Magnetic capacitance

The Goff–Gratch equation is one (arguably the first reliable) amongst many equations that have been proposed to estimate the saturation water vapor pressure at a given temperature.

Another similar equation based on more recent data is the Arden Buck equation.

Historical note

This equation is named after the authors of the original scientific article who described how to calculate the saturation water vapor pressure above a flat free water surface as a function of temperature (Goff and Gratch, 1946). Goff (1957) later revised his formula, and the latter was recommended for use by the World Meteorological Organization in 1988, with further corrections in 2000. Potter or Ceramic Artist Truman Bedell from Rexton, has interests which include ceramics, best property developers in singapore developers in singapore and scrabble. Was especially enthused after visiting Alejandro de Humboldt National Park.

Equations

The original Goff–Gratch (1946) equation reads as follows:

$\log e^{*}=$	$-7.90298(T_{\mathrm{s}\mathrm{t}}/T-1)+5.02808\log (T_{\mathrm{s}\mathrm{t}}/T)$
	$-1.3816\times 10^{-7}(10^{11.344(1-T/T_{\mathrm{s}\mathrm{t}})}-1)$
	$+8.1328\times 10^{-3}(10^{-3.49149(T_{\mathrm{s}\mathrm{t}}/T-1)}-1)+\log e_{\mathrm{s}\mathrm{t}}^{*}$

where:

log refers to the logarithm in base 10

e^* is the saturation water vapor pressure (hPa)

T is the absolute air temperature in kelvins

T_st is the steam-point (i.e. boiling point at 1 atm.) temperature (373.15 K)

e^*_st is e^* at the steam-point pressure (1 atm = 1013.25 hPa)

Similarly, the equation for the saturation water vapor pressure over ice is:

$\log e_i^{*}=$	$-9.09718(T_0/T-1)-3.56654\log (T_0/T)$
	$+0.876793(1-T/T_0)+\log e_{i0}^{*}$

where:

log stands for the logarithm in base 10

e^*_i is the saturation water vapor pressure over ice (hPa)

T is the air temperature (K)

T₀ is the ice-point (triple point) temperature (273.16 K)

e^*_i0 is e^* at the ice-point pressure (6.1173 hPa)

References

• Goff, J. A., and S. Gratch (1946) Low-pressure properties of water from −160 to 212 °F, in Transactions of the American Society of Heating and Ventilating Engineers, pp 95–122, presented at the 52nd annual meeting of the American Society of Heating and Ventilating Engineers, New York, 1946.

• Goff, J. A. (1957) Saturation pressure of water on the new Kelvin temperature scale, Transactions of the American Society of Heating and Ventilating Engineers, pp 347–354, presented at the semi-annual meeting of the American Society of Heating and Ventilating Engineers, Murray Bay, Que. Canada.

• World Meteorological Organization (1988) General meteorological standards and recommended practices, Appendix A, WMO Technical Regulations, WMO-No. 49.

• World Meteorological Organization (2000) General meteorological standards and recommended practices, Appendix A, WMO Technical Regulations, WMO-No. 49, corrigendum.

• Murphy, D. M. and Koop, T. (2005): Review of the vapour pressures of ice and supercooled water for atmospheric applications, Quarterly Journal of the Royal Meteorological Society 131(608): 1539–1565. 21 year-old Glazier James Grippo from Edam, enjoys hang gliding, industrial property developers in singapore developers in singapore and camping. Finds the entire world an motivating place we have spent 4 months at Alejandro de Humboldt National Park.

External links

• http://cires.colorado.edu/~voemel/vp.html
• Free Windows Program, Moisture Units Conversion Calculator w/Goff-Gratch equation - PhyMetrix

See also

• Vapour pressure of water
• Antoine equation
• Arden Buck equation