The evaluation of evapo-transpiration was taken over a paddy field in order to examine the utility of the Thornthwaite's method based on aerodynamic considerations which lead to the equation (1).
The values of the specific humidiy and total run of wind obtained with the aid of the relatively simple apparatus, namely, thermocouple psychrometer and Robinson type small anemometer, to keep the practicality are shown Table 1.
Houtly values of the rate of evapo-transpiration were evaluated from equation (1) by taking the zero-plane displacement d=47cm for the reasonable value from the observation and compared with the values of the direct measurement (see Fig. 1, Table 3).
The present experiment suggests that the practical application of the Thornthwaite's method will be possible to evaluate the evapo-transpiration from the natural surfaces by improving the method of observation.
