Atmospheric pressure

Atmospheric pressure (air pressure or barometric pressure - after the barometer) is the pressure within the Earth's atmosphere, i.e., the force per unit area exerted against a surface by the air column's weight above that surface within its atmosphere.

etm: Gr atmos ('vapor' or 'steam') + sphaira ('sphere') + Latin pressura ('action to press')

The standard reference of atmospheric pressure (1 atm) is 101,33 Pa = 101.33 kPa = 101.33kPa/100 = 1013.3 bar.

[2] A value of 29.92 inHg (inches of mercury) or 14.6 PSI is used to determine the average-day sea level pressures. Any value below 29.92 inHg would be considered low pressure and anything above would be high pressure.

[1] 30-year (1991–2020) mean sea level pressure based on ERA5 reanalysis data

This Mean Sea Level Pressure (MSLP) map shows the lowest pressure region the ocean ring surrounding Antarctica, called the Circumpolar Trough.

The map normalizes atmospheric pressure across the globe to sea level. Around the Antarctic coast/Southern Ocean, intense low-pressure storm systems constantly circle the continent, creating the dark blue/purple band of low sea-level pressure (below 980 hPa). Over the interior of Antarctica (the South Pole), extremely cold, dense air sinks, creating a high-pressure zone relative to sea level.

Behavior

Gravity and density: Earth's gravitational pull holds air molecules close to the surface, creating max air density and pressure at sea level.
Altitude relationship: Rising altitude reduces the atmospheric pressure exponentially as the overlying air column's total mass is reduced.
Temperature influence: Heating air causes it to expand and become less dense, lowering local surface pressure, whereas cooling air increases density and surface pressure.

History

1643 - Italian physicist Evangelista Torricelli invented the mercury barometer, demonstrating that atmospheric pressure supports a 760 mm column of mercury.
1648: Blaise Pascal proved that atmospheric pressure decreases with altitude by conducting measurements at different elevations on the Puy de Dôme in France.

Components

Pressure tendency is the

References

[1] Wikipedia
[2] Barometric Pressure and Fishing | Learn with Landers - Landers Fishin (YouTube)
[3]
[4]

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Atmospheric pressure

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