Relative humidity

Relative humidity (RH) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. Relative humidity depends on temperature and the pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air. A related parameter is that of dew point. Relative humidity (RH) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. Relative humidity depends on temperature and the pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air. A related parameter is that of dew point. The relative humidity ( R H {displaystyle (RH} or ϕ ) {displaystyle phi )} of an air–water mixture is defined as the ratio of the partial pressure of water vapor ( p H 2 O ) {displaystyle (p_{mathrm {H_{2}O} })} in the mixture to the equilibrium vapor pressure of water ( p H 2 O ∗ ) {displaystyle (p_{mathrm {H_{2}O} }^{*})} over a flat surface of pure water at a given temperature: Relative humidity is normally expressed as a percentage; a higher percentage means that the air–water mixture is more humid. At 100% relative humidity, the air is saturated and is at its dewpoint.