International Standard Atmosphere 696923 225751578 2008-07-15T06:21:20Z Jdlh 4236 /* Description */ Copy-edit the paragraph on geopotential and geometric height, but also tag that it needs a reference to a source for the claim. {{Mergefrom|ICAO Standard Atmosphere|date=June 2007}} {{distinguish|Standard conditions for temperature and pressure}} The '''International Standard Atmosphere''' (ISA) is an [[atmospheric models|atmospheric model]] of how the [[pressure]], [[temperature]], [[density]], and [[viscosity]] of the [[Earth's atmosphere]] change over a wide range of [[altitude]]s. It consists of tables of values at various altitudes, plus some [[formula]]s by which those values were derived. The [[International Organization for Standardization]] (ISO), publishes the ISA as an [[international standard]], ISO 2533:1975.<ref name="ISO 1975"> [[International Organization for Standardization]], ''[http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=7472&ICS1=49&ICS2=20&ICS3= Standard Atmosphere]'', ISO 2533:1975, 1975.</ref> Other [[standards organization]]s, such as the [[International Civil Aviation Organization]] (ICAO) and the [[United States Government]], publish extensions or subsets of the same atmospheric model under their own standards-making authority. ==Description== The ISA model divides the atmosphere into layers with linear temperature distributions.<ref name="Graham Gyatt">Gyatt, Graham ([[2006-01-14]]): [http://www.atmosculator.com/The%20Standard%20Atmosphere.html "The Standard Atmosphere"]. A mathematical model of the 1976 U.S. Standard Atmosphere.</ref> The other values are computed from basic physical constants and relationships. Thus the standard consists of a table of values at various altitudes, plus some [[formula]]s by which those values were derived. For example, at sea level the standard gives a pressure of 1013 [[hPa]] and a temperature of 15 °C, and an initial [[lapse rate]] of −6.5 °C/km. The tabulation continues to 11 km where the pressure has fallen to 22.632 kPa and the temperature to −56.5 °C. Between 11 km and 20 km the temperature remains constant. <ref name="aeromech.usyd.edu.au">{{Citation | last = Auld | first = D.J. | last2 = Srinivas | first2 = K. | title = Properties of the Atmosphere | year = 2008 | url = http://www.aeromech.usyd.edu.au/aero/atmosphere/ | accessdate = 2008-03-13 }}</ref><ref name="Batchelor 1967">Batchelor, G. K., ''An Introduction to Fluid Dynamics'', Cambridge Univ. Press, 1967.</ref> {| class="wikitable" |+ Layers in the ISA |- |+ Standard Atmosphere 1976 ! Layer ! Level<br>Name ! Base<br>Geopotential<br>Height<br> ''h'' (in km) ! Base<br>Geometric<br> Height<br>''z'' (in km) ! <br>Lapse<br>Rate <br> (in °C/km) ! <br>Base<br>Temperature <br> ''T'' (in °C) ! Base<br>Atmospheric<br>Pressure <br>''p'' (in Pa) |- |align=center|0 | align=center|[[Troposphere]] | align=center|0.0 | align=center|0.0 | align=center|−6.5 | align=center|+15.0 | align=center|101,325 |- |align=center|1 | align=center|[[Tropopause]] | align=center|11.000 | align=center|11.019 | align=center|+0.0 | align=center|−56.5 | align=center|22,632 |- |align=center|2 | align=center|[[Stratosphere]] | align=center|20.000 | align=center|20.063 | align=center|+1.0 | align=center|−56.5 | align=center|5,474.9 |- |align=center|3 | align=center|[[Stratosphere]] | align=center|32.000 | align=center|32.162 | align=center|+2.8 | align=center|−44.5 | align=center|868.02 |- |align=center|4 | align=center|[[Stratopause]] | align=center|47.000 | align=center|47.350 | align=center|+0.0 | align=center|−2.5 | align=center|110.91 |- |align=center|5 | align=center|[[Mesosphere]] | align=center|51.000 | align=center|51.413 | align=center|−2.8 | align=center|−2.5 | align=center|66.939 |- |align=center|6 | align=center|[[Mesosphere]] | align=center|71.000 | align=center|71.802 | align=center|−2.0 | align=center|−58.5 | align=center|3.9564 |- |align=center|7 | align=center|[[Mesopause]] | align=center|84.852 | align=center|86.000 | align=center|— | align=center|−86.2 | align=center|0.3734 |} In the above table, geopotential height is calculated from a mathematical model in which the acceleration due to gravity is assumed constant. Geometric height results from the (more accurate) assumption that gravity obeys an inverse square law.