RELATIVE HUMIDITY (RH)

Ratio that compares the amount of water vapor in the air to the saturation amount. The ratio of the mixing ratio of the ambient air and the saturation mixing ratio of the same air with the same pressure and temperature. Relative humidity is usually expressed as a percentage. When using relative humidity as an indication of absolute moisture quantity, caution must be used, because colder air has a smaller saturation mixing ratio than warmer air.