Dew point temperature: Tdp [°C]
It is the temperature detectable for a given state of wet air at saturation for specific absolute humidity x. In the h-x diagram we draw a vertical line along a constant absolute humidity (x = constant) down to the saturation curve (RH = 100%) and at this point the isotherm at the intersection indicates the dew point temperature Tdp. For Tdp < 0°C it is needed to consider as a Frost Point Temperature, Tfp. The frost point is usually lower than the dew point, because the temperature required for ice to form is slightly lower than that required for water to condense.
