Abstract: To explore the variation of relations between runoff and meteorological factors in Jingou River basin under varying circumstances, we examined the variations of hydrometeorological factors and the variations of relations between meteorological factors and runoff by using ESMD (Extreme-point Symmetric Mode Decomposition), Spearman's correlation analysis, and sliding Copula function based on the hydrometeorological data of Bajiahu hydrological station from 1964 to 2016. Results suggest that the runoff series of Jingou River basin displays a weak decreasing trend in general, while the precipitation and temperature series show an increasing trend. The ESMD trend item reflects that the runoff, precipitation and temperature series of Jingou River basin vary in a non-linear trend. The precipitation series and temperature series change abruptly in 1983 and 1997, respectively, while runoff series in 2002 and 2015. The correlation coefficients under different windows of the sliding Copula function indicate that the runoff-temperature relation varied abruptly in 1997. The optimum Copula function of the runoff-temperature joint series varied from the Gauss-Copula function in 1964-1997 to the Gumbel-Copula function in 1998-2016. Climate change and human activities are the dominant reasons for the variation of runoff-temperature relation in Jingou River basin.

Key words: runoff, meteorology, diagnosis of relational variation, sliding Copula function, ESMD, Spearman correlation analysis, Jingou River basin