflected to space by the atmosphere and clouds and 19% is absorbed by the atmosphere and clouds. Most of the remaining energy is absorbed at the surface of Earth. Because the Earth's surface is colder than the photosphere of the Sun, it radiates at wavelengths that are much longer than the wavelengths that were absorbed. Most of this thermal radiation is absorbed by the atmosphere, thereby warming it. In addition to the absorption of solar and thermal radiation, the atmosphere gains heat by sensible and latent heat fluxes from the surface. The atmosphere radiates energy both upwards and downwards; the part radiated downwards is absorbed by the surface of Earth. This leads to a higher equilibrium temperature than if the atmosphere were absent. The solar radiation spectrum for direct light at both the top of Earth's atmosphere and at sea level An ideal thermally conductive blackbody at the same distance from the Sun as Earth would have a temperature of about 5.3 °C. However, because Earth reflects about 30%[11][12] of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C.[13][14] The surface temperature of this hypothetical planet is 33 °C below Earth's actual surface temperature of approximately 14 °C.[15] The basic mechanism can be qualified in a number of ways, none of which affect the fundamental process. The atmosphere near the surface is largely opaque to thermal radiation (with important exceptions for "window" bands), and most heat loss from the surface is by sensible heat and latent heat transport. Radiative energy losses become increasingly important higher in the atmosphere, largely because of the decreasing concentration of water vapor, an important greenhouse gas. It is more realistic to think of the greenhouse effect as applying to a "surface" in the mid-troposphere, which is effectively coupled to the surface by a lapse rate. The simple picture also assumes a steady state, but in the real world, there are variations due to the diurnal cycle as well as the seasonal cycle and weather disturbances. Solar heating only applies during daytime. During the night, the atmosphere cools somewhat, but not greatly, because its emissivity is low. Diurnal temperature changes decrease with height in the atmosphere. Within the region where radiative effects are important, the description given by the idealized greenhouse model becomes realistic. Earth's surface, warmed to a temperature around 255 K, radiates long-wavelength, infrared heat in the range of 4-100 μm.[16] At these wavelengths, greenhouse gases that were largely transparent to incoming solar radiation are more absorbent.[16] Each layer of atmosphere with greenhouses gases absorbs some of the heat being radiated upwards from lower layers. It reradiates in all directions, both upwards and downwards; in equilibrium (by definition) the same amount as it has absorbed. This results in more warmth below. Increasing the concentration of the gases increases the amount of absorption and reradiation, and thereby further warms the layers and ultimately the surface below.[14] Greenhouse gases—including most diatomic gases with two different atoms (such as carbon monoxide, CO) and all gases with three or more atoms—are able to absorb and emit infrared radiation. Though more than 99% of the dry atmosphere is IR transparent (because the main constituents—N2, O2, and Ar—are not able to directly absorb or emit infrared radiation), intermolecular collisions cause the energy absorbed and emitted by the greenhouse gases to be shared with the other, non-IR-active, gases. Greenhouse gases Main article: Greenhouse gas By their percentage contribution to the greenhouse effect on Earth the four major gases are:[17][18] 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 longer wavelengths (12-15 micrometers) 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)[19] water vapor, 36-70% carbon dioxide, 9-26% methane, 4-9% ozone, 3-7% It is not physically realistic to assign a specific percentage to each gas because the absorption and emission bands of the gases overlap (hence the ranges given above). The major non-gas contributor to Earth's greenhouse effect, clouds, also absorb and emit infrared radiation and thus have an effect on the radiative properties of the atmosphere.