What is a barometer used for?

A barometer is specifically designed to measure atmospheric pressure. This is crucial for various applications, including weather forecasting and understanding air pressure changes. By measuring the pressure of the atmosphere, a barometer can help predict weather patterns; for instance, a drop in atmospheric pressure often indicates that stormy weather is likely, while an increase can suggest fair weather.

The other options describe different instruments or functions. For instance, humidifiers and hygrometers are employed for measuring humidity, anemometers measure wind speed and force, and thermometers are used for measuring temperature. Each of these functions is distinct from that of a barometer, which focuses solely on atmospheric pressure.