Attribution analyses of potential evapotranspiration changes in China since the 1960s

This paper focuses on the primary causes of changes in potential evapotranspiration (ET_o) in order to comprehensively understand climate change and its impact on hydrological cycle. Based on modified Penman-Monteith model, ET_o is simulated, and its changes are attributed by analyzing the sensitivity of ET_o to influence meteorological variables together with their changes for 595 meteorological stations across China during the period 1961–2008. Results show the decreasing trends of ET_o in the whole country and in most climate regions except the cold temperate humid region in Northeast China. For China as a whole, the decreasing trend of ET_o is primarily attributed to wind speed due to its significant decreasing trend and high sensitivity. Relative humidity is the highest sensitive variable; however, it has negligible effect on ET_o for its insignificant trend. The positive contribution of temperature rising to ET_o is offset by the effect of wind speed and sunshine duration. In addition, primary causes to ET_o changes are varied for differing climate regions. ET_o changes are attributed to decreased wind speed in most climate regions mainly distributed in West China and North China, to declined sunshine duration in subtropical and tropical humid regions in South China, and to increased maximum temperature in the cold temperate humid region.