Static pressure exerted by the weight of the atmosphere
"Air pressure" redirects here. For the pressure of air in other systems, see 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] 760mm Hg, 29.9212inchesHg, or 14.696psi.[2] The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth; that is, the Earth's atmospheric pressure at sea level is approximately 1 atm.
In most circumstances, atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. As elevation increases, there is less overlying atmospheric mass, so atmospheric pressure decreases with increasing elevation. Because the atmosphere is thin relative to the Earth's radius—especially the dense atmospheric layer at low altitudes—the Earth's gravitational acceleration as a function of altitude can be approximated as constant and contributes little to this fall-off. Pressure measures force per unit area, with SI units of pascals (1 pascal = 1 newton per square metre, 1N/m2). On average, a column of air with a cross-sectional area of 1 square centimetre (cm2), measured from the mean (average) sea level to the top of Earth's atmosphere, has a mass of about 1.03 kilogram and exerts a force or "weight" of about 10.1 newtons, resulting in a pressure of 10.1 N/cm2 or 101kN/m2 (101 kilopascals, kPa). A column of air with a cross-sectional area of 1in2 would have a weight of about 14.7lbf, resulting in a pressure of 14.7lbf/in2.
^"Statement (2001)". BIPM. Retrieved 2022-03-19.
^International Civil Aviation Organization. Manual of the ICAO Standard Atmosphere, Doc 7488-CD, Third Edition, 1993. ISBN 92-9194-004-6.
and 23 Related for: Atmospheric pressure information
Atmosphericpressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard...
environmental pressure. A liquid in a partial vacuum, i.e., under a lower pressure, has a lower boiling point than when that liquid is at atmosphericpressure. Because...
An atmospheric diving suit (ADS) is a small one-person articulated submersible which resembles a suit of armour, with elaborate pressure joints to allow...
traditional unit of pressure in the imperial and US customary systems. Pressure may also be expressed in terms of standard atmosphericpressure; the unit atmosphere...
which the vapor pressure equals the ambient atmosphericpressure. With any incremental increase in that temperature, the vapor pressure becomes sufficient...
weather. The average atmosphericpressure on the Earth's surface varies between 940 and 1040 hPa (mbar). The average atmosphericpressure at sea level is 1013...
gauges measure pressure relative to atmosphericpressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything...
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmosphericpressure, caused by a sound wave...
Given an atmosphericpressure measurement, the pressure altitude is the imputed altitude that the International Standard Atmosphere (ISA) model predicts...
reduced pressure at the top of the siphon. Then atmosphericpressure was able to push the liquid from the upper reservoir, up into the reduced pressure at...
intrapleural pressure refers to the pressure within the pleural cavity. Normally, the pressure within the pleural cavity is slightly less than the atmospheric pressure...
4% over the entire atmosphere. Air composition, temperature, and atmosphericpressure vary with altitude. Within the atmosphere, air suitable for use in...
Within the atmosphere, the ambient pressure decreases as elevation increases. By measuring ambient atmosphericpressure, a pilot may determine altitude (see...
by the weight of the vertical column of atmospheric gases. In said atmospheric model, the atmosphericpressure, the weight of the mass of the gas, decreases...
the ion source. Atmospheric-pressure chemical ionization is a form of chemical ionization using a solvent spray at atmosphericpressure. A spray of solvent...
airway pressure (CPAP) is a form of positive airway pressure (PAP) ventilation in which a constant level of pressure greater than atmosphericpressure is...
context (e.g., aviation, geometry, geographical survey, sport, or atmosphericpressure). Although the term altitude is commonly used to mean the height...
temperature and pressure has very little meaning and can cause confusion. The molar volume of gases around STP and at atmosphericpressure can be calculated...
combined pressure is known as absolute pressure, and the relationship is: Absolute pressure (bar abs) = gauge pressure(bar) + atmosphericpressure (about...
for the expression freestream static pressure. Gracey has written "The static pressure is the atmosphericpressure at the flight level of the aircraft"...
Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation...
liquid's atmosphericpressure boiling point corresponds to the temperature at which its vapor pressure is equal to the surrounding atmosphericpressure and...
In hydrodynamics and hydrostatics, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which...
Global Information