millibar

A unit of pressure equal to 1000 baryes. The barye (bar) is the unit of pressure in the CGS (centimeter-gram-second) system. By definition, a barye is equal to the pressure exerted by a force of one dyne (1 dyn) over a surface of one square centimeter (1 barye = 1 dyn/cm²). A barye is one millionth of a bar, in turn equivalent to one tenth of a pascal (Pa), which is the unit of pressure in the International System (SI). From the above it follows that one millibar (1 mb) equals one hectopascal (1 hPa) [one hundred pascals]. This equivalence (1 mb = 1 hPa) means that isobar values on a surface map can be expressed indistinctly in millibars or hectopascals. The progressive adoption of the SI over the CGS means the hectopascal is increasingly used over the millibar, with the latter falling into progressive disuse.