How is atmospheric pressure measured?

Atmospheric pressure is measured using a device called a barometer, which can be either mercury-based or aneroid.

A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. The concept of a barometer was developed in the 17th century by Evangelista Torricelli, an Italian physicist and mathematician. There are two main types of barometers: mercury barometers and aneroid barometers.

A mercury barometer consists of a glass tube, closed at one end, filled with mercury and inverted into a dish of mercury. The height of the mercury column is a direct indication of the atmospheric pressure. If the atmospheric pressure increases, it pushes more mercury up the tube, and if the pressure decreases, the mercury level in the tube drops. The height of the mercury is usually measured in millimetres or inches.

An aneroid barometer, on the other hand, uses a small, flexible metal box called an aneroid cell. This cell is sealed and partially evacuated. When the atmospheric pressure changes, the cell either expands or contracts. This movement is mechanically amplified to move a pointer across a scale, providing a pressure reading. Aneroid barometers are often used in portable instruments and are popular in homes and recreational boats.

Both types of barometers are used in weather forecasting. By tracking changes in atmospheric pressure, meteorologists can predict short-term changes in the weather. For example, a rapid drop in atmospheric pressure can indicate an approaching storm.

In summary, atmospheric pressure is measured using a barometer, either mercury-based or aneroid, which provides a direct indication of the pressure exerted by the atmosphere at a specific location and time.