2. Parameters

Moisture/Humidity » Relative Humidity (RH) Definition & Skew-T Procedure

Definition: Relative Humidity (RH)

Relative humidity (RH) is the ratio (expressed as a percent) of the amount of water vapor in a given volume of air to the amount that volume would hold if the air were saturated.

Skew-T procedure to determine relative humidity

Skew-T Procedure

The relative humidity can be computed from the mixing ratio (w) and the saturation mixing ratio (ws) by the following equation:

RH = 100 * (w/ws)

In the example sounding above, a parcel of air at 850 hPa has a mixing ratio of 3 g/kg, a saturation mixing ratio of 6.5 g/kg, and a relative humidity of 46%.

Note the definition assumes a saturation mixing ratio (and relative humidity) for liquid water, not ice.