A barometer is a meteorological instrument that measures air pressure in the atmosphere. Learn about the history, types, and functions of barometers, and how they are used to determine weather conditions and altitude. Barometers are essential scientific instruments used to measure air pressure, which is the force exerted by the atmosphere on objects at or near the Earth’s surface. Air pressure plays a critical role in weather forecasting, aviation, and meteorology in general. A mercury barometer is an instrument used to measure atmospheric pressure in a certain location and has a vertical glass tube closed at the top sitting in an open mercury-filled basin at the bottom. A barometer is a scientific instrument used to measure atmospheric pressure, also called barometric pressure. The atmosphere is the layers of air wrapped around Earth. That air has a weight and presses against everything it touches as gravity pulls it to Earth. Barometers measure this pressure. Atmospheric pressure is an indicator of weather. Changes in the atmosphere, including changes in air pressure, affect the weather. Meteorologists use barometers to predict short-term changes in the ...