[18] Role in climate change Main article: Global warming The Keeling Curve of atmospheric CO2 concentrations measured at Mauna Loa Observatory. Strengthening of the greenhouse effect through human activities is known as the enhanced (or anthropogenic) greenhouse effect.[20] This increase in radiative forcing from human activity is attributable mainly to increased atmospheric carbon dioxide levels.[21] According to the latest Assessment Report from the Intergovernmental Panel on Climate Change, "atmospheric concentrations of carbon dioxide, methane and nitrous oxide are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century".[22] CO2 is produced by fossil fuel burning and other activities such as cement production and tropical deforestation.[23] Measurements of CO2 from the Mauna Loa observatory show that concentrations have increased from about 313 parts per million (ppm)[24] in 1960 to about 389 ppm in 2010. It reached the 400 ppm milestone on May 9, 2013.[25] The current observed amount of CO2 exceeds the geological record maxima (~300 ppm) from ice core data.[26] The effect of combustion-produced carbon dioxide on the global climate, a special case of the greenhouse effect first described in 1896 by Svante Arrhenius, has also been called the Callendar effect. Over the past 800,000 years,[27] ice core data shows that carbon dioxide has varied from values as low as 180 ppm to the pre-industrial level of 270 ppm.[28] Paleoclimatologists consider variations in carbon dioxide concentration to be a fundamental factor influencing climate variations over this time scale.[29][30] Real greenhouses A modern Greenhouse in RHS Wisley The "greenhouse effect" of the atmosphere is named by analogy to greenhouses which become warmer in sunlight. However, a greenhouse is not primarily warmed by the "greenhouse effect".[31] "Greenhouse effect" is actually a misnomer since heating in the usual greenhouse is due to the reduction of convection,[32] while the "greenhouse effect" works by preventing absorbed heat from leaving the structure through radiative transfer. A greenhouse is built of any material that passes sunlight usually glass, or plastic. The sun warms the ground and contents inside just like the outside, which then warms the air. Outside, the warm air near the surface rises and mixes with cooler air aloft, keeping the temperature lower than inside, where the air continues to heat up because it is confined within the greenhouse. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature will drop considerably. It was demonstrated experimentally (R. W. Wood, 1909) that a (not heated) "greenhouse" with a cover of rock salt (which is transparent to infrared) heats up an enclosure similarly to one with a glass cover.[6] Thus greenhouses work primarily by preventing convective cooling.[5] Heated greenhouses are yet another matter, having an internal source of heating they leak heat out, which must be prevented. So it again makes sense to try to prevent radiative cooling through the use of adequate glazing.[33] Related effects Anti-greenhouse effect See also: Anti-greenhouse effect The anti-greenhouse effect is a mechanism similar and symmetrical to the greenhouse effect: greenhouse effect is about atmosphere letting radiation in, while not letting thermal radiation out, which warms the body surface; anti-greenhouse effect is about atmosphere NOT letting radiation in, while letting thermal radiation out, which lowers the equilibrium surface temperature. Such an effect has been cited about Titan[34] Runaway greenhouse effect See also: runaway greenhouse effect A runaway greenhouse effect occurs if positive feedbacks lead to the evaporation of all greenhouse gases into the atmosphere.[35] A runaway greenhouse effect involving carbon dioxide and water vapor has long ago been hypothesized to have occurred on Venus,[36] this idea is still largely accepted[citation needed]. Bodies other than Earth The greenhouse effect on Venus is particularly large because its dense atmosphere consists mainly of carbon dioxide.[37] Titan has an anti-greenhouse effect, in that its atmosphere absorbs solar radiation but is relatively transparent to outgoing infrared radiation. Pluto is also colder than would be expected because evaporation of nitrogen cools it.