开都河源流区径流的非线性变化特征及其对气候波动的响应

Runoff nonlinear variation and responses to climate fluctuation in the headwater region of the Kaidu River

非线性是现代水文学研究的重要前沿问题之一,对揭示水文系统变化规律及其复杂性具有重要意义。基于开都河源流区气象和水文站1960-2012年实测数据,采用集合经验模态分解方法,对研究期内开都河年径流时间序列进行多尺度分析,并探讨其在不同时间尺度上的非线性变化特征及其对气候因子的多尺度响应。研究结果表明:(1)近50年来,开都河年径流整体上呈现出显著的非线性增加趋势,且其变化在年际尺度上表现出准2~3a和准4~5a的周期性波动,在年代际尺度上表现出准10~11a和准26~27a的周期性变化;(2)各周期分量的方差贡献率表明,年际振荡在径流长期变化中占据主导地位,年代际尺度在径流变化过程中也起着重要作用;(3)重构的径流年际变化能够较为详细地描述原始径流序列在整个研究时段的波动状况,二者在变化趋势上基本是一致的;重构的径流年代际变化则有效揭示了开都河径流量在1995年出现了由负距平到正距平的转折;(4)在重构的年际尺度和年代际尺度上,降水与径流的相关性都强于气温、潜在蒸发与径流的相关性,说明降水是影响开都河径流变化的决定性因素;而在年代际尺度上降水、气温和潜在蒸发的相关性都要明显强于年际尺度,表明年代际尺度是评价该区径流对气候波动响应过程的较佳尺度。

Nonlinearity is one of important frontier issues in the field of modem hydrology. It is of great significance to discover the variation and the complexity of the hydrological system. On the basis of hydrological and meteorological data in the headwater region of the Kaidu River from 1960 to 2012, multi-scale characteristics of runoff variability were analyzed using the ensemble empirical mode decomposition method to investigate nonlinear change characteristics of runoff at different time scales and multi-scale responses to climate fluctuation. We found that in the past 50 years, the overall runoff of Kaidu River in Xinjiang has exhibited a significant non-linear increasing trend, and changes have manifested at quasi-2-3 and quasi-4-5 year inter-annual scales and showed quasi-10-11 and quasi-26-27 year inter-decadal scales. Variance contribution rates of each periodic component showed that inter-annual change held a dominant position in the long- term change of runoff, and inter-decadal change also played an important role in the overall runoff change for Kaidu River. Reconstructed inter-annual variation describes the fluctuation state of original runoff during the study period, that is to say the trends of both are basically the same. The reconstructed inter-decadal variability shows that the runoff of Kaidu River underwent a significant transition in 1995 from low to high, namely the state of runoff anomaly shifting from a negative phase to a positive abundance water period. In addition, we found that the correlation between runoff and precipitation is more relevant and significant at both the inter-annual and inter-decadal scales compared to the correlation between runoff and temperature and potential evaporation, indicating that precipitation is the decisive factor for changes in runoff. Corrections between runoff and precipitation, temperature and potential evaporation are more significant and relevant at the inter-decadal scale than inter-annual scale, suggesting that the inter-decadal scale is more suitable for investigating responses of runoff dynamics to climate fluctuation.