Definition - What does Atmospheric Pressure mean?
Atmospheric Pressure is the pressure exerted by the weight of air in the earth’s atmosphere. In most cases, the pressure can be approximated closely by hydrostatic pressure caused by weight of the air above the measurement point. In the case of molecules, if the numbers of the air molecules increase above the surface, many molecules exert force on the surface and as a result, the pressure increases. The reduction of the air molecules above the surface will decrease the pressure. Atmospheric Pressure can be measured by an instrument known as a barometer.
Petropedia explains Atmospheric Pressure
Air present in the environment has weight that presses everything it touches. This pressure is known as Atmospheric Pressure. It is a force applied on any surface by air above it as the gravity pulls it to the Earth. A barometer is used to measure the pressure. The barometer has a column of mercury in glass tube which falls or rises as the pressure of the atmosphere changes. This pressure decreases with an increase in altitude. When the pressure decreases, the available oxygen amount for breathing also decreases. At areas with very high altitudes, the pressure and oxygen amount decreases to an extent that people become sick and sometimes even die.
The Atmospheric Pressure is also considered as an indicator of the weather. When low-pressure system travels to an area, it results in wind, cloudiness and precipitation. The area with high-pressure will have calm and fair weather.