Barometric Pressure

Barometer

Barometric pressure, essentially, is the measure of how much air is on top of a particular location at any given time. High pressure suggests cooler conditions aloft, allowing for a denser concentration of molecules and thus a heavier column on top of a particular location. High pressure generally means more stable air, as the heavier column suppresses rising air, while low pressure is indicative of unstable air, as the atmosphere attempts to achieve equilibrium, air rushes into the column and generates rising air.
Barometric pressure is measured by barometers, as pictured above. The units of measurement are either inches of mercury (inHG) or millibars (mb). Inches of mercury is commonly seen on news reports and generally falls in the 28-32 range, with 29.92inHG the accepted “standard air pressure”. It was orginally based upon how high mercury would rise in a column in response to pressure exerted elsewhere in the apparatus. More commonly used in the international community as well as by non television meteorologists is the metric millibar, where standard pressure is approximately 1013mb.

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