Saturation Vapor Pressure
Given T in Kelvin these equations will give es in milliBar.from Fleagle and Businger, Vol.5, pg. 62 (QC880.F59)
The first law can be written as
2 - 1)where
1 
1/
1 and index 1 refers to the liquid
phase and index 2 refers to the gas phase.
For an isothermal change of phase, the Clausius-Clapeyron
equation has the form
2-1)]Water vapor behaves like an ideal gas and
2 
1
for a change in state.
2.5 · 103 Joules/gm 2.824 · 103 Joules/gm over ice2 · Rw T2-1)] 
(L · 2)/T = (L · Ps) /(Rw · T2)
(L/Rw) · (dT/T2) =
-(L/Rw)|T->T0 + C =
-L/(Rw · T0) + L/(Rw· T) + Cat triple point all 3 phases can exist in equilibrium, 0.0098° C and Ps = 6.11 mB
Undocumented fit is used in the program watsat.F (over liquid)
Note this is the same equation as above, except that it assumes L = 2485.2 Joules/gm and T0 = 273.15 ° K
Another undocumented fit is given (but not used) in the program watsat.F
| coef | over ice | over water |
| a | -5631.1206 | -2313.0338 |
| b | -8.363602 | -164.03307 |
| c | 8.2312 | 38.053682 |
| d | -3.861449 · 10-2 | -1.3844344 · 10-1 |
| e | 2.77494 · 10-5 | 7.4465367 · 10-5 |
From Rogers and Yau, pg. 16
| coef | Rogers & Yau over water |
| a | 17.67 |
| b | 29.66 |
Murray, F.W. 1966. ``On the computation of Saturation
Vapor Pressure'' J. Appl. Meteor. 6 p.204
| coef | Murray over ice | Murray over water |
| a | 21.8745584 | 17.2693882 |
| b | 7.66 | 35.86 |
Saucier, W.J. 1883. ``Principles of Meteorological Analysis'' Dover pg. 9 who uses values of Tetens (1930). Note, he used 10[(a'T)/(T-b')] with T in Centigrade so to convert into the form above a = log 10 · a' and b = 273.16-b'.
| coef | over ice | over water |
| a | 21.875 | 17.27 |
| b | 7.66 | 35.86 |
