Atmospheric pressure

File:Plastic bottle at 14000 feet, 9000 feet and 1000 feet, sealed at 14000 feet.png

This plastic bottle was sealed at approximately 14,000 feet altitude, and was crushed by the increase in atmospheric pressure (at 9,000 feet and 1,000 feet) as it was brought down towards sea level.

Atmospheric pressure is a force in an area pushing against a surface by the weight of the atmosphere of Earth, a layer of air. The air is not distributed evenly around the globe. It moves, and at different times, the layer of air is thicker in some places than in others. Where the layer of air is thicker, there is more air. Since there is more air, there is a higher pressure in that spot. Where the layer of air is thinner, there is a lower atmospheric pressure.

At higher altitude, the atmospheric density and pressure are lower. This is because high places do not have as much air above them, pushing down.

Barometers can be used to measure atmospheric pressure for meteorology. There is the same atmospheric pressure from all directions. The SI unit for pressure is hPa. Other units such as bar and torr are used for various applications.

Atmospheric Pressure Media

• Day5pressureforecast.png

  Map showing atmospheric pressure in mbar or hPa

• Mslp-jja-djf.png

  15-year average mean sea-level pressure for June, July, and August (top) and December, January, and February (bottom). ERA-15 re-analysis.

• Aircraft altimeter.JPG

  Kollsman-type barometric aircraft altimeter.

• Storm over Snæfellsjökull.jpg

  Cloud formation above Snæfellsjökull (Iceland), formed above the mountain by orographic lift

• Atmospheric Pressure vs. Altitude.png

  Variation in atmospheric pressure with altitude, computed for 15 °C and 0% relative humidity.

• Wilma 2005-10-19 1315Z.jpg

  Hurricane Wilma on 19 October 2005. The pressure in the eye of the storm was 882 hPa (12.79 psi) at the time the image was taken.

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  Boling water in colour

Other websites

• Atmospheric pressure Citizendium