METEOROLOGY – HUMIDITY & WATER VAPOUR CALCULATOR Specific Humidity A precise tool.
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What is the Specific Humidity & How does it work?
Specific humidity is the ratio of the mass of water vapor to the total mass of air, expressed as a fraction (kg/kg). It represents the amount of moisture present in the air relative to its total mass.
q = frac{0.622 times e}{P – 0.378 times e}
q = specific humidity (kg/kg)
e = water vapor pressure (Pa)
P = total air pressure (Pa)
The water vapor pressure can be calculated from the relative humidity (RH) and the saturation vapor pressure at a given temperature. The specific humidity is then derived using the above formula.
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Frequently Asked Questions
What is specific humidity?
Specific humidity is the ratio of the mass of water vapor to the total mass of air, expressed as a fraction (kg/kg).
How do I calculate specific humidity?
Use the formula q = 0.622 * e / (P – 0.378 * e), where q is specific humidity, e is water vapor pressure, and P is total air pressure.
What units are used for specific humidity?
Specific humidity is expressed in kilograms per kilogram (kg/kg).
How does relative humidity relate to specific humidity?
Relative humidity can be used to calculate water vapor pressure, which is then used to find specific humidity.
Why is specific humidity important in meteorology?
Specific humidity helps meteorologists understand the moisture content of air and its impact on weather patterns.
Can specific humidity be greater than 1?
No, specific humidity cannot exceed 1 because it represents a fraction of water vapor to total air mass.
What is the difference between specific humidity and relative humidity?
Specific humidity measures the actual mass of water vapor in air, while relative humidity compares the current moisture level to the maximum possible at that temperature.

Results are for informational purposes only and do not constitute professional advice.