Ecology, Environment and Conservation Paper

Vol 27, Issue 1, 2021; Page No.(421-433)

ESTIMATION OF REFERENCE EVAPOTRANSPIRATION UNDER HYPER-ARID CLIMATES: TESTING SEVERAL VAPOR PRESSURE DEFICIT MODELS

Azel Almutairi

Abstract

The estimation of reference evapotranspiration, ETo , is profoundly important in water resources management. Avoiding all expensive methods, the FAO-56 Penman-Monteith method is recognized as the standard approach for estimating ETo, which requires daily meteorological data inputs such as vapor pressure deficit, VPD. In this study, thirteen VPD models are used to estimate ETo. Nine of them are classified as meteorological models, which used hybrid combinations of minimum and maximum air temperature, minimum and maximum relative humidity, and dew point temperature, while the remaining four are known to be thermodynamic basis models that require only the air temperature to function. The actual vapor pressure, the VPD, daily ETo, and cumulative ETo are computed by the thirteen models. Several statistical tests are used to evaluate the efficiency of each model. Model 5 is used as the standard to compare all other models. Results show that Model 13 performs better than any tested model in this study in terms of ETo estimation. In the meteorological group, Model 4 performs better than any model in this group with an R2 value of 0.9994.