[38] See also icon Global warming portal icon Environment portal Earth's energy budget References Jump up ^ "Annex II Glossary". Intergovernmental Panel on Climate Change. Retrieved 15 October 2010. ^ Jump up to: a b A concise description of the greenhouse effect is given in the Intergovernmental Panel on Climate Change Fourth Assessment Report, "What is the Greenhouse Effect?" FAQ 1.3 - AR4 WGI Chapter 1: Historical Overview of Climate Change Science, IIPCC Fourth Assessment Report, Chapter 1, page 115: "To balance the absorbed incoming [solar] energy, the Earth must, on average, radiate the same amount of energy back to space. Because the Earth is much colder than the Sun, it radiates at much longer wavelengths, primarily in the infrared part of the spectrum (see Figure 1). Much of this thermal radiation emitted by the land and ocean is absorbed by the atmosphere, including clouds, and reradiated back to Earth. This is called the greenhouse effect." Stephen H. Schneider, in Geosphere-biosphere Interactions and Climate, Lennart O. Bengtsson and Claus U. Hammer, eds., Cambridge University Press, 2001, ISBN 0-521-78238-4, pp. 90-91. E. Claussen, V. A. Cochran, and D. P. Davis, Climate Change: Science, Strategies, & Solutions, University of Michigan, 2001. p. 373. A. Allaby and M. Allaby, A Dictionary of Earth Sciences, Oxford University Press, 1999, ISBN 0-19-280079-5, p. 244. Jump up ^ Vaclav Smil (2003). The Earth's Biosphere: Evolution, Dynamics, and Change. MIT Press. p. 107. ISBN 978-0-262-69298-4. Jump up ^ IPCC AR4 WG1 (2007), Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K.B.; Tignor, M.; Miller, H.L., 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, ISBN 978-0-521-88009-1 (pb: 978-0-521-70596-7) ^ Jump up to: a b Schroeder, Daniel V. (2000). An introduction to thermal physics. San Francisco, California: Addison-Wesley. pp. 305-7. ISBN 0-321-27779-1. ... this mechanism is called the greenhouse effect, even though most greenhouses depend primarily on a different mechanism (namely, limiting convective cooling). ^ Jump up to: a b Wood, R.W. (1909). "Note on the Theory of the Greenhouse". Philosophical Magazine. 17: 319-320. doi:10.1080/14786440208636602. When exposed to sunlight the temperature rose gradually to 65 °C., the enclosure covered with the salt plate keeping a little ahead of the other because it transmitted the longer waves from the Sun, which were stopped by the glass. In order to eliminate this action the sunlight was first passed through a glass plate." "it is clear that the rock-salt plate is capable of transmitting practically all of it, while the glass plate stops it entirely. This shows us that the loss of temperature of the ground by radiation is very small in comparison to the loss by convection, in other words that we gain very little from the circumstance that the radiation is trapped. Jump up ^ John Tyndall, Heat considered as a Mode of Motion (500 pages; year 1863, 1873) Jump up ^ Isaac M. Held; Brian J. Soden (Nov 2000). "Water Vapor Feedback and Global Warming". Annual Review of Energy and the Environment. Annual Reviews. 25: 441-475. doi:10.1146/annurev.energy.25.1.441. Jump up ^ Easterbrook, Steve. "Who first coined the term "Greenhouse Effect"?". Serendipity. Retrieved 11 November 2015. Jump up ^ Ekholm N (1901). "On The Variations Of The Climate Of The Geological And Historical Past And Their Causes". Quarterly Journal of the Royal Meteorological Society. 27 (117): 1-62. Bibcode:1901QJRMS..27....1E. doi:10.1002/qj.49702711702. Jump up ^ "NASA Earth Fact Sheet". Nssdc.gsfc.nasa.gov. Retrieved 2010-10-15. Jump up ^ "Introduction to Atmospheric Chemistry, by Daniel J. Jacob, Princeton University Press, 1999. Chapter 7, "The Greenhouse Effect"". Acmg.seas.harvard.edu. Retrieved 2010-10-15. Jump up ^ "Solar Radiation and the Earth's Energy Balance". Eesc.columbia.edu. Retrieved 2010-10-15. ^ Jump up to: a b Intergovernmental Panel on Climate Change Fourth Assessment Report. Chapter 1: Historical overview of climate change science page 97 Jump up ^ The elusive "absolute surface air temperature," see GISS discussion ^ Jump up to: a b Mitchell, John F. B. (1989). "THE "GREENHOUSE" EFFECT AND CLIMATE CHANGE" (PDF). Reviews of Geophysics. American Geophysical Union. 