Usage
Atmospheric air pressure is often given in millibars where standard sea level pressure is defined as 1000 mbar, 100 (kPa), or 1 bar. This should be distinguished from the now deprecated unit of pressure, known as the "atmosphere" (atm), which is equal to 1.01325 bar. Despite millibars not being an SI unit, meteorologists and weather reporters worldwide have long measured air pressure in millibars as the values are convenient. After the advent of SI units, some meteorologists began using hectopascals (symbol hPa) which are numerically equivalent to millibars. For example, the weather office of Environment Canada uses kilopascals and hectopascals on their weather maps. In contrast, Americans are familiar with the use of the millibar in US reports of hurricanes and other cyclonic storms.
In water, there is an approximate numerical equivalence between the change in pressure in decibars and the change in depth from the sea surface in metres. Specifically, an increase of 1 decibar occurs for every 1.019716 metre increase in depth close to the surface. As a result, decibars are commonly used in oceanography.
Many engineers worldwide use the bar as a unit of pressure because, in much of their work, using pascals would involve using very large numbers.
In the automotive field, turbocharger boost is often described in bars in the metric part of the world (i.e., outside the US).
Unicode has a character for "mb": ㏔, U+33D4, but it exists only for compatibility with legacy Asian encodings. There is also a character "bar": ㍴, U+3374.
The kilobar is commonly used in geological systems, particularly in experimental petrology.
Read more about this topic: Bar (unit)
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