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The standard atmosphere was originally defined as the pressure exerted by a 760 mm column of mercury at 0 °C (32 °F) and standard gravity (g n = 9.806 65 m/s 2). [2] It was used as a reference condition for physical and chemical properties, and the definition of the centigrade temperature scale set 100 °C as the boiling point of water at this pressure.
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth.The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa), which is equivalent to 1,013.25 millibars, [1] 760 mm Hg, 29.9212 inches Hg, or 14.696 psi. [2]
The depth of the planetary boundary layer ranges from as little as about 100 metres (330 ft) on clear, calm nights to 3,000 m (9,800 ft) or more during the afternoon in dry regions. The average temperature of the atmosphere at Earth's surface is 14 °C (57 °F; 287 K) [30] or 15 °C (59 °F; 288 K), [31] depending on the reference. [32] [33] [34]
0.333 atm [3] Pressurized passenger aircraft cabin altitude 8,000 ft (2,400 m) 0.76 atm [4] Sea level atmospheric pressure: 1 atm Surface of Titan: 1.45 atm 10 m depth in seawater: 2 atm 20 m depth in seawater 3 atm Recreational diving depth limit (40 m) [5] 5 atm Common technical diving depth limit (100 m) [6] [7] 11 atm
The pressure of seawater at a depth of 33 feet equals one atmosphere. The absolute pressure at 33 feet depth in sea water is the sum of atmospheric and hydrostatic pressure for that depth, and is 66 fsw, or two atmospheres absolute. For every additional 33 feet of depth, another atmosphere of pressure accumulates. [6]
In 1979, oceanographer Sylvia Earle set a human depth record of 1,250 feet (381 m) using a JIM suit. [ 2 ] The Arctic dives of 1976 proved that the JIM was capable of performing oilfield operations in very cold and very deep water; the average water temperature at the wellhead was measured at −1.6 °C (29.1 °F), while the average internal ...
A standard atmosphere is defined by the World Meteorological Organization as "a hypothetical vertical distribution of atmospheric temperature, pressure and density which, by international agreement, is roughly representative of year-round, midlatitude conditions."
Because pressure in the ocean increases by about 1 atmosphere for every 10 meters of depth, the amount of pressure experienced by many marine organisms is extreme. Until recent years, the scientific community lacked detailed information about the effects of pressure on most deep sea organisms because the specimens encountered arrived at the ...