Atmospheric pressure

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Revision as of 21:00, 9 July 2011

(Also called barometric pressure.) The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the “column” of air lying directly above the point in question.

As with any gas, the pressure exerted by the atmosphere is ultimately explainable in terms of bombardment by gas molecules; it is independent of the orientation of the surface on which it acts. Atmospheric pressure is one of the basic meteorological elements.

It is measured by many varieties of barometer and is expressed in several unit systems. The most common unit used is the millibar (1 millibar equals 1000 dynes cm−2). Unique to the science of meteorology is the use of inches (or millimeters) of mercury, that is, the height of a column of mercury that exactly balances the weight of the column of atmosphere the base of which coincides with that of the mercury column. Also employed are units of weight per area and units of force per area.

fraction of 1 atm average altitude
(m) (ft)
1 0 0
1/2 5,486 18,000
1/3 8,376 27,480
1/10 16,132 52,926
1/100 30,901 101,381
1/1000 48,467 159,013
1/10000 69,464 227,899
1/100000 86,282 283,076

Also See

Reference

• Wikipedia see Atmospheric pressure [1]