Effects of climatic variation on pan-evaporation in the Poyang Lake Basin, China

Pan-evaporation is an important indicator of atmospheric evaporative demand and is used extensively in agriculture and hydrometeorology. This study investigated changes in pan-evaporation and the influence of large water bodies on pan-evaporation changes based on the latest data from 1959 to 2012 in the Poyang Lake Basin. The Mann-Kendall test showed that the annual pan-evaporation decreased dramatically (-8.21 mm yr(-2)) from 1959 to 1973, then decreased slowly (-5.00 mm yr(-2)) from 1974 to 1995, while it increased significantly (11.48 mm yr(-2)) from 1996 to 2012. A differentiation method was used to attribute the changes in climatic variables to the changes in pan-evaporation. A decrease in air temperature dominated the pan-evaporation decrease from 1959 to 1973, whereas decreases in wind speed and solar radiation dominated the pan-evaporation decrease from 1974 to 1995. However, significant increases in wind speed and air temperature dominated the pan-evaporation increase from 1996 to 2012. Furthermore, we studied the influence of Poyang Lake (the largest freshwater lake in China) on the changes in pan-evaporation. The amplitude of the changes in pan-evaporation near Poyang Lake was larger than that away from Poyang Lake. Pan-evaporation near Poyang Lake was more sensitive to changes in air temperature, wind speed, and vapor pressure than that in the regions away from the Poyang Lake, thereby resulting in larger changes in pan-evaporation in areas near the lake. Investigating changes in pan-evaporation is useful for agricultural irrigation planning and water management in the Poyang Lake Basin.