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 . A set of several equations were developed, each of which is applicable in a different situation. Formula The equations suggested by (which are modifications of the equations in ) are: , over liquid water, > 0 °C , over ice, < 0 °C where: is the saturation vapor pressure in hPa is the exponential function 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. See also Vapour pressure of water Antoine equation Tetens equation Lee–Kesler method Goff–Gratch equation Notes References External links Web Page listing various vapor pressure equations (for below 0 °C) Atmospheric thermodynamics Psychrometrics