Calculating The Dew Point
See also: Psychrometric chartA well-known approximation used to calculate the dew point, Tdp, given just the actual ("dry bulb") air temperature, T and relative humidity (in percent), RH, is the Magnus formula:
The more complete formulation and origin of this approximation involves the interrelated saturated water vapor pressure (in units of millibar, which is also hPa) at T, Ps(T), and the actual water vapor pressure (also in units of millibar), Pa(T), which can be either found with RH or approximated with the barometric pressure (in millibar units), BPmb, and "wet-bulb" temperature, Tw is:
For greater accuracy, Ps(T) (and, therefore, γ(T,RH)) can be enhanced, using part of the Bögel modification, also known as the Arden Buck equation, which adds a fourth, d constant:
-
-
- (where )
-
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:
These valuations provide a minimum accuracy of 0.1%, for
-
-
-
-
- -30°C ≤ T ≤ +35°C;
- 1% < RH < 100%;
- -30°C ≤ T ≤ +35°C;
-
-
-
Also noteworthy is the Sonntag1990,
Another common set of values originates from the 1974 Psychrometry and Psychrometric Charts, as presented by Paroscientific,
Also, in the Journal of Applied Meteorology and Climatology, Arden Buck presents several different valuation sets, with different minimum accuracies for different temperature ranges. Two particular sets provide a range of -40°C → +50°C between the two, with even greater minimum accuracy than all of the other, above sets (maximum error at given |C°| extreme):
Read more about this topic: Dew Point
Famous quotes containing the words calculating the, calculating, dew and/or point:
“What our children have to fear is not the cars on the highways of tomorrow but our own pleasure in calculating the most elegant parameters of their deaths.”
—J.G. (James Graham)
“Sin in this country has been always said to be rather calculating than impulsive.”
—Frank Moore Colby (18651925)
“In the morn and liquid dew of youth
Contagious blastments are most imminent.”
—William Shakespeare (15641616)
“Film is more than the twentieth-century art. Its another part of the twentieth-century mind. Its the world seen from inside. Weve come to a certain point in the history of film. If a thing can be filmed, the film is implied in the thing itself. This is where we are. The twentieth century is on film.... You have to ask yourself if theres anything about us more important than the fact that were constantly on film, constantly watching ourselves.”
—Don Delillo (b. 1926)