Saturation Ps and Partial Water Vapour Pressure Pd

The original Wexler s equation published in 1971 [8] has been revised in 1976 [9], and updated in 1998 with coefficients computed for the International Temperature Scale of 1990 (lTS-90) [10]. This updated version of Wexler s equation has been used to calculate the saturation water vapour pressure Ps for each mean daily temperature, and also to calculate the partial water vapour pressure Pd at the same time point and place by taking the corresponding daily dewpoints instead of the temperature. 

Ps = Saturation vapour pressure [Pa] over water in the pure phase 

To obtain the mean values for Ps and Pd per year, the yearly mean values for temperatures and dewpoints calculated as described above have been used, respectively. 

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