Water Vapor - JPL paper

In my research on water vapor, I came across a paper from JPL prepared for the Air Force with funding from NASA.

Atmospheric Noise Temperature Induced by Clouds and Other Weather Phenomena at SHF Band (1-45 GHz)
Christian Ho, Stephen Slobin, and Kelly Gritton, August 11, 2005

It is not my intent to review the paper. However, on page 18, values of saturation water vapor are provided without a source. This caught my eye.

6.108 mbar at 0°C

Most references are very specific - the standard is defined at 0.01°C, not 0.00°C. For instance, according to Review of the vapour pressures of ice and supercooled water for atmospheric applications by D. M. Murphy and T. Koop, 29 Dec 2006

The vapour pressure of both ice and liquid water at the triple point is
P_t = 611.657 ± 0.01 Pa at temperature T_t = 273.16 K
(Guildner et al. 1976, Vapor pressure of water at its triple point. J. Res. Natl. Bur. Stand., 80A, 505–521)

Different temperatures, different partial pressures, confused reader.

At any rate, I tried to determine which set of formulas the paper's authors used to compute their examples .. of the 17 models I implemented in my software, their numbers almost match WMO_Goff.

Comparison of saturation partial pressures - Water Vapor over liquid water
Formula	Partial Pressure at Saturation (mbar)
Formula	0°C	10°C	15°C	20°C	30°C	40°C
JPL Paper - p18	6.108	12.27	17.04	23.37	42.43	73.78
GoffGratch	6.10336	12.26406	17.03281	23.35847	42.40599	73.73810
CIMO	6.11200	12.26030	17.01672	23.32596	42.33724	73.67458
HylandWexler	6.11213	12.27995	17.05448	23.38804	42.46030	73.83460
MagnusTetens	6.10336	12.27069	17.04131	23.36647	42.40202	73.70792
Buck_original	6.11210	12.27598	17.04571	23.37282	42.43509	73.84175
Buck_manual	6.11210	12.27860	17.05173	23.38340	42.45126	73.82360
WMO_Goff	6.10695	12.27089	17.04204	23.37080	42.42726	73.77329	This appears to be the best match
WMO2000	6.10696	12.26127	17.02177	23.33296	42.31740	73.49567
Wexler	6.08198	12.20949	16.94908	23.23254	42.13474	73.18493
Sonntag	6.11213	12.28133	17.05713	23.39249	42.47029	73.85296
Bolton	6.11200	12.27170	17.04049	23.36947	42.45575	73.94901
IAPWS	6.11213	12.28112	17.05677	23.39194	42.46920	73.85110
Preining	6.10299	12.26268	17.03013	23.35361	42.39296	73.71023
MurphyKoop	6.11213	12.28257	17.05880	23.39399	42.46814	73.84306
Seinfeld_Pandis	6.11216	12.27958	17.05247	23.38265	42.43982	73.78175
GISS_AR4	6.10358	12.29610	17.13726	23.61552	43.44388	76.86917

The data in the table was generated by a program - the grey boxes highlight values within 0.01 of the values in the JPL Paper, except that for the 0.00°C column, the range is +/- 0.002.

Author: Robert Clemenzi

Water Vapor - JPL paper

URL: http:// mc-computing.com / Science_Facts / Water_Vapor / JPL_paper.html