|the mass of water vapour in a sample of moist air divided by the mass of the sample|
mass of water vapour in a unit mass of moist air, usually expressed as grams of vapour per kilogram of air, or, in air conditioning, as grains per pound. The specific humidity is an extremely useful quantity in meteorology. For example, the rate of evaporation of water from any surface is directly proportional to the specific humidity difference between the surface and the adjoining air
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