TY - JOUR A1 - Malik, Nishant A1 - Zou, Y. A1 - Marwan, Norbert A1 - Kurths, Jürgen T1 - Dynamical regimes and transitions in plio-pleistocene Asian monsoon JF - epl : a letters journal exploring the frontiers of physics N2 - We propose a novel approach based on the fluctuation of similarity to identify regimes of distinct dynamical complexity in short time series. A statistical test is developed to estimate the significance of the identified transitions. Our method is verified by uncovering bifurcation structures in several paradigmatic models, providing more complex transitions compared with traditional Lyapunov exponents. In a real-world situation, we apply this method to identify millennial-scale dynamical transitions in Plio-Pleistocene proxy records of the South Asian summer monsoon system. We infer that many of these transitions are induced by the external forcing of the solar insolation and are also affected by internal forcing on Monsoonal dynamics, i.e., the glaciation cycles of the Northern Hemisphere and the onset of the Walker circulation. Y1 - 2012 U6 - https://doi.org/10.1209/0295-5075/97/40009 SN - 0295-5075 VL - 97 IS - 4 PB - EDP Sciences CY - Mulhouse ER - TY - JOUR A1 - Goswami, Bedartha A1 - Boers, Niklas A1 - Rheinwalt, Aljoscha A1 - Marwan, Norbert A1 - Heitzig, Jobst A1 - Breitenbach, Sebastian Franz Martin A1 - Kurths, Jürgen T1 - Abrupt transitions in time series with uncertainties JF - Nature Communications N2 - Identifying abrupt transitions is a key question in various disciplines. Existing transition detection methods, however, do not rigorously account for time series uncertainties, often neglecting them altogether or assuming them to be independent and qualitatively similar. Here, we introduce a novel approach suited to handle uncertainties by representing the time series as a time-ordered sequence of probability density functions. We show how to detect abrupt transitions in such a sequence using the community structure of networks representing probabilities of recurrence. Using our approach, we detect transitions in global stock indices related to well-known periods of politico-economic volatility. We further uncover transitions in the El Niño-Southern Oscillation which coincide with periods of phase locking with the Pacific Decadal Oscillation. Finally, we provide for the first time an ‘uncertainty-aware’ framework which validates the hypothesis that ice-rafting events in the North Atlantic during the Holocene were synchronous with a weakened Asian summer monsoon. Y1 - 2018 U6 - https://doi.org/10.1038/s41467-017-02456-6 SN - 2041-1723 VL - 9 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Maheswaran, Rathinasamy A1 - Agarwal, Ankit A1 - Sivakumar, Bellie A1 - Marwan, Norbert A1 - Kurths, Jürgen T1 - Wavelet analysis of precipitation extremes over India and teleconnections to climate indices JF - Stochastic Environmental Research and Risk Assessment N2 - Precipitation patterns and extremes are significantly influenced by various climatic factors and large-scale atmospheric circulation patterns. This study uses wavelet coherence analysis to detect significant interannual and interdecadal oscillations in monthly precipitation extremes across India and their teleconnections to three prominent climate indices, namely, Nino 3.4, Pacific Decadal Oscillation, and Indian Ocean Dipole (IOD). Further, partial wavelet coherence analysis is used to estimate the standalone relationship between the climate indices and precipitation after removing the effect of interdependency. The wavelet analysis of monthly precipitation extremes at 30 different locations across India reveals that (a) interannual (2-8 years) and interdecadal (8-32 years) oscillations are statistically significant, and (b) the oscillations vary in both time and space. The results from the partial wavelet coherence analysis reveal that Nino 3.4 and IOD are the significant drivers of Indian precipitation at interannual and interdecadal scales. Intriguingly, the study also confirms that the strength of influence of large-scale atmospheric circulation patterns on Indian precipitation extremes varies with spatial physiography of the region. KW - Extreme precipitation KW - Teleconnection patterns KW - Wavelets KW - Partial wavelet coherence KW - India Y1 - 2019 U6 - https://doi.org/10.1007/s00477-019-01738-3 SN - 1436-3240 SN - 1436-3259 VL - 33 IS - 11-12 SP - 2053 EP - 2069 PB - Springer CY - New York ER - TY - JOUR A1 - Ozturk, Ugur A1 - Marwan, Norbert A1 - Korup, Oliver A1 - Saito, H. A1 - Agarwa, Ankit A1 - Grossman, M. J. A1 - Zaiki, M. A1 - Kurths, Jürgen T1 - Complex networks for tracking extreme rainfall during typhoons JF - Chaos : an interdisciplinary journal of nonlinear science N2 - Reconciling the paths of extreme rainfall with those of typhoons remains difficult despite advanced forecasting techniques. We use complex networks defined by a nonlinear synchronization measure termed event synchronization to track extreme rainfall over the Japanese islands. Directed networks objectively record patterns of heavy rain brought by frontal storms and typhoons but mask out contributions of local convective storms. We propose a radial rank method to show that paths of extreme rainfall in the typhoon season (August-November, ASON) follow the overall southwest-northeast motion of typhoons and mean rainfall gradient of Japan. The associated eye-of-the-typhoon tracks deviate notably and may thus distort estimates of heavy typhoon rainfall. We mainly found that the lower spread of rainfall tracks in ASON may enable better hindcasting than for westerly-fed frontal storms in June and July. Y1 - 2018 U6 - https://doi.org/10.1063/1.5004480 SN - 1054-1500 SN - 1089-7682 VL - 28 IS - 7 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Marwan, Norbert A1 - Nowaczyk, Norbert R. A1 - Kurths, Jürgen A1 - Thiel, Marco T1 - Cross recurrence plot based rescaling of geological time series N2 - The rescaling of geological data series to a geological reference time series is of major interest in many investigations. For example, geophysical borehole data should be correlated to a given data series whose time scale is known in order to achieve an age-depth function or the sedimentation rate for the borehole data. Usually this synchronization is performed visually and by hand. Instead of using this wiggle matching by eye, we present the application of cross recurrence plots for such tasks. Using this method, the synchronization and rescaling of geological data to a given time scale is much easier and faster than by hand. Y1 - 2001 SN - 1029-7006 ER - TY - JOUR A1 - Agarwal, Ankit A1 - Maheswaran, Rathinasamy A1 - Marwan, Norbert A1 - Caesar, Levke A1 - Kurths, Jürgen T1 - Wavelet-based multiscale similarity measure for complex networks JF - The European physical journal : B, Condensed matter and complex systems N2 - In recent years, complex network analysis facilitated the identification of universal and unexpected patterns in complex climate systems. However, the analysis and representation of a multiscale complex relationship that exists in the global climate system are limited. A logical first step in addressing this issue is to construct multiple networks over different timescales. Therefore, we propose to apply the wavelet multiscale correlation (WMC) similarity measure, which is a combination of two state-of-the-art methods, viz. wavelet and Pearson’s correlation, for investigating multiscale processes through complex networks. Firstly we decompose the data over different timescales using the wavelet approach and subsequently construct a corresponding network by Pearson’s correlation. The proposed approach is illustrated and tested on two synthetics and one real-world example. The first synthetic case study shows the efficacy of the proposed approach to unravel scale-specific connections, which are often undiscovered at a single scale. The second synthetic case study illustrates that by dividing and constructing a separate network for each time window we can detect significant changes in the signal structure. The real-world example investigates the behavior of the global sea surface temperature (SST) network at different timescales. Intriguingly, we notice that spatial dependent structure in SST evolves temporally. Overall, the proposed measure has an immense potential to provide essential insights on understanding and extending complex