The international unit of meteorological air pressure is hectopascals (hP), which is equivalent to millibars (mb).
Standard air pressure at sea level is 1013.25 mb. The highest air pressure recorded was 1084 mb in Siberia. The lowest air pressure, 870 mb, was recorded in a typhoon in the Pacific Ocean
Air pressure rises and falls about 3 mb in daily cycles, regardless of weather
. Meteorologists take these fluctuations into account when they analyze changes in air pressure to interpret if the changes are due to weather
systems. A large drop of 7 mb or more, in 24 hours, may indicate a high-pressure system is moving out and/or a low-pressure system is moving in.
ASOS Pressure Algorithm ~ National Weather Service Training Center
Once every ten seconds the two digital barometers (Class I system) or three digital barometers (Class II system) provide pressure readings for the observing site.
If you have a Class I system with two barometers, the six readings taken every minute are sent to algorithms for processing and comparison. If you have a Class III system with three barometers, the same process occurs but here you have three readings to compare.
If one or more of the 6 pressure values obtained during a one-minute period are missing, the sensor is automatically logged as "inoperative". It can only be returned to "operational status" by a maintenance
Once the sensor data has been determined, the further processing by the pressure algorithms takes place so as to provide additional pressure parameter information