长江上游径流混沌动力特性及其集成预测研究

针对长江上游干流主要站点月径流时间序列强非线性和非平稳特征,引入混沌理论和AdaBoost.RT集成极限学习机方法对其月径流时间序列进行分析和预测。首先,以流域径流非线性动力系统混沌特征参数辨识为切入点,研究并发现了流域内在特性作用下月径流时间序列动力响应的混沌现象,推求了月径流时间序列相空间重构的延迟时间和最佳嵌入维数,在此基础上,以重构相空间时间序列作为输入变量,引入基于自适应动态阈值的改进AdaBoost.RT算法改进极限学习机模型的学习性能,得到最佳的混沌集成学习月径流时间序列预测模型。实例研究结果表明,所提方法和模型能够显著提高单一极限学习机模型的泛化性和稳定性,从而获得更优越的预报性能。

Chaotic Dynamic Characteristics and Integrated Prediction of Runoff in the Upper Reaches of Yangtze River

In view of the strong nonlinearity and non-stationarity of monthly runoff in the upper reaches of Yangtze River, a hybrid model integrating the chaos theory and an ensemble AdaBoost.RT extreme learning machine is proposed for monthly runoff analysis and prediction. Firstly, the chaotic characteristics of monthly runoff in watershed were researched and revealed based on parameter identification of the runoff system. The optimal delay time and embedding dimension of the monthly runoff time series are deduced. Secondly, with the time series of the reconstructed phase space matrix as input variables, an improved AdaBoost. RT algorithm based on self-adaptive dynamic threshold was incorporated to improve the performance of extreme learning machine. Finally, the optimal chaotic ensemble learning model for monthly runoff prediction was obtained. Results showed that the proposed model could evidently improve the generalization and stability of single extreme learning machine model, and thus achieve better prediction performance.