Sea-level pressure

Sea-level pressure or mean sea-level pressure (MSL or MSLP) is the standard that different weather stations employ to compare barometric pressure readings, which are made in inches of mercury. After the barometric pressure at a location is read, it is corrected to indicate the sea-level pressure. The correction is based on the height of the mercurial barometer above mean sea level. A correction exists for every mercurial barometer. Ships at sea and low-lying weather stations must add a small correction such as +0.03 to their barometric pressure readings (called "station pressure") to obtain the sea-level pressure.

Sea-level pressure values are used to draw weather maps called "surface charts," which are the commonplace weather maps that may be seen on the Internet and on television stations.

Average sea-level pressure is 29.923 inches of mercury (Hg) or 1013.2 millibars (1013.2 hectopascals) (hPa) (SI). Sea-level pressure is transmitted around the world in millibars (hectopascals). In the weather code, three digits are all that is needed. 1013.2 millibars is transmitted as 132; 1000.0 millibars is transmitted as 000; 998.7 millibars is transmitted as 987; etc. The highest sea-level pressure on earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1032.0 millibars. The lowest measurable sea-level pressure is found at the centers of hurricanes (typhoons, baguios).

See also

Atmospheric pressure

External links

http://www.weather.com