### 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 Pt = 611.657 ± 0.01 Pa at temperature Tt = 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)
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