Potential evapotranspiration and its attribution over the past 50 years in the arid region of Northwest China

Evaporation paradox and its attribution have become a hot research topic in hydrology in recent years. This study estimates the potential evapotranspiration (ET0) using modified Penman-Monteith method and analyzes the corresponding trend attribution based on the long-term meteorological data collected at 81 ground-based meteorological stations in Northwestern arid region of China during the period 1958-2010. The analysis results show: (1) The ET0 has exhibited an obvious decreasing trend until the early 1990s; however, the downward trend has been reversed to an upward trend after then. (2) Decrease in diurnal temperature range (DTR) and wind speed (WS) may lead to the decrease of ET0 during 1956-1993. The change of dominant factors in the ET0 trend has differences after the early 1990s; observed increase in WS is the primary factor contributing to the reversion of ET0. Copyright (c) 2012 John Wiley & Sons, Ltd.