multivariate process studies at multiple scales. KW - Statistical and Nonlinear Physics Y1 - 2018 U6 - https://doi.org/10.1140/epjb/e2018-90460-6 SN - 1434-6028 SN - 1434-6036 VL - 91 IS - 11 PB - Springer CY - New York ER - TY - JOUR A1 - Marwan, Norbert A1 - Kurths, Jürgen T1 - Nonlinear analysis of bivariate data with cross recurrence plots N2 - We use the extension of the method of recurrence plots to cross recurrence plots (CRP) which enables a nonlinear analysis of bivariate data. To quantify CRPs, we develop further three measures of complexity mainly basing on diagonal structures in CRPs. The CRP analysis of prototypical model systems with nonlinear interactions demonstrates that this technique enables to find these nonlinear interrelations from bivariate time series, whereas linear correlation tests do not. Applying the CRP analysis to climatological data, we find a complex relationship between rainfall and El Nino data. Y1 - 2001 UR - http://arxiv.org/abs/physics/0201061 ER - TY - JOUR A1 - Wessel, Niels A1 - Marwan, Norbert A1 - Meyerfeldt, Udo A1 - Schirdewan, Alexander A1 - Kurths, Jürgen T1 - Recurrence quantification analysis to characterise the heart rate variability before the onset of ventricular tachycardia N2 - Ventricular tachycardia or fibrillation (VT) as fatal cardiac arrhythmias are the main factors triggering sudden cardiac death. The objective of this recurrence quantification analysis approach is to find early signs of sustained VT in patients with an implanted cardioverter-defibrillator (ICD). These devices are able to safeguard patients by returning their hearts to a normal rhythm via strong defibrillatory shocks; additionally, they are able to store at least 1000 beat-to-beat intervals immediately before the onset of a life-threatening arrhythmia. We study the Y1 - 2001 UR - http://link.springer.de/link/service/series/0558/bibs/2199/21990295.htm ER - TY - JOUR A1 - Marwan, Norbert A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Strecker, Manfred T1 - ENSO Impact on landslide generation in northwestern Argentina N2 - Climatic changes are of major importance in landslide generation in the Argentine Andes. Increased humidity as a potential influential factor was inferred from the temporal clustering of landslide deposits during a period of significantly wetter climate, 30,000 years ago. A change in seasonality was tested by comparing past (inferred from annual-layered lake deposits, 30,000 years old) and modern (present-day observations) precipitation changes. Quantitative analysis of cross recurrence plots were developed to compare the influence of the El Nino/Southern Oscillation (ENSO) on present and past rainfall variations. This analysis has shown the stronger influence of NE trades in the location of landslide deposits in the intra-andean basin and valleys, what caused a higher contrast between summer and winter rainfall and an increasing of precipitation in La Nina years. This is believed to reduce thresholds for landslide generation in the arid to semiarid intra-andean basins and valleys. Y1 - 2000 SN - 1029-7006 ER - TY - JOUR A1 - Marwan, Norbert A1 - Trauth, Martin H. A1 - Schwarz, Udo A1 - Kurths, Jürgen A1 - Strecker, Manfred T1 - Climate dynamics of varved pleistocene lake sediments in nw Argentina Y1 - 1999 SN - 1029-7006 ER - TY - JOUR A1 - Marwan, Norbert A1 - Kurths, Jürgen A1 - Thomsen, Jesper Skovhus A1 - Felsenberg, Dieter A1 - Saparin, Peter T1 - Three-dimensional quantification of structures in trabecular bone using measures of complexity N2 - The study of pathological changes of bone is an important task in diagnostic procedures of patients with metabolic bone diseases such as osteoporosis as well as in monitoring the health state of astronauts during long-term space flights. The recent availability of high-resolution three-dimensional (3D) imaging of bone challenges the development of data analysis techniques able to assess changes of the 3D microarchitecture of trabecular bone. We introduce an approach based on spatial geometrical properties and define structural measures of complexity for 3D image analysis. These measures evaluate different aspects of organization and complexity of 3D structures, such