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Meteorological instruments -- Measurement of Atmospheric Pressure

Mercury Barometer

Mercury barometer is a standard type of barometer used at manned and climatological weather stations throughout the world.   This mercury-in-glass barometer is assigned to be the station barometer for the Hong Kong Observatory to measure atmospheric pressure every hour.  Correction for index error, adjustment of the readings to the standard temperature of zero degree Celsius and the standard gravity of 9.80665 metres per square second  and reduction to mean sea-level are made using the methods described in 'World Meteorological Organization (WMO) publication No.8, Guide to Meteorological Instruments and Methods of Observation'.