>From the World Meteorological Organization: 3.1.2 Units and scales The basic unit for atmospheric pressure measurements is the pascal (Pa) (or newton per square metre). It is accepted practice to add the prefix "hecto" to this unit when reporting pressure for meteorological purposes, making the hectopascal (hPa), equal to 100 Pa, the preferred terminology. This is largely because one hectopascal equals one millibar (mbar), the formerly used unit.
The scales of all barometers used for meteorological purposes should be graduated in hPa. Some barometers are graduated in "millimetres or inches of mercury under standard conditions", (mm Hg)n and (in Hg)n, respectively. When it is clear from the context that standard conditions are implied, the briefer terms "millimetre of mercury" or "inch of mercury" may be used. Under these standard conditions, a column of mercury having a true scale height of 760 (mm Hg)n exerts a pressure of 1 013.250 hPa. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Michael Payne Sent: Wednesday, 07 March 2012 12:36 To: U.S. Metric Association Subject: [USMA:51491] millibar depreciated I'm trying to get my company to replace millibar with hectopascal in company manuals and was looking for an authoritative source that states this. Anyone have an idea? I was under the impression that millibar was depreciated. In my travels as a pilot worldwide it seems the pressure stated most outside north America is hectopascals for atmospheric pressure, mainly because it's the same as a millibar. I do have http://www.unitconversion.org/pressure/bar-conversion.html, but would prefer a website with more authority, a government or educational website would be best.. Wikipedia does not seem to have this included, with good sources I'd include it. Regards, Michael Payne
