Marine Glossary

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atmospheric pressure

The pressure exerted by the weight of the earth's atmosphere, which is about 14.7 pounds per square inch. The conventional pressure units used in marine weather is the millibar which is the same as a hectopascal.

The approximate average pressure worldwide throughout the year is about 1013 mb. Typical extreme values are 950 mb and 1050 mb. All-time world record high pressure is 1083.8 mb at Agata, Siberia, on December 31, 1968, although most other world records by country are closer to 1060 to 1070 mb, and these are also mostly over land. Record low records are all in the eyes of hurricanes, and include the record Typhoon Tip in the Pacific Ocean at 870 mb on October 12, 1979.

Average pressures for Jan and July worldwide are in the WXT World Atlas and in Chapter 10 of The Barometer Handbook.

See standard atmosphere and related discussion in WXT ART-5 on barometers and WXT ART-2 on wind as well as in online course questions on these topics.

WXT G120 compares barometric pressure measured in different units. WXT G138 shows the typical diurnal variation of atmospheric pressure in the tropics.