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International Standard Atmosphere



 It has been suggested that ICAO Standard Atmosphere be merged into this article or section. (Discuss)


The International Standard Atmosphere (ISA) is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes. It consists of tables of values at various altitudes, plus some formulas by which those values were derived. The International Organization for Standardization (ISO), publishes the ISA as an international standard, ISO 2533:1975.[1] Other standards organizations, 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.

Contents

Description

The ISA model divides the atmosphere into layers with linear temperature distributions.[2] 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 formulas by which those values were derived. For example, at sea level the standard gives a pressure of 101.3 kPa and a temperature of 15 °C, and an initial lapse rate of −6.5 °C/km. Above 12 km the tabulated temperature is essentially constant. The tabulation continues to 18 km where the pressure has fallen to 7.5 kPa and the temperature to −56.5 °C.[3][4]

Layers in the ISA Standard Atmosphere 1976
Layer Level
Name 		Base
Geopotential
Height
h (in km) 		Base
Geometric
Height
z (in km)
Lapse
Rate
(in °C/km)
Base
Temperature
T (in °C) 		Base
Atmospheric
Pressure
p (in Pa)
0 Troposphere 0.0 0.0 −6.5 +15.0 101,325
1 Tropopause 11.000 11.019 +0.0 −56.5 22,632
2 Stratosphere 20.000 20.063 +1.0 −56.5 5,474.9
3 Stratosphere 32.000 32.162 +2.8 −44.5 868.02
4 Stratopause 47.000 47.350 +0.0 −2.5 110.91
5 Mesosphere 51.000 51.413 −2.8 −2.5 66.939
6 Mesosphere 71.000 71.802 −2.0 −58.5 3.9564
7 Mesopause 84.852 86.000 — −86.2 0.3734

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).[5]

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,[6] and was updated in 1962,[7] 1966,[8] and 1976.[9] The U.S. Standard Atmosphere, ICAO Standard Atmosphere and WMO standard atmospheres are the same as the ISO International Standard Atmosphere for altitudes up to 32 km.[10][11]

NRLMSISE-00 is an empirical, global model of the Earth's atmosphere from ground to space. It models the temperatures and 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

  • Davies, Mark (2003). The Standard Handbook for Aeronautical and Astronautical Engineers. New York: McGraw-Hill. ISBN 0071362290. 
  1. ^ International Organization for Standardization, Standard Atmosphere, ISO 2533:1975, 1975.
  2. ^ Gyatt, Graham (2006-01-14): "The Standard Atmosphere". A mathematical model of the 1976 U.S. Standard Atmosphere.
  3. ^ http://www.aeromech.usyd.edu.au/aero/atmos/atmtab.html, Tabulation of 1976 standard at University of Sydney aeronautical mechanics site
  4. ^ Batchelor, G. K., An Introduction to Fluid Dynamics, Cambridge Univ. Press, 1967.
  5. ^ 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.
  6. ^ U.S. Extension to the ICAO Standard Atmosphere, U.S. Government Printing Office, Washington, D.C., 1958
  7. ^ U.S. Standard Atmosphere, 1962, U.S. Government Printing Office, Washington, D.C., 1962
  8. ^ U.S. Standard Atmosphere Supplements, 1966, U.S. Government Printing Office, Washington, D.C., 1966
  9. ^ U.S. Standard Atmosphere, 1976, U.S. Government Printing Office, Washington, D.C., 1976 (Linked file is 17 MB)
  10. ^ NASA, "U.S. Standard Atmosphere 1976"
  11. ^ Tomasi, C.; Vitake, V.; De Santis, L.V. (1998). "Relative optical mass functions for air, water vapour, ozone and nitrogen dioxide in atmospheric models presenting different latitudinal and seasonal conditions". Meteorology and Atmospheric Physics 65 (1): 11-30. Retrieved on 2007-12-31. “…the ISO (International Standards Organization) 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”

See also

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "International_Standard_Atmosphere". A list of authors is available in Wikipedia.
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