27 (1): 115-139. Bibcode:1989RvGeo..27..115M. doi:10.1029/RG027i001p00115. Retrieved 2008-03-23. Jump up ^ "Water vapour: feedback or forcing?". RealClimate. 6 April 2005. Retrieved 2006-05-01. ^ Jump up to: a b Kiehl, J. T.; Kevin E. Trenberth (February 1997). "Earth's Annual Global Mean Energy Budget" (PDF). Bulletin of the American Meteorological Society. 78 (2): 197-208. Bibcode:1997BAMS...78..197K. doi:10.1175/1520-0477(1997)078<0197:EAGMEB>2.0.CO;2. ISSN 1520-0477. Archived from the original (PDF) on 2006-03-30. Retrieved 2006-05-01. Jump up ^ "NASA: Climate Forcings and Global Warming". January 14, 2009. Jump up ^ "Enhanced greenhouse effect — Glossary". Nova. Australian Academy of Scihuman impact on the environment. 2006. Jump up ^ "Enhanced Greenhouse Effect". Ace.mmu.ac.uk. Archived from the original on 2010-10-24. Retrieved 2010-10-15. Jump up ^ IPCC Fifth Assessment Report Synthesis Report: Summary for Policymakers (p. 4) Jump up ^ IPCC Fourth Assessment Report, Working Group I Report "The Physical Science Basis" Chapter 7 Jump up ^ "Atmospheric Carbon Dioxide - Mauna Loa". NOAA. Jump up ^ http://news.nationalgeographic.com/news/energy/2013/05/130510-earth-co2-milestone-400-ppm/ Jump up ^ Hansen J. (February 2005). "A slippery slope: How much global warming constitutes "dangerous anthropogenic interference"?". Climatic Change. 68 (333): 269-279. doi:10.1007/s10584-005-4135-0. Jump up ^ "Deep ice tells long climate story". BBC News. 2006-09-04. Retrieved 2010-05-04. Jump up ^ Hileman B (2005-11-28). "Ice Core Record Extended". Chemical & Engineering News. 83 (48): 7. Jump up ^ Bowen, Mark; Thin Ice: Unlocking the Secrets of Climate in the World's Highest Mountains; Owl Books, 2005. Jump up ^ Temperature change and carbon dioxide change, U.S. National Oceanic and Atmospheric Administration Jump up ^ Brian Shmaefsky (2004). Favorite demonstrations for college science: an NSTA Press journals collection. NSTA Press. p. 57. ISBN 978-0-87355-242-4. Jump up ^ Oort, Abraham H.; Peixoto, José Pinto (1992). Physics of climate. New York: American Institute of Physics. ISBN 0-88318-711-6. ...the name water vapor-greenhouse effect is actually a misnomer since heating in the usual greenhouse is due to the reduction of convection Jump up ^ > ENERGY EFFECTS DURING USING THE GLASS WITH DIFFERENT PROPERTIES IN A HEATED GREENHOUSE, Sławomir Kurpaska, Technical Sciences 17(4), 2014, 351-360 Jump up ^ "Titan: Greenhouse and Anti-greenhouse :: Astrobiology Magazine - earth science - evolution distribution Origin of life universe - life beyond :: Astrobiology is study of earth". Astrobio.net. Retrieved 2010-10-15. Jump up ^ Kasting, James F. (1991). "Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus.". Planetary Sciences: American and Soviet Research/Proceedings from the U.S.-U.S.S.R. Workshop on Planetary Sciences. Commission on Engineering and Technical Systems (CETS). pp. 234-245. Retrieved 9 April 2017. Jump up ^ Rasool, I.; De Bergh, C. (Jun 1970). "The Runaway Greenhouse and the Accumulation of CO2 in the Venus Atmosphere" (PDF). Nature. 226 (5250): 1037-1039. Bibcode:1970Natur.226.1037R. doi:10.1038/2261037a0. ISSN 0028-0836. PMID 16057644.[permanent dead link] Jump up ^ McKay, C.; Pollack, J.; Courtin, R. (1991). "The greenhouse and antigreenhouse effects on Titan". Science. 253 (5024): 1118-1121. doi:10.1126/science.11538492. PMID 11538492. Jump up ^ "Pluto Colder Than Expected". SPACE.com. 2006-01-03. Retrieved 2010-10-15. Further reading Businger, Joost Alois; Fleagle, Robert Guthrie (1980). An introduction to atmospheric physics. International geophysics series (2nd ed.). San Diego: Academic. ISBN 0-12-260355-9. Henderson-Sellers, Ann; McGuffie, Kendal (2005). A climate modelling primer (3rd ed.). New York: Wiley. ISBN 0-470-85750-1. Schelling, Thomas C. (2002). "Greenhouse Effect". In David R. Henderson (ed.). Concise Encyclopedia of Economics (1st ed.). Library of Economics and Liberty. OCLC 317650570, 50016270, 163149563 External links Find more about Greenhouse effect at Wikipedia's sister projects Definitions from Wiktionary Media from Commons News from Wikinews Textbooks from Wikibooks Learning resources from