Comparation of Different Forms of Penman Equation

The research was carried out near Foggia (in Southern Italy) at 90 m above sea level and at 41° 27' N latitude, using two drainage lysimeters, filled with a silt clay soil and cultivated to reference grass (Festuca arundinacea), maintained at a 0.08 to 0.15 m height. This study was conducted to evaluate three different equations for reference crop evapotranspiration (ET), recommended by FAO: FAO-24 Penman, FAO-24 Corrected Penman and Penman-Monteith and estimate local calibration coefficients. Linear regression analysis was performed on the lysimeter weekly averaged values of ET as dependent variable and the ET estimates as independent variable. For simplicity and ease of use, aerodynamic and crop resistance parameters, required by the Penman-Monteith equation, were expressed as linear functions of mean plant height and for estimating the aerodynamic and radiative terms of this equation, where regression functions were used according to the most recent FAO guidelines.