Abstract: In order to accurately estimate the reference crop evapotranspiration (ETc) of wheat using incomplete meteorological elements, three verification and analysis processes in estimation of some meteorological elements were carried out by using daily forecast weather data and the corresponding daily measured meteorological data of Xinxiang during winter wheat growing seasons from 2014 to 2016, as well as modified solar radiation parameters and adjustment coefficients. First, the accuracy of forecast air temperature was verified. Then, the actual water vapor pressure and solar radiation were estimated based on forecast air temperature. Finally, the forecast air temperature and averaged wind speed were adopted to estimate the reference ETc based on the Penman-Monteith formula. The results showed that the daily forecast air temperature could replace the daily observed air temperature, water vapor pressure and solar radiation using the forecast maximum and minimum temperature, which met the requirements of Penman-Monteith formula, and the accuracy of the radiation estimated using weather forecast data was higher than that of the aerodynamics. Generally, the accuracy of the radiation in the daily reference ETc estimated by weather forecast data was higher than that of the aerodynamics, the estimated values by weather forecast was relatively lower, and the underestimate rate was below 7%. Through statistical analysis, there was a high correlation between daily ETc estimated by weather forecast and that estimated by Penman-Monteith equation (R2=0.77). Therefore, it was feasible to use the daily meteorological data from weather forecast to estimate the reference ETc, and it was suggested to use the radiation method to estimate ETc in arid and semi-arid areas, which provided theoretical and methodological guarantee for agricultural irrigation forecast and had reference significance for guiding the optimal allocation of local agricultural water resources.

Key words: Daily meteorological data, Reference crop evapotranspiration, Temperature, Penman-Monteith formula