Millibar

The millibar (abbreviated "mb" or "mbar") is a unit of pressure commonly used in meteorology.

Conversion factors from mb to other common units are:

1 mb =

    = 100 Pascals (100 Pa)
    = 1000 Dynes per square centimeter (1000 Dyne/cm^2)
    = 760/1013.25 Torr (0.750062 torr)
    = 29.92126/1013.25 Inches of mercury (0.029530 in.Hg)
    = 1/1013.25 Standard Terrestrial Atmospheres 
      (0.000986923 Std.Atm.)

Historically, the millibar was introduced by meteorologist Sir Napier Shaw in 1909 as a replacement for manometric measures of pressure (such as torr, inches of mercury, and standard atmospheres), which are defined according to standard conditions. The millibar is a force-based measure of pressure, making it suitable for direct measurement of pressure under non-standard conditions.

This makes the millibar an accurate measure of pressure for high altitude and space travel applications.

The millibar was adopted by the World Meteorological Association in 1914, but as of 1971 is no longer endorsed as a SI (metric system) unit. The Pascal has since become the preferred SI unit of pressure. However, the original definition of the millibar was chosen for ready conversion to Pascals, and this has allowed meteorological literature to continue widespread use of the millibar alongside SI units without confusion.