A Brief Note on Standard/Reference Atmospheres
MJ Mahoney
Created: Oct 17, 2005
Last Revision: Oct 18, 2005
A standard atmosphere
describes the vertical profile of pressure, temperature, and density
through the Earth's atmosphere, and these are normally arrived at by
international agreement. Reference atmospheres on the other hand tend
to be created for specific geographical locations, although they can be
gobal as well. Both standard and reference atmospheres are also used to
describe atmospheric composition.
Standard atmopheres first appeared after World War I with the growth of
international air transport, which required international standards.
The first US Standard
Atmosphere was publishcd by the US National Committee for Aeronautics
(NACA) in 1925. Later, in 1952, NACA adopted the International Civil
Aviation Organization's (ICAO) Standard Atmosphere. The ICAO, which is headquartered in
Montreal, Canada,
was established by the United Nations in 1947. It has 187 member
nations with the goal of establishing international civil aviation
standards. The ICAO standard
atmosphere, also known as the International Standard Atmosphere (ISA),
was extended from 20 km to 32 km in 1964, and to 80 km in 1993 (Reference).
In 1975 the
International Strandards Organization (ISO) published a standard
atmosphere to 50 km, and later to 80 km. The US Committee on Extension
to the Standard Atmosphere (COESA) published a revised US Standard
Atmosphere in 1976 which extends to 100km. The US Standard Atmosphere
(1976) is identical to the ICAO Standard Atmosphere to 32 km, and to
the ISO Standard Atmosphere to 50 km. Above about 100 km, the solar
cycle and geomagnetic activity introduce substantial variations in the
temperature and density of the atmosphere.
Manual
of the ICAO Standard Atmosphere (extended to 80 kilometres (262 500
feet)), Doc 7488 / Third Edition, 1993.