Which instrument is primarily used to measure atmospheric pressure during surface observations?

The instrument that is primarily used to measure atmospheric pressure during surface observations is the barometer. Barometers are designed specifically to detect changes in air pressure and are essential for weather forecasting and understanding atmospheric conditions.

The functioning of a barometer is based on the principle that atmospheric pressure will exert force on a column of liquid within a tube or a specialized digital mechanism. When atmospheric pressure increases, it pushes the liquid higher, and when it decreases, the level drops. This measurement is crucial for meteorologists to predict weather patterns since changes in atmospheric pressure can indicate approaching weather systems, such as storms or high-pressure areas that contribute to fair weather.

In contrast, instruments like anemometers are used to measure wind speed, thermometers measure air temperature, and snow gauges are employed to measure snowfall. These instruments are essential for gathering comprehensive weather data, but none are designed for measuring atmospheric pressure, which defines why the barometer is the correct choice for this specific task.