| The Indian monsoon system is a prevailing wind system in the Indian Ocean region,which controls equatorial and tropical climate of South Asia and Africa by through and vapor, thus affecting the production and living in these regions. Therefore, a multi-scale exploration of the change rule and formation mechanism of the Indian monsoon over the last millennium is necessary,which isconducive to understanding rules of monsoon evolution from a new perspective and predicting the future trend of climate change.Empirical Mode Decomposition (EMD) method is applicable to analyzing the non-linear and non-stationary time series, for it can quickly decompose fluctuations at different frequencies from the signal according to the frequency from high to low, and the last remainder is the trend component of data sequence. In this thesis, the Empirical Mode Decomposition method is used to make multi-scale analysis on the time series of the stalagmite518O record of Jhumar cave(AD.1075-2008) in central India, the stalagmite δ18O record of Heshang cave(AD.1071-2002), and three driving factors-E1Nino/Southern Oscillation (ENSO) index,10Be sequence, the North Pacific Decadal Oscillation Index (PDO).Whose purpose is to explore the evolution characteristics and formation mechanism of the Indian monsoon in the last millennium, and to conduct a comparative analysis of the change in different scales and formation mechanism of Indian monsoon and East Asian monsoon, and to analyze the phase relationship between the Indian monsoon and east Asian monsoon nearly one thousand years.It is showed that2.4,5.4,13,28,61,132,292,682,932years of quasi-periods found in the level changes of Indian summer monsoons nearly a thousand years by decomposing stalagmite δ18O record of Jhumar cave through EMD, of which13,61,132,292years is the main cycles of Indian summer monsoon. Variance contribution rate of trend term is the biggest and the value of the stalagmite δ18O decreased gradually, this process is relatively slow and stable, indicating that the Indian monsoon has been strengthening nearly a thousand years.In addition, it is showed27,55,133,311,933years of cycles, such as obvious periodic components, found in the stalagmite δ18O record of Jhumar cave nearly a thousand years through power spectrum analysis. These cycles are basically identical to the 28,61,132,292,932years periods by EMD. But2.4,5.4and13years found by EMD, such as small scale cycles, aren’t clearly shown in power spectrum analysis.Therefore EMD has the advantage of clearly decomposing small scale fluctuation cycles.The EMD method is applied to analyse three driving factors in Multi-scales. ENSO reveals that3,5.9,11,20,46.7,87,210,351and846years of quasi-periodic changes;18Be data sequence on behalf solar activity shows that3.4,8,62,123,218,955,977years of quasi-periods; PDO index series has3.4,7.5,15,38,67,184,457,607years of quasi-periodic fluctuations in the last millennium.We can discover that quasi2.4,5.4years existed in the Indian summer monsoon nearly a thousand years are consistent with quasi3,5.9years revealed in ENSO index, so significant short-period fluctuations in the Indian summer monsoon are associated with ENSO. In addition, the Indian summer monsoon exists quasi13year cycle, which may also be associated with quasi11-year cycle of ENSO. Fluctuations in61,132,932years of quasi-period of Indian summer monsoon are coincided basically with62,123,955years quasi-period revealed in10Be, it indicates that changes of Indian summer monsoon are affected by solar activity in centennial and millennial timescales. Indian monsoon fluctuations of2.4,5.4,13,61,682years’quasi-periods are basically close to3.4,7.5,13,61,607years’ quasi-periods of PDO, indicating that changes of Indian summer monsoon are affected by PDO in interannual, multidecades and millennial timescales. Combined with the variance contribution rate, the the Indian summer monsoon at interannual scale is affected mainly by ENSO, the second is associated with the PDO; interannual scale is related to all three driving factors and, mainly related to the PDO, followed by the ENSO and solar activity; centennial scale related to solar activity; millennial Scale may be related to PDO; trend term of solar activity has the most significant impact on the overall trend of the Indian summer monsoon.Through the multi-scale analysis and comparative studies on formation mechanism of the Indian monsoon and East Asian monsoon nearly a thousand years, we found that interannual scale fluctuations2.4,5.4years’quasi-pefiods of the Indian monsoon and4.7years in the East Asian monsoon, are mainly affected by the impact of the El Nino/Southern Oscillation (ENSO), followed by the interannual North Pacific Oscillation (ENSO).13-year cycle of the Indian monsoon and10-year cycle fluctuations series of East Asian monsoon, to some extent, are governed by the El Nino/Southern Oscillation, but the former is mainly affected by the interannual North Pacific Oscillation (ENSO). On the multi-decade scale, the Indian monsoon is related to the PDO and solar activity; The east Asian monsoon is not obvious relationship with three driving factors.132-year quasi-period in the Indian monsoon changes and112-year quasi-period in the East Asian monsoon are driven by solar activity. In addition, the Indian monsoon in millennium scale is associated with solar activity.The phase relationship between the Indian monsoon and East Asian monsoon nearly a thousand years is discussed. From the overall characteristics of the two original curves, the two monsoon have a basic synchronization. Through contrasting the same time scale of them, they also have a basic synchronization on century scale and millennial scale, but have lagged or advanced phenomenon. But on different scales, different time periods, phase relationship of them is different, showing alternating positive and negative phase. This paper also finds that the Indian monsoon and east Asian monsoon have quasi-doubling frequency in the interannual, multi-decade and century scales; they are controled by different power system on large scales. |
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