Bar (unit) (symbol: cbar), and millibar (symbol: mbar or mb). The notation bar(g), though deprecated by various bodies, represents gauge pressure, i.e., pressure in bars above ambient or atmospheric pressure. The bar is defined using the SI derived unit, pascal: ≡ 100,000 Pa ≡ 100,000 N/m. Thus, is equal to: and 1 bar is approximately equal to: Notes: The word "bar" has its origin in the Greek word (), meaning weight. The unit's official symbol is bar; the earlier symbol b is now deprecated and conflicts with the use of b denoting the unit barn, but it is still encountered, especially as
Dobson unit when plugged into the real gas law, the number density of air is found by using pressure, temperature and the real gas constant. formula_3 The number density (molecules/volume) of air at standard temperature and pressure (T = 273K and P = 101325 Pa) is, by using this equation: formula_4 With some unit conversions of Joules to Pascals, the equation for molecules/volume is formula_5 A Dobson Unit is the total amount of a trace gas per unit area. In atmospheric sciences, this is referred to as a column density. How, though, do we go from units of molecules per cubic meter,