absolute humidity

The weight of water vapour per unit volume of air, which determines the temperature of the dew point. The maximum absolute humidity increases with temperature, approximately doubling with every 10oC rise. However, saturated air is less dense than dry air because the molecular weight of water is less than that of the main atmospheric gases nitrogen and oxygen.

This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
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