Earth:Arden Buck equation
From HandWiki
The Arden Buck equations are a group of empirical correlations that relate the saturation vapor pressure to temperature for moist air. The curve fits have been optimized for more accuracy than the Goff–Gratch equation in the range −80 to 50 °C (−112 to 122 °F).[1] A set of several equations were developed, each of which is applicable in a different situation.
Formula
The equations suggested by (Buck 1996) (which are modifications of the equations in (Buck 1981)) are:
- [math]\displaystyle{ P_{\mathrm{s}}\left(T \right) = 6.1121 \exp \left(\left( 18.678 - \frac{T} {234.5}\right)\left( \frac{T} {257.14 + T} \right)\right) }[/math], over liquid water, T > 0 °C
- [math]\displaystyle{ P_{\mathrm{s}}\left(T \right) = 6.1115 \exp \left(\left( 23.036 - \frac{T} {333.7}\right)\left( \frac{T} {279.82 + T} \right)\right) }[/math], over ice, T < 0 °C
where:
- Ps(T) is the saturation vapor pressure in hPa
- exp(x) is the exponential function
- T is the air temperature in degrees Celsius
Buck (1981) also lists enhancement factors for a temperature range of −80 to 50 °C (−112 to 122 °F) at pressures of 1,000 mb, 500 mb, and 250 mb. These coefficients are listed in the table below.
| °C | 1.000 mb | 500 mb | 250 mb |
|---|---|---|---|
| -80 | 1,00410 | 1,00200 | |
| -70 | 1,00360 | 1,00180 | |
| -60 | 1,00640 | 1,00320 | 1,00160 |
| -50 | 1,00580 | 1,00290 | 1,00140 |
| -40 | 1,00520 | 1,00260 | 1,00130 |
| -30 | 1,00470 | 1,00240 | 1,00120 |
| -20 | 1,00440 | 1,00220 | 1,00120 |
| -10 | 1,00410 | 1,00220 | 1,00120 |
| 0 | 1,00395 | 1,00219 | 1,00132 |
| 10 | 1,00388 | 1,00229 | |
| 20 | 1,00400 | 1,00251 | |
| 30 | 1,00426 | 1,00284 | |
| 40 | 1,00467 | 1,00323 | |
| 50 | 1,00519 |
See also
Notes
- ↑ Buck 1981
References
- Buck, A. L. (1981), "New equations for computing vapor pressure and enhancement factor", J. Appl. Meteorol. 20 (12): 1527–1532, doi:10.1175/1520-0450(1981)020<1527:NEFCVP>2.0.CO;2, Bibcode: 1981JApMe..20.1527B, https://doi.org/10.1175/1520-0450(1981)020%3C1527:NEFCVP%3E2.0.CO;2
- Buck (1996), Buck Research CR-1A User's Manual, Appendix 1., http://www.hygrometers.com/wp-content/uploads/CR-1A-users-manual-2009-12.pdf
External links
- Web Page listing various vapor pressure equations (for below 0 °C)
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