ESS124
Prof. Jin-Yi Yu
Units of Atmospheric Pressure
• Pascal (Pa): a SI (Systeme Internationale) unit for air pressure.
•     1 Pa = a force of 1 newton acting on a surface of one square  
•                 meter
•      1 hectopascal (hPa) = 1 millibar (mb)  [hecto = one hundred =100]
•Bar: a more popular unit for air pressure.
•     1 bar = a force of 100,000 newtons acting on a surface of one
•                  square meter
•              = 100,000 Pa
•              = 1000 hPa
•              = 1000 mb
•One atmospheric pressure = standard value of atmospheric pressure at lea level = 1013.25 mb = 1013.25 hPa.