Which meteorological instrument is specifically used for measuring the atmospheric air pressure at a place?

Introduction / Context:
This question is from basic meteorology and physics and asks about instruments used to measure different atmospheric quantities. Weather stations and laboratories use special devices to track air pressure, temperature, humidity and wind speed. Knowing which instrument corresponds to air pressure helps you interpret weather reports and understand how meteorologists predict weather changes.

Given Data / Assumptions:

• We want the name of the instrument that measures atmospheric air pressure.
• Options include anemometer, barometer, hygrometer and thermometer.
• We assume standard meteorological instruments.

Concept / Approach:
A barometer is the instrument used to measure atmospheric pressure. It may be a mercury barometer, an aneroid barometer or a digital pressure sensor, but the general name remains barometer. An anemometer measures wind speed, a hygrometer measures humidity and a thermometer measures temperature. Therefore, the correct instrument for air pressure is the barometer.

Step-by-Step Solution:
Step 1: Recall that air pressure is the force exerted by the weight of the air column per unit area on the Earth surface. Step 2: Recognise that barometers were historically invented to measure this pressure using mercury columns. Step 3: Modern barometers include aneroid barometers and electronic barometric sensors, but they still retain the same name. Step 4: Anemometers, by contrast, are designed with cups or vanes to measure wind speed, not pressure. Step 5: Hygrometers use materials that respond to moisture to measure relative humidity, not pressure. Step 6: Thermometers measure temperature using thermometric substances or electronic sensors, not air pressure. Step 7: Thus, the correct instrument for measuring atmospheric pressure is the barometer.

Verification / Alternative check:
Weather reports often show barometric pressure readings in units such as millibar or hectopascal. Devices at home or in smartphones that display atmospheric pressure are often called barometers or barometric sensors. The word baro comes from a Greek root meaning weight, reflecting that the instrument measures the weight of the air column. This consistent naming across devices confirms that barometer is the correct instrument name for air pressure measurements.

Why Other Options Are Wrong:
Anemometer is used for measuring wind speed, often displayed in km/h or m/s, not pressure. Hygrometer is designed to measure humidity or moisture content in the air, not the pressure. Thermometer is used for measuring temperature, usually in degree Celsius or kelvin, not air pressure.

Common Pitfalls:
Because all the options are meteorological instruments, students sometimes confuse their functions. A useful memory aid is to associate barometer with barometric pressure charts, anemometer with moving arms or cups that spin in the wind, hygrometer with hygro meaning moisture and thermometer with thermo meaning heat. Keeping these associations clear will help you answer instrument questions quickly and accurately in exams.

Final Answer:
The instrument used to measure atmospheric air pressure is the Barometer.