In this work, different methods of determination of pan coefficient (Kp) for a daily estimation of referential evapotranspiration (ETo) using the "Class A" pan method (TCA) were analyzed. Methodologies proposed by Allen et al. (1998), Bernardo et al. (1996), Cuenca (1989) and Snyder (1992) were evaluated, and values of daily ETo estimated using TCA were compared to ones estimated by Penman-Monteith (FAO-56). A ten years historical series of data collected from an automatic station, Thies Clima model, was used installed at evapotranspiration station of Universidade Estadual do Norte Fluminense (UENF). A good fulfillment of Class A pan to estimate daily values of ETo by different ways to calculate Kp (R² > 0.79 and D > 0.90) was verified, with Cuenca (1989), Bernardo et al. (1996), and Allen (1998) methods showing the same concordance index (D = 0.95). The smallest absolute mean error (0.50) was showed by Cuenca (1989) method, which also presented the highest efficiency (EF = 0,81).
irrigation management; Penman-Monteith; agrometeorology
