西北干旱区阿克苏河径流对气候波动的多尺度响应

基于阿克苏河流域1960~2010年的气象、水文观测数据,利用集合经验模态分解（EEMD）方法,对研究期内阿克苏河径流时间序列进行多尺度的分析,并探讨其在不同时间尺度上的振荡模态结构特征及其对气候因子的多尺度响应。结果表明：① 近50年来,阿克苏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3 a和准6~7 a的周期性波动,在年代际尺度上表现出准13 a和准25 a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。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研究时期内的波动趋势,重构的径流年代际变化则有效揭示了阿克苏河径流在不同年代丰、枯水期交替出现的状态。③ 在年际尺度上径流与气温、降水和潜在蒸发都表现为不显著的正相关关系,而在年代际尺度上,径流量与气温和降水均表现为显著的正相关关系,与潜在蒸发表现为显著的负相关关系,且在年代际尺度上相关性和显著性明显强于年际尺度,表明年代际尺度更适于评价径流对气候波动的响应。结果表明EEMD是一种甄别非线性趋势和尺度循环的有效方法。

Multi-scale Response of Runoff to Climate Change in the Aksu River Basin in Arid Area of the Northwestern China

On the basis of the hydrological and meteorological data in the Aksu River Basin during 1960-2010, the multi-scale characteristics of runoff variability were analyzed using the ensemble empirical mode decomposition method (EEMD), and the aim is to investigate the oscillation mode structure characteristics of runoff change and its response to climate fluctuation at different time scales. Results indicated that in the past 50 years, the overall runoff of Aksu River in northwestern China has exhibited a significant non-linear upward trend, and its changes obviously manifested quasi-3 and quasi-6-7 years at inter-annual scale and showed quasi-13 and quasi-25 years at inter-decadal scale. Variance contribution rates of each component showed that the inter-annual change held a dominant position in the overall runoff change, and the inter-decadal change also played an important role in the overall runoff change for the Aksu River. The reconstructed inter-annual variation could describe the fluctuation state of original runoff during the study period; the reconstructed inter-decadal variability effectively revealed that the runoff for the Aksu River changed over the years, namely the state of abundance and low water period appear alternately. In addition, we found that runoff has a positive correlation to precipitation, temperature and potential evaporation (PET) at the inter-annual scale, but not significant in statistics. The runoff has a significant positive correlation to precipitation and temperature whereas a negative correlation to PET at the inter-decadal scale, furthermore, they are more significant and relevant at inter-decadal scale, indicating that the inter-decadal scale is more suitable for investigating the responses of runoff dynamics to climate fluctuation. Meanwhile, the results also suggested that EEMD is an effective method to distinguish the non-linear trend from multi-scale variability of non-linear and non-stationary signal and can be helpful to deepen the understanding of the multi-scale characteristics for runoff in arid area of the northwestern China.