Atmospheric pressure, sometimes also called
barometric pressure, is the pressure exerted by the weight of air 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 kg and weight of about 10.1 N (2.28
lbf). (A column one square inch in cross-section would have a weight of about 14.7 lbs, or about 65.4 N.).