Answer – The tool used to measure air pressure for weather information is a barometer.

Explanation: 

The atmosphere is the air that surrounds the Earth. As gravity pulls it downward, it exerts pressure, known as atmospheric pressure, on everything it is in contact with. 

When air temperature changes in a particular region, a corresponding change in atmospheric pressure is observed. This, in turn, results in wind and the development of pressure systems. The wind further transports the pressure systems, causing them to be altered as they move over land and water bodies at varying altitudes and depths. The changes in air pressure alongside other atmospheric conditions impact the weather at a given location.

A barometer is used to detect variations in air pressure and hence to predict short-term weather changes. It measures atmospheric pressure in atmospheres (atm) or bars. Different readings on a barometer can be interpreted for weather patterns as follows:

• A gradually climbing reading indicates improving weather.
• A gradually dropping reading indicates worsening weather.
• A sudden increase in atmospheric pressure suggests cool, pleasant weather.
• A sudden drop in atmospheric pressure suggests an impending storm.
• Stable atmospheric pressure means that the weather is likely to remain unchanged.

Barometers are usually one of two kinds: mercury or aneroid. When using a mercury barometer, atmospheric pressure change is measured by finding the increase/decrease in the height of its mercury column. An aneroid barometer, on the other hand, has no liquid; so while using it, atmospheric pressure change is observed from the expansion/contraction of its capsule’s flexible wall.

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