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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]
It is defined as the pressure exerted by a column of water of 1 inch in height at defined conditions. At a temperature of 4 °C (39.2 °F) pure water has its highest density (1000 kg/m 3). At that temperature and assuming the standard acceleration of gravity, 1 inAq is approximately 249.082 pascals (0.0361263 psi). [2]
According to the American National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480 × 10 18 kg with an annual range due to water vapor of 1.2 or 1.5 × 10 15 kg, depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate.
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.
Air pressure in an automobile tire relative to atmosphere (gauge pressure) [citation needed] +210 to +900 kPa +30 to +130 psi Air pressure in a bicycle tire relative to atmosphere (gauge pressure) [57] 300 kPa 50 psi Water pressure of a garden hose [58] 300 to 700 kPa 50–100 psi Typical water pressure of a municipal water supply in the US [59]
But there’s also a worst-case scenario, where downtown L.A., Long Beach and Redondo Beach could get more than 1.6 inches of rain, and Santa Clarita more than 1.8 inches, Santa Barbara more than ...
Ambient pressure may in other circumstances be measured in pounds per square inch (psi) or in standard atmospheres (atm). The ambient pressure at sea level is approximately one atmosphere, which is equal to 1.01325 bars (14.6959 psi), which is close enough for bar and atm to be used interchangeably in many applications.
A second person has died in a swollen Oregon waterway after atmospheric rivers have pummeled the Pacific Northwest with two bouts of more than 9 inches of rain.