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.
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 1.013 bar and a temperature of 15°C, and an initial
lapse rate of -6.5 °C/km. Above 12km the tabulated temperature is essentially constant. The tabulation continues to 18km where the pressure has fallen to 0.075 bar 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 is the same as the ICAO Standard Atmosphere for altitudes up to 32km.
[10]
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
★
The Standard Handbook for Aeronautical and Astronautical Engineers, , Mark, Davies, McGraw-Hill, 2003,
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"
See also
★
Density of air
External links
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