The bar (symbol bar), decibar (symbol dbar) and the millibar (symbol mbar, also mb) are units of pressure. They are not SI units, but they are accepted (although discouraged) for use with the SI. The bar is still widely used in descriptions of pressure because it is about the same as atmospheric pressure. The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin in Canberra, Australia. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... Look up si, Si, SI in Wiktionary, the free dictionary. ...

Definition

The bar, decibar and millibar are defined as:

• 1 bar = 100,000 pascals (Pa) = 1,000,000 dynes per square centimeter (baryes)
• 1 dbar = 0.1 bar = 10,000 Pa = 100,000 dyn/cm²
• 1 mbar = 0.001 bar = 100 Pa = 1,000 dyn/cm²

(A pascal is one newton per square meter.) In physics, the dyne is a unit of force specified in the centimetre-gram-second (cgs) system of units, symbol dyn. One dyne is equal to exactly 10-5 newtons. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ... The barye (symbol: Ba) is the centimetre-gram-second (CGS) unit of pressure. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... The newton (symbol: N) is the SI unit of force. ...

Origin

The word bar has its origin in the Greek word βάρος (baros), meaning weight. Its official symbol is "bar"; the earlier "b" is now deprecated, but still often seen especially as "mb" rather than the proper "mbar" for millibars. A spring scale measures the weight of an object In the physical sciences, weight is a measurement of the gravitational force acting on an object. ...

The bar and millibar were introduced by Sir Napier Shaw in 1909 and internationally adopted in 1929. Sir Napier Shaw (March 4, 1854 - March 23, 1945), British meteorologist. ...

Discussion

Atmospheric air pressure is often given in millibars where "standard" sea level pressure is defined as 1013.25 mbar (hPa), equal to 1.01325 bar. Despite millibars not being an SI unit, they are still used locally in meteorology to describe atmospheric pressure. The SI unit is the pascal (Pa), with 1 mbar = 100 Pa = 1 hPa = 0.1 kPa. Meteorologists worldwide have long measured air pressure in millibars. After the introduction of SI units, many preferred to preserve the customary pressure figures. Therefore, some continue to use millibars under their own name, while others use hectopascals (which are equivalent to millibars) so they could stick to the same numeric scale. Similar pressures are given in kilopascals in practically all other fields, where the hecto prefix is hardly ever used. In particular, Canadian weather reports use kilopascals (which could also be called centibars). Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... Look up si, Si, SI in Wiktionary, the free dictionary. ... The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ...

Americans are familiar with the millibar in US reports of hurricanes and other cyclonic storms, where lower central pressure generally means higher winds and a stronger storm. This article is about weather phenomena. ...

In everyday use, pressure is often measured with reference to atmospheric pressure. This is gauge pressure and denoted by barg, often written with no spaces, spoken "bar gauge", and sometimes using symbols such as 'bar(g)'. For example, if someone says that their car tires are pressurised to 2.3 bar they actually mean bar gauge: the pressure in the tire is really 3.3 bar, but only 2.3 bar above atmospheric, which is the scale a tire gauge would read. When absolute pressure is desired, it is sometimes denoted 'bara' or 'bar(a)' for "bar absolute". The alteration of units of measure for this purpose is now deprecated, with qualification of the physical property being preferred, e.g., "The gauge pressure is 2.3 bar; the absolute pressure is 3.3 bar".

In water, a measurement in decibars is approximately equal to the depth in meters; 1 decibar occurs at a depth of 1.019716 m.

Unicode has a character for "mb": (㏔), but exists only for compatibility with legacy Asian encodings; it should not be used in new texts. Unicode is an industry standard designed to allow text and symbols from all of the writing systems of the world to be consistently represented and manipulated by computers. ...

Example reading: 1 Pa = 1 N/m²  = 10⁻⁵ bar  = 10.197×10⁻⁶ at  = 9.8692×10⁻⁶ atm ....etc.
Note: mmHg is an abbreviation for millimetres of mercury. The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Youngs modulus and tensile strength). ... A technical atmosphere (symbol: at) is a non-SI unit of pressure equal to 1 kilogram-force per square centimeter, i. ... Standard atmosphere (symbol: atm) is a unit of pressure. ... For the standard botanical author abbreviation Torr. ... A pressure gauge reading in PSI (red scale) and kPa (black scale) The pound-force per square inch (symbol: lbf/in²) is a non-SI unit of pressure based on avoirdupois units. ... The newton (symbol: N) is the SI unit of force. ... In physics, the dyne is a unit of force specified in the centimetre-gram-second (cgs) system of units, symbol dyn. One dyne is equal to exactly 10-5 newtons. ... The deprecated unit kilogram-force (kgf) or kilopond (kp) is the force exerted by one kilogram of mass in standard Earth gravity (defined as exactly 9. ... Standard atmosphere (symbol: atm) is a unit of pressure. ... For the standard botanical author abbreviation Torr. ... The pound-force is a non-SI unit of force or weight (properly abbreviated lbf or lbf). The pound-force is equal to a mass of one pound multiplied by the standard acceleration due to gravity on Earth (which is defined as exactly 9. ...

External links

• Official SI website: Table 8. Non-SI units accepted for use with the SI
• Conversion factors from bar to various pressure units

See also

• Conversion of units