The temporal trends of reference evapotranspiration and its sensitivity to key meteorological variables in the Yellow River Basin, China

✍ Scribed by Qiang Liu; Zhifeng Yang; Baoshan Cui; Tao Sun

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 460 KB
• Volume: 24
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/hyp.7649

✦ Synopsis

The temporal trends of reference evapotranspiration (ET ref ) reflect the combined effects of radiometric and aerodynamic variables, such as global solar radiation (R s ), wind speed, relative humidity and air temperature. The temporal trends of annual ET ref during 1961-2006 calculated by Penman-Monteith method were explored and the underlying causes for these trends were analysed in the Yellow River Basin (YRB). The contributions of key meteorological variables to the temporal trend of ET ref were detected using the detrended method and then sensitivity coefficients of ET ref to meteorological variables were determined. For ET ref , positive trends in the upper, middle and whole of YRB, and significant negative trend (P D 0Ð05) in the lower basin were obtained by the linear fitted model. Significant increasing trend (P D 0Ð05) in air temperature and decreasing trend in relative humidity were the main causes for the increasing trends of ET ref in the upper, middle and whole basins. For the whole basin, the increasing trend of ET ref was mainly caused by the significant increase (P D 0Ð05) in air temperature and to a lesser extent by a decrease in the relative humidity, decreasing trends of R s and wind speed reduced ET ref . The spatial distribution of sensitivity coefficients addressed that the sensitive regions for ET ref response to the changes of the four meteorological variables are different in the YRB. The sensitive region lay in the upper basin for R s , the northwest portion of the middle basin for wind speed, the south portion of YRB for relative humidity and the west portion of the upper basin and the north portion of the middle basin for air temperature. In general, R s was the most sensitive variable for ET ref , followed by relative humidity, air temperature and wind speed in the basin scale.