An improved method to estimate actual vapor pressure without relative humidity data

Estimating actual vapor pressure (ea) without relative humidity (RH) data continues to draw research attention. One of the accurate ways estimate ea is through estimation dew point temperature (Tdew) from minimum (Tmin) or mean (Tmean). Two existing methods have been largely used ea. The first method (method I) assumes that Tdew close Tmin. other one II) adjusts Tmin with piecewise correction factors (aT) sub-humid hyper arid regions, and Tmean a fixed factor, aD, in humid regions. Here, two are proposed III) dynamic aT based on correlation function between aridity index (AI) regardless climate zones. second IV) when AI < 1.00 aD ≥ 1.00. performance four was evaluated 886 meteorological stations distributed hyper-arid Results showed there significant logarithmic AI, but no AI. Daily values estimated by I were greatly overestimated semi-arid reasonably accuracy II improved dry regions decreased compared I. (III further produced reasonable daily III slightly better than IV. Similar results also observed for monthly Therefore, highly recommended RH unavailable.