Absolute humidity

Absolute Humidity is a measure of the total amount of water vapor present in a given volume of air. It is expressed in terms of weight (grams) per cubic meter of air (g/m³). Unlike relative humidity, which expresses the amount of moisture in the air as a percentage of the maximum amount that could be held at the current temperature, absolute humidity is a direct measure of the amount of moisture in the air, regardless of temperature.

Definition

Absolute humidity is defined as the mass of water vapor divided by the volume of the air parcel. This can be expressed mathematically as:

AH = m / V

where:

• AH is the absolute humidity,
• m is the mass of the water vapor, and
• V is the volume of the air parcel.

Measurement

Measurement of absolute humidity is typically done using a hygrometer, a device that measures the amount of moisture in the air. There are several types of hygrometers, including hair hygrometers, dew point hygrometers, and psychrometers.

Factors Affecting Absolute Humidity

The absolute humidity of an air parcel can change as a result of several factors, including changes in temperature, pressure, or the addition or removal of moisture. For example, if the temperature of an air parcel increases, its volume will also increase, resulting in a decrease in absolute humidity, assuming no additional moisture is added.

Applications

Understanding absolute humidity is important in a variety of fields, including meteorology, climatology, agriculture, and building science. For example, in meteorology, absolute humidity is used to understand and predict weather patterns. In agriculture, it can help determine the optimal conditions for crop growth. In building science, understanding absolute humidity can help in the design of HVAC systems and in the prevention of mold growth.

See Also

• Relative Humidity
• Dew Point
• Hygrometer
• Psychrometer