# standard atmosphere

standard atmosphere
1. an arbitrarily determined vertical distribution of atmospheric pressure, temperature, and density, assumed to have physical constants and conforming to parametric equations, used for calculations in ballistics, the design of pressure altimeters, etc.
2. a standard unit of atmospheric pressure, having a value of 1013.2 millibars or 29.9213 in. (760 mm) of mercury.

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▪ atmospheric model
atmospheric model with a given vertical distribution of temperature, pressure, and humidity, which by international agreement is taken as a worldwide average of these parameters.

In such a model, the atmosphere is assumed to obey the perfect gas law and to be in hydrostatic equilibrium (i.e., without accelerations of the air in the vertical direction). Further assumptions are that the air is dry and that the acceleration of gravity does not change with height.

Under the above conditions, the vertical variations of pressure and density may be determined for a given set of values at sea level and for any vertical distribution of temperature. Even though the real atmosphere may vary considerably from the assumed standard atmosphere, the latter is useful for such purposes as pressure altimeter calibrations, aircraft and missile designs, ballistic trajectories, and other problems. For many of these purposes, deviations of the real atmosphere from the standard do not cause serious errors in the calculations.

▪ unit of measurement
unit of pressure, equal to the mean atmospheric pressure at sea level. It corresponds to the pressure exerted by a vertical column of mercury (as in a barometer) 760 mm (29.9213 inches) high. One standard atmosphere, which is also referred to as one atmosphere, is equivalent to 101,325 pascals, or newtons of force per square metre (approximately 14.7 pounds per square inch). See also millibar.

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Universalium. 2010.

### Look at other dictionaries:

• Standard atmosphere — can refer to:* A standard reference value for air pressure: ** Atmosphere (unit), an approximation of the value at sea level ** Atmospheric pressure, other reference values * A model of how atmospheric pressure varies with altitude: ** The U.S.… …   Wikipedia

• standard atmosphere — noun a unit of pressure: the pressure that will support a column of mercury 760 mm high at sea level and 0 degrees centigrade • Syn: ↑atmosphere, ↑atm, ↑standard pressure • Hypernyms: ↑pressure unit • Hyponyms: ↑STP, ↑ …   Useful english dictionary

• standard atmosphere — fizikinė atmosfera statusas T sritis automatika atitikmenys: angl. standard atmosphere vok. physikalische Atmosphäre, f rus. атмосфера физическая, f pranc. atmosphère normale, f …   Automatikos terminų žodynas

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• standard atmosphere — /stændəd ˈætməsfɪə/ (say standuhd atmuhsfear) noun 1. Physics any hypothetical atmosphere the physical properties of which are given arbitrary values approximating to mean conditions, for such purposes as comparing the performance of aircraft,… …

• standard atmosphere —    see atmosphere …   Dictionary of units of measurement

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• standard atmosphere — Condition when air is at 14.7 psia pressure. at 68 0F (20 0C) temperature and a relative humidity of 36 percent …   Dictionary of automotive terms

• International Standard Atmosphere — 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,… …   Wikipedia

• U.S. Standard Atmosphere — The U.S. Standard Atmosphere is a series of 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… …   Wikipedia

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