Atmospheric pressure can be defined as the pressure exerted by the atmosphere on the Earth, however, the most technical and correct way to define atmospheric pressure is to say that it is the weight of a column of air that extends from the Earth’s surface to the highest limit of the atmosphere.
The density of air decreases as the height rises, so atmospheric pressure is lower in the highest places on the planet.
On the other hand, it is also influenced by climate, so it is not simple to make a correct calculation of what the atmospheric pressure is at a specific point on the earth’s surface.
Points that have the same atmospheric pressure, measured in bars, come together to form an isobar. The graphical representation of these isobars are the common television and press maps to represent the meteorology of the weather.
Torricelli and Pascal
The calculation of it has aroused the interest of man for centuries, but it was in the 17th century that the method to perform these calculations correctly was discovered . The author of this achievement was the Italian scientist Evangelista Torricello, who in 1643 carried out an experiment that forever changed what was known about the subject.
Torricelli invented the barometer, an instrument built through a crystal tube with mercury in its interior, which makes it possible to observe for the first time the weight of air on Earth.
However, the definitive inflection point would be the work of Blaise Pascal, who drew on Torricelli’s previous studies and was able to go beyond his demonstrations.
Pascal took the barometer to different altitudes to prove that it was really the weight of the air that influenced the movement of mercury inside the tube. When he observed that on top of mountains the level of mercury was much higher than at the bottom of the mountain, he thus laid the foundation for all the studies that subsequently emerged of atmospheric pressure.
Anticyclones and depressions
The calculation of atmospheric pressure has numerous applications, the most commonly known being the possibility of making accurate weather forecasts. When talking about anticyclones or depressions it is referring to the increase in atmospheric pressure in the foreground and its decrease by around 1013 millibars in the background.