A wind tunnel experiment on the evaporation rate of Class A evaporation pan

SummaryThe influences of wind speed and water depth on the evaporation rates of Class A evaporimeter pan were investigated in a series of wind tunnel experiments. Based on the measured pan evaporation rates, the aerodynamic resistance for the evaporimeter pan was calculated and integrated with a Penman–Monteith type model for pan evaporation rate. The experimental results also demonstrated that the evaporation rate of evaporimeter pan will be influenced by the water depth when the water depth is much smaller than the standard water depth h = 20 cm, due to the shelter effect of the rim of the pan. In addition, it was observed that the wind could blow water over the edges of the pan when wind speed U exceeds 7.0 m s−1. Namely, the water loss from the pan is not entirely due to evaporation and the evaporation rates could be over-estimated at high wind speeds.