Spatial distribution and temporal variation of reference evapotranspiration during 1961–2006 in the Yellow River Basin, China

Abstract

To explore the spatial and temporal variations of the reference evapotranspiration (ET ref ) is helpful to understand the response of hydrological processes to climate changes. In this study, ET ref was calculated by the Penman-Monteith method (P-M method) using air temperature, wind speed, relative humidity and sunshine hours at 89 meteorological stations during 1961-2006 in the Yellow River Basin (YRB), China. The spatial distribution and temporal variations of ET ref were explored by means of the kriging method, the Mann-Kendall (M-K) method and the linear regression model, and the causes for the variations discussed. The contribution of main meteorological variables to the variations of ET ref was explored. From the results we found that: (1) the spatial distributions of ET ref display seasonal variation, with similar spatial patterns in spring, summer and autumn; (2) temporal trends for ET ref showed large variation in the upper, middle and lower regions of the basin, most of the significant trends (P = 0.05) were detected in the middle and lower regions, and, in particular, the upward and downward trends were mainly detected in the middle region and lower region of the basin, respectively; and (3) sensitivity analysis identified the most sensitive variable for ET ref as relative humidity, followed by air temperature, sunshine hours and wind speed at the basin scale. © 2011 IAHS Press.