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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 ]
Mars has a very thin atmosphere – the pressure is only 1 ⁄ 160 of earth atmospheric pressure – so a huge balloon would be needed even for a tiny lifting effect. Overcoming the weight of such a balloon would be difficult, but several proposals to explore Mars with balloons have been made. [15] Venus has a CO 2 atmosphere.
Pressure as a function of the height above the sea level. There are two equations for computing pressure as a function of height. The first equation is applicable to the atmospheric layers in which the temperature is assumed to vary with altitude at a non null lapse rate of : = [,, ()] ′, The second equation is applicable to the atmospheric layers in which the temperature is assumed not to ...
Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather . If the entire mass of the atmosphere had a uniform density equal to sea-level density (about 1.2 kg/m 3 ) from sea level upwards, it would terminate abruptly at an altitude of 8.50 ...
In aviation, pressure altitude is the height above a standard datum plane (SDP), which is a theoretical level where the weight of the atmosphere is 29.921 inches of mercury (1,013.2 mbar; 14.696 psi) as measured by a barometer. [2]
The International Standard Atmosphere (ISA) is a static atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations. It has been established to provide a common reference for temperature and pressure and consists of tables of values at various altitudes ...
When these fluctuations were explained as a manifestation of changes in atmospheric pressure, the science of meteorology was born. Over time, 760 millimeters of mercury at 0 °C came to be regarded as the standard atmospheric pressure. In honour of Torricelli, the torr was defined as a unit of pressure equal to one millimeter of mercury at 0 °C.
According to the International Standard Atmosphere, at a pressure of 1 atm and a temperature of 15° C, air has a density of approximately 1.225 kilograms per cubic metre (kg/m 3), about 1 ⁄ 1000 the density of liquid water. atmospheric lake A long-lived pool of water vapor. atmospheric model atmospheric pressure (p) Also barometric pressure.