Abstract
The Makkink equation can estimate potential evaporation using only air temperature and sunshine duration. Therefore, it is convenient for use in developing countries where there is an insufficient amount of meteorological data. The two coefficients employed in the equation were determined to fit the estimations of the Penman equation, and the accuracy of the estimations by the Makkink equation were investigated. The results showed that the accuracy was best when the estimations were made with the coefficients which depend on each locality, and that the accuracy was further improved with the coefficients which depend on each climatological zone. The relationship between the two coefficients showed a negative correlation, which was addressed in a previous study.
