Which instrument is used to measure atmospheric pressure?

The barometer is the instrument specifically designed to measure atmospheric pressure. This measurement is crucial in meteorology and assists in forecasting weather conditions. By measuring the pressure exerted by the atmosphere, a barometer can indicate changes in weather patterns. For instance, falling atmospheric pressure often signals that a storm or inclement weather is approaching, while rising pressure usually indicates fair weather.

The other instruments mentioned have different functions: thermometers measure temperature, anemometers gauge wind speed, and hydrometers are used to determine the specific gravity or density of liquids, which is unrelated to atmospheric pressure. Understanding the specific purpose of each instrument reinforces the role of the barometer in weather observation.