Wikiversity Data from Wikidata Rutgers University: Earth Radiation Budget [hide] v t e Global warming and climate change [show] Temperatures [hide] Causes Anthropogenic Attribution of recent climate change Aviation Biofuel Black carbon Carbon dioxide Deforestation Earth's energy budget Earth's radiation balance Ecocide Fossil fuel Global dimming Global warming potential Greenhouse effect (Infrared window) Greenhouse gases (Halocarbons) Land use, land-use change and forestry Radiative forcing Tropospheric ozone Urban heat island Natural Albedo Bond events Climate oscillations Climate sensitivity Cloud forcing Cosmic rays Feedbacks Glaciation Global cooling Milankovitch cycles Ocean variability AMO ENSO IOD PDO Orbital forcing Solar variation Volcanism Models Global climate model [show] History [show] Opinion and climate change [show] Politics [show] Potential effects and issues [show] Mitigation [show] Proposed adaptations Glossary of climate change Index of climate change articles Category:Climate change Category:Global warming Portal:Global warming Authority control BNF: cb119830305 (data) NDL: 00576626 Categories: AtmosphereAtmospheric radiationClimate changeClimate forcingClimate forcing agents

troposphere

Main menuHOMETEACHERSSTUDENTSLEARNING ZONEVISIT NCARBLOGABOUT Search form Search Search The Troposphere - overview This diagram shows some of the features of the troposphere. Credit: Randy Russell, UCAR The troposphere is the lowest layer of Earth's atmosphere. Most of the mass (about 75-80%) of the atmosphere is in the troposphere. Most types of clouds are found in the troposphere, and almost all weather occurs within this layer. The bottom of the troposphere is at Earth's surface. The troposphere extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level. The height of the top of the troposphere varies with latitude (it is lowest over the poles and highest at the equator) and by season (it is lower in winter and higher in summer). It can be as high as 20 km (12 miles or 65,000 feet) near the equator, and as low as 7 km (4 miles or 23,000 feet) over the poles in winter. Air is warmest at the bottom of the troposphere near ground level. Air gets colder as one rises through the troposphere. That's why the peaks of tall mountains can be snow-covered even in the summertime. Air pressure and the density of the air also decrease with altitude. That's why the cabins of high-flying jet aircraft are pressurized. The layer immediately above the troposphere is called the stratosphere. The boundary between the troposphere and the stratosphere is called the "tropopause". © 2011 UCAR 36 calendar imageEVENTS AND HIGHLIGHTS SIGN UP FOR K-12 NEWS email address Subscribe MORE ABOUT LAYERS OF THE ATMOSPHERE >Layers of Earth's Atmosphere >Stratosphere >Earth's Atmosphere - overview EXPLORE THE TROPOSPHERE >Virtual Ballooning to Explore the Atmosphere >Clouds Memory Game >Atmospheric Chemistry Memory Game © 2017 UCAR | Privacy Policy | Terms of Use | Copyright Issues | Sponsored by NSF | Managed by UCAR | Webmaster/Feedback Postal Address: P.O. Box 3000, Boulder, CO 80307-3000 • Shipping Address: 3090 Center Green Drive, Boulder, CO 80301 The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

air pressure

This November is the Wikipedia Asian Month. Come join us. Hide Atmospheric pressure From Wikipedia, the free encyclopedia "Air pressure" redirects here. For the pressure of air in other systems, see Pressure. Continuum mechanics Laws[show] Solid mechanics[show] Fluid mechanics[show] Rheology[show] Scientists[show] v t e Atmospheric pressure, sometimes also called barometric pressure, is the pressure within the atmosphere of Earth (or that of another planet). In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. Pressure measures force per unit area, with SI units of pascals (1 Pa = 1 N/m2). On average, a column of air one square centimetre [cm2] (0.16 sq in) in cross-section, measured from sea level to the top of the Earth's atmosphere, has a mass of about 1.03 kilograms (2.3 lb) and weight of about 10.1 newtons (2.3 lbf). That weight (across one square centimeter) is a pressure of 10.1 N/cm2 or 101 kN/m2 (kPa). A column 1 square inch (6.5 cm2) in cross-section would have a weight of about 14.7 lb (6.7 kg) or about 65.4 N. Contents [hide] 1 Mechanism 2 Standard atmosphere 3 Mean sea level pressure 4 Altitude variation 5 Local variation 6 Records 7 Measurement based on depth of water 8 Boiling point of water 9 Measurement and maps 10 See also 11 References 12 External links 12.1 Experiments Mechanism[edit] This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2017) (Learn how and when to remove this template message) Atmospheric pressure is caused by the gravitational attraction of the planet on the atmospheric gases above the surface, and is a function of the mass of the planet, the radius of the surface, and the amount of gas and its vertical distribution in the atmosphere.[citation needed] It is modified by the planetary rotation and local effects such as wind velocity, density variations due to temperature and variations in composition.[citation needed] Standard atmosphere[edit] The standard atmosphere (symbol: atm) is a unit of pressure defined as 101325 Pa (1.01325 bar), equivalent to 760 mmHg (torr), 29.92 inHg and 14.696 psi.[1] Mean sea level pressure[edit] 15 year average mean sea level pressure for June, July, and August (top) and December, January, and February (bottom). ERA-15 re-analysis. Kollsman-type barometric aircraft altimeter (as used in North America) displaying an altitude of 80 ft (24 m). The mean sea level pressure (MSLP) is the average atmospheric pressure at sea level. This is the atmospheric pressure normally given in weather reports on radio, television, and newspapers or on the Internet. When barometers in the home are set to match the local weather reports, they measure pressure adjusted to sea level, not the actual local atmospheric pressure. The altimeter setting in aviation is an atmospheric pressure adjustment. Average sea-level pressure is 1013.25 mbar (101.325 kPa; 29.921 inHg; 760.00 mmHg). In aviation weather reports (METAR), QNH is transmitted around the world in millibars or hectopascals (1 hectopascal = 1 millibar), except in the United States, Canada, and Colombia where it is reported in inches (to two decimal places) of mercury. The United States and Canada also report sea level pressure SLP, which is adjusted to sea level by a different method, in the remarks section, not in the internationally transmitted part of the code, in hectopascals or millibars.[2] However, in Canada's public weather reports, sea level pressure is instead reported in kilopascals.[3] In the US weather code remarks, three digits are all that are transmitted; decimal points and the one or two most significant digits are omitted: 1013.2 mbar (101.32 kPa) is transmitted as 132; 1000.0 mbar (100.00 kPa) is transmitted as 000; 998.7 mbar is transmitted as 987; etc. The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1050 mbar (105 kPa; 31 inHg), with record highs close to 1085 mbar (108.5 kPa; 32.0 inHg). The lowest measurable sea-level pressure is found at the centers of tropical cyclones and tornadoes, with a record low of 870 mbar (87 kPa; 26 inHg) (see Atmospheric pressure records). Altitude variation[edit] A very local storm above Snæfellsjökull, showing clouds formed on the mountain by orographic lift Variation in atmospheric pressure with altitude, computed for 15 °C and 0% relative humidity. This plastic bottle was sealed at approximately 14,000 feet (4,300 m) altitude, and was crushed by the increase in atmospheric pressure —at 9,000 feet (2,700 m) and 1,000 feet (300 m)— as it was brought down towards sea level. Pressure varies smoothly from the Earth's surface to the top of the mesosphere. Although the pressure changes with the weather, NASA has averaged the conditions for all parts of the earth year-round. As altitude increases, atmospheric pressure decreases. One can calculate the atmospheric pressure at a given altitude.