基于样本熵的渭河流域月降水序列复杂度与异步性特征研究

Study on Complexity and Asynchronism of Monthly Precipitation Series in the Weihe River Basin Based on Sample Entropy

降水序列复杂度是衡量气候系统复杂非线性变化的重要指标,其表征的时间序列动力学特征对应对全球气候变化及流域水资源适应性管理意义重大。基于渭河流域及其周边22个气象站的降水数据,采用非线性动力学参数样本熵、Mann-Kendall非参数趋势检验及累积距平等方法,系统分析1960-2016年渭河流域月降水序列复杂度的空间分布及演化特征,引入互样本熵探究气候变化影响下渭河流域不同分区月降水序列的异步性变化。结果表明:渭河流域月降水序列复杂度具有显著的空间差异性,表现为从东南向西北下降、从上游到下游上升的趋势,干流上游区复杂度分布与其他区域明显不同;近年来渭河流域降水量呈显著的下降趋势,降水序列样本熵值显著增大,说明降水动力学系统结构趋于复杂,可能会给渭河流域的水资源管理带来挑战;渭河流域不同分区的滑动平均降水量与相应的样本熵值间存在负相关关系,整体表现为降水量减小、复杂度提高;气候变化影响期内区域间月降水序列异步性有所增强,但变化并不显著。

The complexity of precipitation sequence is a critical indicator to measure the complex nonlinear characteristics of the climate sys⁃tem,effectively presenting the dynamic characteristics time series which are of great significance to the adaptive management of basin water resources responding to global climate change.In this study,the precipitation data of 22 meteorological stations in and around the Weihe Riv⁃er basin was selected,covering the period of 1960-2016,and the nonlinear dynamic parameter sample entropy,the Mann⁃Kendall trend test and the cumulative anomaly method were employed to analyze the spatial distribution and evolutionary characteristics of monthly precipitation sequence complexity in the basin.In addition,the cross⁃sample entropy method was introduced to explore the asynchrony of the precipitation sequence in various sub⁃regions of the Weihe River basin in climate⁃change⁃impacted period.The results show that the complexity of monthly precipitation sequence has obvious spatial differences in the whole basin,specially reflecting on the complexity in the east greater than that in the west,the south superior to the north.Also,it is seen that precipitation complexity is gradually increasing along the main river,and that the upstream area is distinctly different from other sub⁃regions;the precipitation in the basin has a significant downward trend in recent years,while the changes of its sample entropy value is large,showing an obvious increasing on the whole which implies that the systemic dy⁃namic structure of the precipitation is becoming more complex.It may bring great challenges to the regional watershed water resources man⁃agement;the statistical results in different sub⁃regions demonstrate negative correlations between the sliding average value of precipitation and the corresponding sample entropy value,i.e.precipitation decreasing along with complexity increasing,and a good correspondence is found between the peak⁃to⁃valley values of precipitation and the sample entropy;the spatial asynchrony has been increased in the whole basin dur⁃ing the impact period of climate change,but the change is not significant.