Advances in Geosciences www.adv-geosci.net 1680-7340 1680-7359 18 Advances and visions in large-scale hydrological modelling 2008 10.5194/adgeo-18-15-2008 http://www.adv-geosci.net/18/15/2008/ http://www.adv-geosci.net/18/15/2008/adgeo-18-15-2008.html http://www.adv-geosci.net/18/15/2008/adgeo-18-15-2008.pdf 15 23 2008-06-20 A global comparison of four potential evapotranspiration equations and their relevance to stream flow modelling in semi-arid environments M. Weiß weiss@cesr.de L. Menzel Center for Environmental Systems Research, University of Kassel, Kurt-Wolters-Str. 3, 34109 Kassel, Germany This study compares four different potential evapotranspiration equations according to Priestley Taylor, Kimberly Penman, Penman Monteith (FAO-56) and Hargreaves on a global basis to demonstrate their difference, and assess their impact on the calculation of stream flows. The various equations of potential evapotranspiration show great differences in magnitude. 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