[4] Temperature and humidity also affect the atmospheric pressure, and it is necessary to know these to compute an accurate figure. The graph at right was developed for a temperature of 15 °C and a relative humidity of 0%. At low altitudes above sea level, the pressure decreases by about 1.2 kPa for every 100 metres. For higher altitudes within the troposphere, the following equation (the barometric formula) relates atmospheric pressure p to altitude h {\displaystyle p=p_{0}\cdot \left(1-{\frac {L\cdot h}{T_{0}}}\right)^{\frac {g\cdot M}{R_{0}\cdot L}}\approx p_{0}\cdot \left(1-{\frac {g\cdot h}{c_{p}\cdot T_{0}}}\right)^{\frac {c_{p}\cdot M}{R_{0}}},} {\displaystyle p=p_{0}\cdot \left(1-{\frac {L\cdot h}{T_{0}}}\right)^{\frac {g\cdot M}{R_{0}\cdot L}}\approx p_{0}\cdot \left(1-{\frac {g\cdot h}{c_{p}\cdot T_{0}}}\right)^{\frac {c_{p}\cdot M}{R_{0}}},} {\displaystyle p\approx p_{0}\cdot \exp \left(-{\frac {g\cdot M\cdot h}{R_{0}\cdot T_{0}}}\right)} {\displaystyle p\approx p_{0}\cdot \exp \left(-{\frac {g\cdot M\cdot h}{R_{0}\cdot T_{0}}}\right)} where the constant parameters are as described below: Parameter Description Value p0 sea level standard atmospheric pressure 101325 Pa L temperature lapse rate, = g/cp for dry air 0.0065 K/m cp constant pressure specific heat ~ 1007 J/(kg•K) T0 sea level standard temperature 288.15 K g Earth-surface gravitational acceleration 9.80665 m/s2 M molar mass of dry air 0.0289644 kg/mol R0 universal gas constant 8.31447 J/(mol•K) Local variation[edit] Hurricane Wilma on 19 October 2005; 882 hPa (12.79 psi) in the storm's eye Atmospheric pressure varies widely on Earth, and these changes are important in studying weather and climate. See pressure system for the effects of air pressure variations on weather. Atmospheric pressure shows a diurnal or semidiurnal (twice-daily) cycle caused by global atmospheric tides. This effect is strongest in tropical zones, with an amplitude of a few millibars, and almost zero in polar areas. These variations have two superimposed cycles, a circadian (24 h) cycle and semi-circadian (12 h) cycle. Records[edit] The highest adjusted-to-sea level barometric pressure ever recorded on Earth (above 750 meters) was 1085.7 hPa (32.06 inHg) measured in Tosontsengel, Mongolia on 19 December 2001.[5] The highest adjusted-to-sea level barometric pressure ever recorded (below 750 meters) was at Agata in Evenk Autonomous Okrug, Russia (66°53'N, 93°28'E, elevation: 261 m, 856 ft) on 31 December 1968 of 1083.8 hPa (32.005 inHg).[6] The discrimination is due to the problematic assumptions (assuming a standard lapse rate) associated with reduction of sea level from high elevations.[5] The Dead Sea, the lowest place on Earth at 430 metres (1,410 ft) below sea level, has a correspondingly high typical atmospheric pressure of 1065 hPa.[7] The lowest non-tornadic atmospheric pressure ever measured was 870 hPa (0.858 atm; 25.69 inHg), set on 12 October 1979, during Typhoon Tip in the western Pacific Ocean. The measurement was based on an instrumental observation made from a reconnaissance aircraft.[8] Measurement based on depth of water[edit] One atmosphere (101 kPa or 14.7 psi) is also the pressure caused by the weight of a column of fresh water of approximately 10.3 m (33.8 ft). Thus, a diver 10.3 m underwater experiences a pressure of about 2 atmospheres (1 atm of air plus 1 atm of water). Conversely, 10.3 m is the maximum height to which water can be raised using suction under standard atmospheric conditions. Low pressures such as natural gas lines are sometimes specified in inches of water, typically written as w.c. (water column) or w.g. (inches water gauge). A typical gas-using residential appliance in the US is rated for a maximum of 14 w.c., which is approximately 35 hPa. Similar metric units with a wide variety of names and notation based on millimetres, centimetres or metres are now less commonly used. Boiling point of water[edit] Boiling water Pure water boils at 100 °C (212 °F) at earth's standard atmospheric pressure. The boiling point is the temperature at which the vapor pressure is equal to the atmospheric pressure around the water.[9] Because of this, the boiling point of water is lower at lower pressure and higher at higher pressure. Cooking at high elevations, therefore, requires adjustments to recipes.[10] A rough approximation of elevation can be obtained by measuring the temperature at which water boils; in the mid-19th century, this method was used by explorers.