Evaluation of Radiation-Based Reference Evapotranspiration Models Under Different Mediterranean Climates in Central Greece

Eighteen radiation-based equations used to estimate reference evapotranspiration (ET<Subscript>ref</Subscript>) were generalized into seven linear models. The general models were calibrated using the standard FAO-56 Penman-Monteith method. Model performance was evaluated under humid, sub-humid and semi-arid mediterranean climatic conditions in central Greece. Evaluation and comparison of the models was based on quantitative assessment of their ability to accurately estimate ET<Subscript>ref</Subscript> values, generated by the FAO-56 Penman-Monteith equation. All models provided relatively accurate estimates of ET<Subscript>ref</Subscript>. The Abtew model showed the best overall performance with respect to the data from all available climate stations of central Greece. The average error of the Abtew model in the monthly average daily ET<Subscript>ref</Subscript> estimates was 0.24 mm, which corresponds to a relative error of 7.7 %. The Abtew method has not yet been tested under mediterranean climatic conditions. Based on our results, it seems to be a good choice for the estimation of monthly average daily ET<Subscript>ref</Subscript> under different conditions in the mediterranean climate. An exception appears to be the mediterranean climate with relatively high humidity and low wind speed. Under these conditions the models of the Priestley-Taylor group, the Makkink group and the Jensen-Haise group performed better than the Abtew equation. Copyright Springer Science+Business Media Dordrecht 2014