Air pressure is the force exerted on you by the weight of tiny particles of air (air molecules) although air molecules are invisible; they still have weight and take up space. Since there is a lot of "empty" space between air molecules, air can be compressed to fit in a smaller volume. When it is compressed, air is said to be "under high pressure". Air at sea level is what we are used to. Actually, we're so used to it that we forget we're actually feeling air pressure all the time! Weather forecasters measure air pressure with a barometer. Barometers are used to measure the current air pressure at a particular location in "inches of mercury" or in "millibars" (mb). A measurement of 29.92 inches of mercury is equivalent to 1013.25 millibars.
How much pressure are you under? Earth's atmosphere is pressing against each square inch of you with a force of 1 kilogram per square centimeter (14.7 pounds per square inch). The force on 1,000 square centimeters (a little larger than a square foot) is about a ton! Why doesn't all that pressure squash me? Remember that you have air inside your body too, that air balances out the pressure outside so you stay firm and not squishy. If the pressure is increased or decreased too much, we perish. Air pressure is also known as atmospheric pressure. Atmospheric pressure is measured using a barometer hence the word barometric pressure. It is basically a measure of the atmospheric pressure in the air.
It is measured in terms of the downward force that the atmosphere exerts per unit of a certain area. This reading is often taken by a barometer. Barometers differ in design and in precise functionality, but they all serve the centralized function of providing a reading of barometric pressure. The standard atmospheric pressure, or average pressure around sea level, is estimated to be 101.325 kPa, which is also known as 1 atm, or 1 atmosphere of pressure.
It varies with weather patterns and geography. Higher elevations have lesser atmospheric pressure because they simply have less atmosphere above them. In lower elevations, of course, the opposite is true. Its function within the world is important because if it did not exist, then the atmosphere wouldn't either. If the gases within the atmosphere weren't acted upon by the force of gravity, then there would be nothing to keep them from dissipating, leaving the earth uninhabitable for life forms. Of course, meteorologists also use barometric pressure to predict weather patterns and other scientists and researches use it to help in various scientific calculations.
One easy way for the layperson to observe the forces exerted by atmospheric pressure is the act of boiling water. Boiling water at a low elevation is much easier than at a high elevation. At sea level, distilled water boils at 212 degrees F. Higher temperatures are required above sea level and lower ones below it. This is because the downward force of barometric pressure is part of what causes water to boil. The less pressure there is, the more heat energy is required.
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This article touched the basics of the topic. I have 2 more resources related to the above. They are air pressure and barometric pressure . Do consider reading them.
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