基于小波变换的径流周期与ENSO事件响应关系研究

在气候变化和人类扰动下,河川径流过程变化日益复杂,探索径流变化对气候因子(ENSO事件)的响应规律,掌握区域水资源发展动态,对科学制定区域水资源规划和管理策略及满足人类需求与生态系统的水平衡要求极为重要。通过交叉小波变换法与凝聚谱方法,分析陕西省渭河咸阳站、无定河丁家沟站、汉江安康站河川径流规律与ENSO事件的相关性,从物理驱动因素层面探讨径流周期变化的潜在机理。分析结果显示:20世纪70年代以前,各站径流与ENSO指数(MEI指数)在小尺度2~4 a周期上均存在着显著的负相关;从20世纪70年代开始,径流与ENSO指数的相关性变得复杂,这与研究区内人类活动影响增强并成为径流驱动的主因有关。研究表明:交叉小波变换法与凝聚谱方法适用于水文和气象要素间响应关系的分析,可深层次地揭示两者之间的相关性和响应时滞方面的联系,可反映气候因子对径流过程影响的时域变化特征。案例结果表明:陕西省河川径流变化在20世纪70年代以前主要受气候因子驱动,响应较为紧密;20世纪70年代以后,人类活动影响逐渐超越气候因子影响,径流变化表现为人类与气候双驱动模式,且以人类活动为主。

Analysis on the Responding Relationship between Runoff Period and ENSO Events Based on Cross-wavelet Transform

Under the condition of climate change and human disturbance, the river runoff process shows increasingly complex nonlinear change. Thoroughly understanding runoff changes in response to climate factors as ENSO events and grasping regional water resources change trend are of great importance to regional water resources planning and management and water balancing between river ecosystems and human demands in the present and future. This paper analyzed the correlation of runoff periodic change and ENSO events in Weihe River (Xianyang station), Wudinghe River (Dingjiagou station) and Hanjiang River (Ankang station) in Shaanxi Province by the methods of cross-wavelet transform and wavelet coherence spectrum, and studied the potential mechanism of runoff periodic variation from the aspect of physical driving factors. The results indicate that a significant negative correlation exists between runoff and ENSO e-vents (represented by MEI index) in the small scale as 2~4 years oscillation before 1970s, but after the 1970s, this correlation be-comes complicated and difficult to identify due to the impact of human activities which is the main driving factor of runoff. The research shows that the methods of cross-wavelet transform and wavelet coherence spectrum are applicable to the responding relationship analysis between hydrological process and climatic factors, which can deeply reveal the correlation between them and the response delay, and reflect the temporal variation of runoff process under the influence of climatic factors. Case study results demonstrate that river runoff change in Shaanxi Province is mainly driven by climatic factors before 1970s, but after 1970s, the impact of human activities is gradu-ally beyond climatic factors, so the runoff changes become under the dual drives of human and global climate and the main part is hu-man activities.