<P> There are several different constant sets in use . The ones used in NOAA's presentation are taken from a 1980 paper by David Bolton in the Monthly Weather Review: </P> <Dl> <Dd> a = 6.112 mb, b = 17.67, c = 243.5 ° C . </Dd> </Dl> <Dd> a = 6.112 mb, b = 17.67, c = 243.5 ° C . </Dd> <P> These valuations provide a maximum error of 0.1%, for − 30 ° C ≤ T ≤ 35 ° C and 1% <RH <100% . Also noteworthy is the Sonntag1990, </P>

As the difference between the dewpoint and the ambient air temperature decreases