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Atmospheric pressure varies due to natural currents and affects weather patterns. Air molecules are pulled towards the Earth’s surface by gravity, creating pressure. Barometric pressure can be measured with a barometer. Low pressure can cause severe weather, while high pressure results in clear weather. Temperature and humidity can also affect pressure.
Atmospheric pressure is the amount of force exerted on an area by all the air above that area. Natural variations, or currents, in the atmosphere cause the actual pressure at different points on the earth’s surface to vary. When atmospheric pressure is lower than normal, it is an indication that there are fewer air molecules above an area. If an area has higher than normal atmospheric pressure, then it indicates that there are more air molecules in the atmosphere above. The pressure in the atmosphere can affect the weather, allowing for storm formation and temperature fluctuations regardless of the seasons.
The air that makes up the Earth’s atmosphere is made up of different types of molecules. These molecules are like any other, except that they are not visible to the human eye and are in gaseous form. Earth’s gravity still acts on the molecules and pulls them towards the surface. This attraction of the air creates pressure on every surface of the Earth.
The further a person moves through the atmosphere, the lower the pressure becomes. This is because, as an object moves up, the amount of air molecules above it decreases because the distance between the object and the edge of the atmosphere is shorter. Similarly, if an object is brought below the surface of the Earth, below sea level, the pressure the object is experiencing will start to increase, because more air will be above it.
Barometric pressure can be measured with a device known as a barometer. A common form of barometer uses liquid mercury in a U-shaped tube. If there are changes in pressure, the mercury inside the glass will react and move towards or away from an opening in the glass. The result is that mercury will rise or fall to indicate a change. Another type of barometer uses a sealed glass capsule that expands or contracts as the external pressure changes.
Weather patterns across the planet are affected by atmospheric pressure, and the weather itself can affect pressure as well. Tornadoes and other severe cyclonic disturbances are often centralized in an area of incredibly low pressure due to large-scale air movements. High-pressure areas, which have more mass than normal, cause clear, calm weather. The temperature in an area, as well as the humidity, can also affect pressure by expanding or contracting the air or by saturating it with tiny particles of water.
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