Analysis of pan evaporation characteristics over land and water surfaces in the Three Gorges Reservoir area

The Three Gorges Reservoir (TGR) is the largest artificial water resources regulation and storage center in China. Thereby the evaporation in the reservoir area has profound impact on the regional eco-hydrological process. Analysis on the differences of pan evaporation characteristics between water surface and land surface is of great importance for understanding regional hydrological circulation and climate change. This work applied observations from both floating site and land site in Badong hydrometeorological station and the radiation data from ERA5 dataset, found the difference of seasonality characteristic of pan evaporation and energy budget between water surface and land surface, and preliminarily analyzed the reasons on the differences. The main results are as follows : ① Significant difference of seasonal pan evaporation characteristics was detected between water surface and land surface, with high peak appeared in August over land surface while appeared in December over water surface; ② The energy budget analysis indicating TGR area generally accumulated heat during summer season while released heat and significantly increased available energy in water during winter season, which resulted peak value appeared four months later in water site than that of the land site; ③ The controlling factors analysis indicated that the difference of evaporation and thermal characteristics was controlled by nonlinear comprehensive influences from multi micrometeorological factors, which was dominated by air temperature and saturated water pressure deficit during accumulating heat period (March to September), while by water temperature and temperature difference between air temperature and water temperature during releasing heat period (October to February of next year).