  atmospheric pressure is the force per unit area exerted on a surface by the weight of air above that surface in the atmosphere of earth (or that of another planet). in most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. on a given plane, low-pressure areas have less atmospheric mass above their location, whereas high-pressure areas have more atmospheric mass above their location. likewise, as elevation increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation. on average, a column of air one square centimeter in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03&nbsp;kg and weight of about 10.1&nbsp;n (2.28&nbsp;lbf) (a column one square inch in cross-section would have a weight of about 14.7&nbsp;lbs, or about 65.4&nbsp;n). == standard atmosphere == the standard atmosphere (symbol: atm) is a unit of pressure equal to 101325 painternational civil aviation organization, manual of the icao standard atmosphere, doc 7488-cd, third edition, 1993, isbn 92-9194-004-6. or 1013.25 hectopascals or millibars. equivalent to 760 mmhg (torr), 29.92 inhg, 14.696 psi. (the pascal is a newton per square meter or in terms of si base units, kilogram per meter per second-squared.) == mean sea level pressure ==   the mean sea level pressure (mslp) is the atmospheric pressure at sea level or (when measured at a given elevation on land) the station pressure adjusted to sea level assuming that the temperature falls at a lapse rate of 6.5 k per km in the fictive layer of air between the station and sea level. this is the atmospheric pressure normally given in weather reports on radio, television, and newspapers or on the internet. when barometers in the home are set to match the local weather reports, they measure pressure adjusted to sea level, not the actual local atmospheric pressure. the adjustment to sea level means that the normal range of fluctuations in atmospheric pressure is the same for everyone. the pressures that are considered high pressure or low pressure do no
Atmosphere Atmospheric_thermodynamics Pressure Underwater_diving_physics