Analysis Of Multiple Time Scales Feature And Chaotic Characteristics And Prediction Of Tree Ring

Global warming has attracted worldwide attention.The growth of trees belongs to the natural climate system,which is extremely complex.Further research of the climate system is helpful to further understand the mechanism of nature.Climate characteristics of an area are reflected in the growth of tree ring.Therefore,in order to explore the climate behavior in this area,the tree ring width in Huangdi Tomb from 1470 to 1974 is taken as the research object,and the multiple time scales and chaotic characteristics are analyzed based on mode decomposition method and chaotic dynamics theory.In addition,the correlation between tree ring and sunspot activity is discussed,and the tree ring width is predicted based on phase space reconstruction.The main works include:(1)The multiple time scales and chaotic characteristics are analyzed based on ensemble empirical mode decomposition and chaotic dynamics theory.The results show that the tree ring width is mainly composed of periodic components,chaotic components and a trend component,and they have multiple time scales and chaotic characteristics.In the multiple time scale analysis,the results are still the same as the tree ring width removed chaotic components and a trend component,but chaotic characteristics become stronger if the periodic components and a trend component are removed.The conclusions are helpful for further understanding of the climate system.(2)According to the correlation of tree ring and solar activity,cycle analysis method based on the variational mode decomposition(VMD)and Hilbert transform is proposed.The results show that the tree ring width has the quasi-periodic of 2 to 7a,10.8a and 25a;the sunspot number has the quasi-periodic of 8.3a,9.9a,11.1a,52.2a and 101.2a.The result by analyzing of those quasi-periodicity shows that the main periods of tree ring width and the sunspot number in the same period are basically consistent,and tree ring width has other cycles.This shows that sunspot activity is an important factor affecting tree ring growth,and tree ring width is influenced by other external environments.(3)A variational mode decomposition-VOLTERRA coupling prediction model based on chaotic theory is proposed.On the basis of chaotic identification of tree ring width sequence,the tree ring width is decomposed by VMD,and then the phase space of each IMF are reconstructed and predicted by the third order VOLTERRA adaptive model.Finally,the predicted value of the original sequence is obtained by summation.The results show that the model has better prediction accuracy than other models and can improve prediction accuracy effectively.