Barometric pressure
From KayakWiki
What is the barometric pressure?
When barometric pressures are reported, the actual air pressure at a location is adjusted by a standard formula to reflect what the equivalent pressure would be at sea level. Using sea level as a common reference allows one to compare pressure at different locations meaningfully. This can be done since there is a well-defined relationship between pressure and altitude. This in turn allows one to use a barometer to determine altitude.
This means that if you use a small barometer such as in a watch or weather meter, the barometric pressure you observe will not match the weather report from a weather bureau.
Barometric pressure is the pressure at sea level in the atmosphere. The instrument used to measure atmospheric pressure is a barometer.
Barometric pressures are quoted in units of pressure - force per unit area. These are pounds per square inch (psi), kiloPascals (kPa) or millibars (mb). However, since some barometers use a column of mercury to measure pressure, barometric pressure is also specified as the height of the column in inches of mercury (in Hg) or millimeters of mercury (mmHg).
Standard atmospheric pressure is
- 1013 mb
- 101.3 kPa
- 29.92 inHg
- 760 mmHg
- 760 Torr
- 14.7 psi
As a rule, if pressure is rising quickly, fair weather is coming in. If the barometric pressure is falling, foul weather is coming. However, pressure alone is not the best indicator of coming weather and it is good to learn to watch for other signs, such as cloud formations to determine what is likely to happen in the near future.
Small electronic barometers are now available. They are included in some multi-function watches and in weather meters.
