Barometer is a device that is used for measuring the atmospheric pressure. It uses water, air, or mercury to measure the atmospheric pressure. Through barometer the meteorologists can forecast a short term change in the weather. This process of weather forecast with the help of barometer is not that easy as it undergoes numerous weather analyses.

The depiction of atmospheric pressure is very important. If the atmospheric pressure falls, it causes storms and heavy rains. There are three types of barometers that work differently to detect the atmospheric pressure such as:

• Water-based barometers: The device is known as Goethe thermometer. The sealed body of the container is half filled with water. There is also a narrow spout which is connected to the sealed body in such a way that it lies below the water level of the container and raises above the water level the place which is open to the atmosphere. When there is a low pressure the water level in the spout gradually raises above the water level of the body and when the pressure is higher the water level of the spout falls.

Mercury barometers: This Weather instrument is made of a glass column of about 76 cm tall. It is closed at one end. The base of the container has an open reservoir filled with mercury. High pressure raises the level of the mercury and when there is a low pressure the mercury level eventually falls.

Aneroid barometers: These barometers have a small metal box known as aneroid capsule. The box is tightly sealed so that the change in air pressure outside the box causes an expansion and contraction of the box.