Analysis of methods for estimating vapor pressure deficits and relative humidity

Vapor pressure deficit (VPD) is one of the critical variables that drives evapotranspiration (ET), and is of fundamental importance in crop models. The objectives of this work were to compare the methods used to calculate VPD, and to propose several different ways of calculating VPD at daily and diurnal time scales depending on the available data. The new estimation methods for VPD and relative humidity were tested and gave good results. Since these methods are not site specific, estimates of VPD can be used in several evapotranspiration estimation equations in order to estimate regional evapotranspiration patterns where only temperature, precipitation and insolation measurements are available.