What is defined as the mass of water vapor in the air?

• A. Absolute Humidity
• B. Relative Humidity
• C. Specific Humidity
• D. Dew Point

Answer: (A)

Absolute humidity is defined as the mass of water vapor present in a given volume of air, typically expressed in grams of water vapor per cubic meter of air. This measurement provides an indication of the actual amount of moisture in the air, irrespective of temperature or pressure conditions.

In contrast, relative humidity compares the current amount of water vapor in the air to the maximum amount that the air can hold at a specific temperature, expressed as a percentage. Specific humidity, on the other hand, indicates the mass of water vapor relative to the total mass of the air, which includes both the water vapor and the dry air. The dew point refers to the temperature at which air becomes saturated with moisture and water vapor begins to condense into liquid. Therefore, absolute humidity specifically focuses on the mass of water vapor alone, making it the correct choice in this context.