The evaluation of 27 potential evapotranspiration (PET) formulas for rainfall-runoff modelling applications (Oudin, 2004; Oudin et al., 2005) led to a simple and efficient PET formula that allows obtaining better results than the other formulas tested, in terms of simulation of streamflows.
This formula is detailed in Oudin et al. (2005). It uses temperature as the only input data. It also uses the computation of extraterrestrial radiation detailed by Morton (1983).
Pay attention to units when applying the formula (for more information on conversions, see here).
To know more: check our publications.