{{Fact|date=July 2008}} ==Development of the ISA== The ISA model is based on average conditions at mid latitudes, as determined by ISO's TC 20/SC 6 technical committee. It has been revised from time to time since the middle of the 20th century. ==Other standard atmospheres== The [[International Civil Aviation Organization]] (ICAO) published their "ICAO Standard Atmosphere" as Doc 7488-CD in 1993. It has the same model as the ISA, but extends the altitude coverage to 80 kilometres (262,500 feet).<ref name="ICAO 1993">[[International Civil Aviation Organization]], ''Manual of the ICAO Standard Atmosphere (extended to 80 kilometres (262 500 feet))'', Doc 7488-CD, Third Edition, 1993, ISBN 92-9194-004-6.</ref> The [[U.S. Standard Atmosphere]] is models that define values for atmospheric temperature, density, pressure and other properties over a wide range of altitudes. The first model, based on an existing international standard, was published in 1958 by the U.S. Committee on Extension to the Standard Atmosphere,<ref name="USA 1958">U.S. Extension to the ICAO Standard Atmosphere, U.S. Government Printing Office, Washington, D.C., 1958</ref> and was updated in 1962,<ref name="USA 1962">U.S. Standard Atmosphere, 1962, U.S. Government Printing Office, Washington, D.C., 1962</ref> 1966,<ref name="USA 1966">U.S. Standard Atmosphere Supplements, 1966, U.S. Government Printing Office, Washington, D.C., 1966</ref> and 1976.<ref name="USA 1976">[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770009539_1977009539.pdf U.S. Standard Atmosphere], 1976, U.S. Government Printing Office, Washington, D.C., 1976 (Linked file is 17 MB)</ref> The U.S. Standard Atmosphere, [[ICAO Standard Atmosphere]] and WMO (World Meteorological Organization) standard atmospheres are the same as the ISO International Standard Atmosphere for altitudes up to 32 km.<ref name="NASA GSFC">[[NASA]], [http://modelweb.gsfc.nasa.gov/atmos/us_standard.html "U.S. Standard Atmosphere 1976"]</ref><ref name=Tomasi1998>{{cite journal | author = Tomasi, C. | coauthors = Vitake, V.; De Santis, L.V. | year = 1998 | title = Relative optical mass functions for air, water vapour, ozone and nitrogen dioxide in atmospheric models presenting different latitudinal and seasonal conditions | journal = Meteorology and Atmospheric Physics | volume = 65 | issue = 1 | pages = 11–30 | url = http://www.springerlink.com/index/Q4V134P888772M26.pdf | accessdate = 2007-12-31 | quote = …the ISO (International Organisation for Standardisation) Standard Atmosphere, 1972. This model is identical to the present Standard Atmospheres of ICAO (International Civil Aviation Organization) and WMO (World Meteorological Organization) up to a height of 32 km | doi = 10.1007/BF01030266 }}</ref> [[NRLMSISE-00]] is an [[empirical]], global [[Mathematical model|model]] of the [[Earth's atmosphere]] from ground to space. It models the [[temperature]]s and [[density|densities]] of the atmosphere's components. A primary use of this model is to aid predictions of [[satellite]] orbital decay due to [[atmospheric drag]]. The [[standard conditions for temperature and pressure]] are a model of gas temperature and pressure used in [[chemistry]]. == References == {{refbegin}} * {{cite book | last = Davies | first = Mark | title = The Standard Handbook for Aeronautical and Astronautical Engineers | publisher = McGraw-Hill | location = New York | year = 2003 | isbn = 0071362290 }} <references/> {{refend}} == See also == * [[Density of air]] ==External links== * [http://www.newbyte.co.il/?calculator.php NewByte standard atmosphere calculator and speed converter] [[Category:Atmosphere]] [[Category:atmospheric thermodynamics]] [[Category:aviation terminology]] [[de:Normatmosphäre]] [[es:International Standard Atmosphere]] [[fr:Atmosphère type OACI]] [[nl:Standaardatmosfeer]] [[ja:国際標準大気]] [[pl:Atmosfera wzorcowa]] [[fi:Kansainvälinen standardi-ilmakehä]]