[11] Measurement and maps[edit] An important application of the knowledge that atmospheric pressure varies directly with altitude was in determining the height of hills and mountains thanks to the availability of reliable pressure measurement devices. While in 1774 Maskelyne was confirming Newton's theory of gravitation at and on Schiehallion in Scotland (using plumb bob deviation to show the effect of "gravity") and accurately measure elevation, William Roy using barometric pressure was able to confirm his height determinations, the agreement being to within one meter (3.28 feet). This was then a useful tool for survey work and map making and long has continued to be useful. It was part of the "application of science" which gave practical people the insight that applied science could easily and relatively cheaply be "useful".[12] See also[edit] Underwater diving portal Atmosphere (unit) Barometric formula Barotrauma - physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding gas or liquid. Cabin pressurization Effects of high altitude on humans High-pressure area International Standard Atmosphere - a tabulation of typical variation of principal thermodynamic variables of the atmosphere (pressure, density, temperature, etc.) with altitude, at middle latitudes. Low-pressure area NRLMSISE-00 Plenum chamber Pressure Subtropical high belts References[edit] Jump up ^ International Civil Aviation Organization. Manual of the ICAO Standard Atmosphere, Doc 7488-CD, Third Edition, 1993. ISBN 92-9194-004-6. Jump up ^ Sample METAR of CYVR Nav Canada Jump up ^ Montreal Current Weather, CBC Montreal, Canada, retrieved 2014-03-30 Jump up ^ A quick derivation relating altitude to air pressure Archived 2011-09-28 at the Wayback Machine. by Portland State Aerospace Society, 2004, accessed 05032011 ^ Jump up to: a b World: Highest Sea Level Air Pressure Above 750 m, Wmo.asu.edu, 2001-12-19, archived from the original on 2012-10-17, retrieved 2013-04-15 Jump up ^ World: Highest Sea Level Air Pressure Below 750 m, Wmo.asu.edu, 1968-12-31, archived from the original on 2013-05-14, retrieved 2013-04-15 Jump up ^ Kramer, MR; Springer C; Berkman N; Glazer M; Bublil M; Bar-Yishay E; Godfrey S (March 1998). "Rehabilitation of hypoxemic patients with COPD at low altitude at the Dead Sea, the lowest place on earth" (PDF). Chest. 113 (3): 571-575. doi:10.1378/chest.113.3.571. PMID 9515826. Archived from the original (PDF) on 2013-10-29. PMID 9515826 Jump up ^ Chris Landsea (2010-04-21). "Subject: E1), Which is the most intense tropical cyclone on record?". Atlantic Oceanographic and Meteorological Laboratory. Archived from the original on 6 December 2010. Retrieved 2010-11-23. Jump up ^ Vapour Pressure, Hyperphysics.phy-astr.gsu.edu, retrieved 2012-10-17 Jump up ^ High Altitude Cooking, Crisco.com, 2010-09-30, retrieved 2012-10-17 Jump up ^ Berberan-Santos, M. N.; Bodunov, E. N.; Pogliani, L. (1997). "On the barometric formula". American Journal of Physics. 65 (5): 404-412. Bibcode:1997AmJPh..65..404B. doi:10.1119/1.18555. Jump up ^ Hewitt, Rachel, Map of a Nation - a Biography of the Ordnance Survey ISBN 1-84708-098-7 External links[edit] 1976 Standard Atmosphere from NASA Source code and equations for the 1976 Standard Atmosphere A mathematical model of the 1976 U.S. Standard Atmosphere Calculator using multiple units and properties for the 1976 Standard Atmosphere Calculator giving standard air pressure at a specified altitude, or altitude at which a pressure would be standard Real-time map of global mean sea-level pressure Atmospheric calculator and Geometric to Pressure altitude converter Experiments[edit] Movies on atmospheric pressure experiments from Georgia State University's HyperPhysics website - requires QuickTime Test showing a can being crushed after boiling water inside it, then moving it into a tub of ice cold water. [show] v t e Meteorological data and variables [show] v t e Diving medicine, physiology, physics and environment Authority control GND: 4132624-6 NDL: 00565690 Categories: AtmosphereAtmospheric thermodynamicsPressureUnderwater diving physics Navigation menu Not logged inTalkContributionsCreate accountLog inArticleTalkReadEditView historySearch Search Wikipedia Go

Stratosphere

he second major layer of Earth's atmosphere, just above the troposphere,

Atmosphere

the envelope of gases surrounding the earth or another planet.

thermosphere

the region of the atmosphere above the mesosphere