Which instrument is used to measure humidity (and what does it reveal about atmospheric conditions)?

Which instrument is used to measure humidity (and what does it reveal about atmospheric conditions)?

• A. Hygrometer (or psychrometer)
• B. Thermometer
• C. Barometer
• D. Rain gauge

Answer: (A)

Humidity is measured with a hygrometer, and sometimes a psychrometer is used as a specific type of hygrometer. This instrument reveals how much water vapor is in the air, usually reported as relative humidity. When relative humidity is high, the air is near saturation, which promotes dew, fog, and cloud formation and can make the air feel muggy because sweat evaporates more slowly. When it’s low, the air is dry, evaporation happens quickly, and conditions often feel cooler and drier. Related ideas like the dew point also come from humidity readings, indicating the temperature at which air becomes saturated. The other tools measure different things: a thermometer for temperature, a barometer for air pressure, and a rain gauge for precipitation, so they don’t directly tell us how moist the air is.

Humidity is measured with a hygrometer, and sometimes a psychrometer is used as a specific type of hygrometer. This instrument reveals how much water vapor is in the air, usually reported as relative humidity. When relative humidity is high, the air is near saturation, which promotes dew, fog, and cloud formation and can make the air feel muggy because sweat evaporates more slowly. When it’s low, the air is dry, evaporation happens quickly, and conditions often feel cooler and drier. Related ideas like the dew point also come from humidity readings, indicating the temperature at which air becomes saturated. The other tools measure different things: a thermometer for temperature, a barometer for air pressure, and a rain gauge for precipitation, so they don’t directly tell us how moist the air is.