Computing FAO56 reference grass evapotranspiration PM-ETo from temperature with focus on solar radiation

The computation of the reference crop evapotranspiration (ETo) using the FAO Penman-Monteith equation (PM-ETo) requires data on maximum and minimum air temperatures (Tmax, Tmin), vapour pressure deficit (VPD), solar radiation (Rs) and wind speed at 2 m height (u2). However, those data are often not available, or data sets may be incomplete or have questionable quality. Various procedures were proposed in FAO56 to overcome these limitations and...