Coupling effect between thermal and dynamic factors on water surface evaporation and in-situ observation

Water surface evaporation is an important indicator of atmospheric circulation and hydrological cycle. This paper, after selecting representative alluvial plain in north of Haihe River Basin as the experimental point, designs in-situ observation experiment to explore the influence of wind speed on water surface evaporation and puts forward the coupling effect between thermal and air dynamic factors on evaporation, which refers to that actual evaporation is not only depended on the values of thermal factor and dynamic factor, but also on the correlation of the two factors. The observed data show that, the main factors influencing actual evaporation in experimental area are daily average air temperature and wind speed and the two variables are separately the main representation of thermal factor and air dynamic factor. It is proved that there is significant coupling effect between daily average temperature and wind speed on observed evaporation. At last, Penman Formula is analyzed to explore the theoretical evidence of the coupling effect, it is concluded that the structure of Penman Formula should be revised later to further characterize the coupling effect between thermal and air dynamic factors on evaporation. As a whole, coupling effect is a basic principle in evaporation, which could be the reference to explain “Evaporation Paradox”.