What does a barometer measure?

A barometer is an instrument specifically designed to measure air pressure in the atmosphere. Air pressure is the force exerted by the weight of air molecules above a given point, and it plays a critical role in weather forecasting and understanding atmospheric conditions. As air pressure changes, it can indicate shifts in weather patterns—such as approaching storms or clear skies.

When a barometer measures an increase in air pressure, it often suggests fair weather, while a decrease may indicate that a storm or precipitation is likely. The relationship between air pressure and weather is a fundamental concept in meteorology, making the barometer an essential tool for weather analysis.

The other choices, while related to meteorology, do not pertain specifically to what a barometer measures. Humidity levels are measured using a hygrometer, temperature is gauged by a thermometer, and elevation can be determined using altimeters or GPS technology, but none of these instruments measure air pressure directly as a barometer does.