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

Abstract

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.