ESTIMATION OF EVAPORATION RATE BY USE OF A SONIC ANEMOMETER

Abstract

The evaporation rates from the water and soil surfaces are estimated by the eddy-correlation method which is, in principle, the most reasonable one, using a sonic anemometer and a fine thermocouple psychrometer. Cospectral analysis shows that the method seems to be applicable to the estimation of evaporation rate, in spite of rather long averaging time of 1 sec and short sampling duration of 5 min, taken here. The results are compared with those by the aerodynamic method, the heat-balance method and the pan method. It is found that there is a fairly good agreement between the results by the eddy-correlation method and those by Thornthwaite-Holzman's formula.