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.

Enhancement factor (EF)
°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

  1. Buck 1981

References

External links