沂河径流非线性变化特征对气候变化的响应

目的]研究沂河水文和气候因子在不同时间尺度上的非线性变化特征,为进一步了解径流对气候变化的复杂响应过程提供理论依据。方法]采用集合经验模态分解(EEMD)、Mann-Kendall检验、相关分析和线性回归等分析方法。结果]1951—2013年沂河径流呈显著下降态势(p0.01),下降速率为3.33×108 m3/10a,但在1976年前后径流则呈相反变化趋势。同时,径流可分解为4个经验模态分量(IMF),其中在年际尺度上(周期为3和6a)的变化对径流总体变化的贡献率较大,为58%,其次是在数年代际(周期为31a)尺度上的变化,贡献率为11%,而在年代际(周期为13a)尺度上的变化对径流总体变化的贡献较小,仅为6%。故径流变化的非线性变化趋势对径流变化的贡献率为25%。结论]气候因子在不同时间尺度上对径流的作用方式和影响机理具有明显差异,其中在年代际和数年代际尺度上气候因素与径流关系更为密切。

Nonlinear Variation of Runoff and Its Response to Climate Change in Yihe River

Objective] Studying the nonlinear variations of runoff in Yihe River and the climate factors in different time scales, which was expected to provide theoretical basis for analizing the impact of climate change on runoff. Methods] The methods of ensemble empirical mode decomposition(EEMD), Mann-Kendall test, Pearson correlation analysis and Linear regression were adopted. Results] The runoff appeared a significant linear downward trend(p<0.01) during 1951-2013, with a rate of 3.33×10⁸ m³/10 a butan aberrant trend existed around 1976. Meanwhile, runoff was decomposed into four IMFs. The contribution of variance of inter-annual scale(quasi-3 and quasi-6-year) to the overall one was the largest, reaching 58%. The contributions of inter-decadal scale(quasi-13-year) and multi-decadal scale(quasi-31-year) were 11% and 6%, respectively. Subsequently, the contribution of nonlinear variation to the overall runoff was 25%. Conclusion] The effects of climate factors(PDO, ENSO, temperature and precipitation) in different time-scales on runoff and its mechanism were proved different. The climate factors in inter-decadal scale and multi-decadal scale are more closely related to runoff change.