Spatiotemporal trends of reference evapotranspiration and its driving factors in the Beijing-Tianjin Sand Source Control Project Region, China

In the water-limited Beijing-Tianjin Sand Source Control Project Region, reference evapotranspiration (ETO) is a vital hydrological factor for the revegetation implementation, and its long-term variation is of much interest in climate change studies. In our study, temporal and spatial patterns in ET and related driving factors in the project region are evaluated for the period 1959-2011, based on daily data from 46 meteorological stations, using Mann-Kendall CM-K) test, Sen's slope estimator, and multivariate regression. The results indicated that annual ETO had an insignificant decreasing trend in the study area, in which 15 stations showed significant negative trends and only 1 station showed significant positive trend at the 95% confidence level. Significant downward ETO was detected in the north sub-region (I) in spring, in the west sub-region (II) in summer and autumn. Analysis of the impacts of meteorological variables on spatiotemporal trends of ETO showed that wind speed was the most dominant factor affecting ETO variation at 35 stations. Downward ETO induced by decreased wind speed may be result from revegetation of Beijing-Tianjin Sand Source Control Project. In addition, ET change was influenced by sunshine duration in summer and maximum air temperature in winter. Better understanding ET response to climate change will enable efficient use of water resources and vegetation management, which could improve the ecological and environmental quality in Beijing, Tianjin, and the surrounding areas. (C) 2014 Elsevier B.V. All rights reserved.