变化环境下流域气象水文要素的相关性演化

Evolution of correlation analysis of hydro-meteorological variables in the basin under changing environment

为了探究流域气象水文要素间相关性结构及其演化,采用交叉小波分析、去趋势波动分析(DFA)、去趋势互相关分析(DCCA)和去趋势偏互相关分析(DPXA)对渭河流域1960-2015年的气象水文数据(年降水量、年蒸发皿蒸发量、年径流深等)进行了时频域相关性分析和长程相关性分析,探讨气象水文要素间的相关性结构变化和长程相关性特征。交叉小波分析表明,研究期内蒸发、降水、径流任意两因子间相关性在不同时频域存在差异,相关结构上存在1~2和8a的相似主导周期,宏观上降水-径流间多尺度相关结构发生退化,共振周期减少。长程相关分析表明,径流、蒸发和降水序列的Hurst指数均大于0.5,表现出良好的长持续性特征,当前降水(径流、蒸发)会对未来某一时刻的降水(径流、蒸发)产生影响;DCCA结果表明,降水-径流间表现出长程相关性,而降水-蒸发和径流-蒸发呈长程反相关性,呈现出不同的长程互相关结构;DPXA结果表明,扣除第三因子影响后,降水-蒸发和径流-蒸发长程相关性发生突变,从而降水-径流、降水-蒸发和径流-蒸发两两间均呈长程互相关性,暗示降水、径流和蒸发三者间长程相关性的互馈特征,相比于DCCA结果,DPXA的结果显然更具有说服力。透过滑窗分析可发现降水-径流、降水-蒸发之间的长程互相关性在时域上没有发生突变,未来降水量的可能增加将引起径流量增大,并间接引起渭河流域受水量制约的蒸发量增大;径流-蒸发间长程互相关性于1962年由长程反相关突变为长程相关,随后长程相关性持续增强,标志着渭河流域未来蒸发的变化可能会引发更大的径流波动。

In order to evaluate and investigate the correlation structures of hydro-meteorological variables in the Wei River basin,the time-frequency domain correlation analysis and long-range correlation analysis were carried out by cross wavelet analysis,detrended fluctuation analysis(DFA),detrended cross-correlation analysis(DCCA),and detrended partial cross-correlation analysis(DPXA).The results of cross wavelet analysis show that correlation between precipitation(P),pan evaporation(E),and runoff depth(R)differ at different time-frequency domain.In terms of correlation structure,there were 1-2 years and 8-year periods existed in the system consisted of P,R,and E.On the macro scale,the multi-scale correlation structures between precipitation and runoff degraded and resonance period were reduced.Long-range correlation analysis showed that the Hurst index of R,E,and P sequences were greater than 0.5,showing long-term persistence characteristics.The current precipitation(runoff and evaporation)might have an impact on the precipitation(runoff and evaporation)at a certain time in the future.The DCCA results show that there was a long-range correlation between P and R,while an inverse long-range correlation existed between P-E and R-E,showing different cross-correlation structures.The DPXA results show that the long-range correlation change and turn into long-range correlation,implying the feed-back characteristics of long-range correlation among P,R,and E.Compared with the results of DCCA,the DPXA was more persuasive.The sliding-window analysis(30 years)showed that the long-range correlation between P-R and P-E did not change in the time domain,and the possible increase of precipitation in the future may lead to the increase of runoff and indirectly lead to the increase of evaporation in the Wei River basin.The long-range correlation between R-E changed from long-range inverse correlation to long-range correlation in 1962,and then the long-range correlation continued to increase,indicating that future evaporation changes in the Wei River basin may cause more runoff fluctuations.Therefore,water resources management based on ET control may have a certain significance to increase the available water amount in the Wei River basin.