Procedures to Develop a Standardized Reference Evapotranspiration Zone Map

Abstract

The goal of this study was to define procedures needed to make a Standardized Reference Evapotranspiration (ETos) zone map using daily climate data from full stations, having solar radiation, air temperature, wind speed, relative humidity, and from partial stations, having only temperature data. For partial stations, the ETos was estimated either by substitution of data from nearby full stations or by using a calibration factor and the Hargreaves–Samani equation estimate of reference evapotranspiration. The substitution method gave statistically better estimates of ETos than the calibration method. In addition, to improve the number and distribution of ETos estimates, three interpolation techniques were evaluated. Ordinary kriging provided better spatialization of ETos data than the inverse distance weighting and radial basis function.