From Glossary of Meteorology
An analytic expression for saturation vapor pressure, es , given as a function of temperature by
where the temperature T is given in °C and the vapor pressure is in kPa.
A slightly improved version is shown under Clausius–Clapeyron equation.
Tetens, O. 1930. Uber einige meteorologische Begriffe. Z. Geophys.. 6. 297–309.
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