as complexity of its surface or shape variability. We apply these measures to 3D data acquired by high-resolution microcomputed tomography (mu CT) from human proximal tibiae and lumbar vertebrae at different stages of osteoporotic bone loss. The outcome is compared to the results of conventional static histomorphometry and exhibits clear relationships between the analyzed geometrical features of trabecular bone and loss of bone density, but also indicate that the measures reveal additional information about the structural composition of bone, which were not revealed by the static histomorphometry. Finally, we have studied the dependency of the developed measures of complexity on the spatial resolution of the mu CT data sets. Y1 - 2009 UR - http://pre.aps.org/ U6 - https://doi.org/10.1103/Physreve.79.021903 SN - 1539-3755 ER - TY - JOUR A1 - Zolotova, Nadezhda V. A1 - Ponyavin, Dmitri I. A1 - Marwan, Norbert A1 - Kurths, Jürgen T1 - Long-term asymmetry in the wings of the butterfly diagram N2 - Aims. Sunspot distribution in the northern and southern solar hemispheres exibit striking synchronous behaviour on the scale of a Schwabe cycle. However, sometimes the bilateral symmetry of the Butterfly diagram relative to the solar equatorial plane breaks down. The investigation of this phenomenon is important to explaining the almost-periodic behaviour of solar cycles. Methods. We use cross-recurrence plots for the study of the time-varying phase asymmetry of the northern and southern hemisphere and compare our results with the latitudinal distribution of the sunspots. Results. We observe a long-term persistence of phase leading in one of the hemispheres, which lasts almost 4 solar cycles and probably corresponds to the Gleissberg cycle. Long-term variations in the hemispheric-leading do not demonstrate clear periodicity but are strongly anti-correlated with the long-term variations in the magnetic equator. Y1 - 2009 UR - http://www.aanda.org/ U6 - https://doi.org/10.1051/0004-6361/200811430 SN - 0004-6361 ER - TY - JOUR A1 - Marwan, Norbert A1 - Kurths, Jürgen T1 - Comment on "Stochastic analysis of recurrence plots with applications to the detection of deterministic signals" by Rohde et al. : [Physica D 237 (2008) 619-629] N2 - In the recent article "Stochastic analysis of recurrence plots with applications to the detection of deterministic signals" (Physica D 237 (2008) 619-629), Rohde et al. stated that the performance of RQA in order to detect deterministic signals would be below traditional and well-known detectors. However, we have concerns about such a general statement. Based on our own studies we cannot confirm their conclusions. Our findings suggest that the measures of complexity provided by RQA are useful detectors outperforming well-known traditional detectors, in particular for the detection of signals of complex systems, with phase differences or signals modified due to the measurement process. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/01672789 U6 - https://doi.org/10.1016/j.physd.2009.04.018 SN - 0167-2789 ER - TY - JOUR A1 - Schinkel, Stefan A1 - Marwan, Norbert A1 - Dimigen, Olaf A1 - Kurths, Jürgen T1 - Confidence bounds of recurrence-based complexity measures N2 - In the recent past, recurrence quantification analysis (RQA) has gained an increasing interest in various research areas. The complexity measures the RQA provides have been useful in describing and analysing a broad range of data. It is known to be rather robust to noise and nonstationarities. Yet, one key question in empirical research concerns the confidence bounds of measured data. In the present Letter we suggest a method for estimating the confidence bounds of recurrence-based complexity measures. We study the applicability of the suggested method with model and real- life data. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/03759601 U6 - https://doi.org/10.1016/j.physleta.2009.04.045 SN - 0375-9601 ER - TY - JOUR A1 - Malik, Nishant A1 - Bookhagen, Bodo A1 - Marwan, Norbert A1 - Kurths, Jürgen T1 - Analysis of spatial and temporal extreme monsoonal rainfall over South Asia using complex networks JF - Climate dynamics : observational, theoretical and computational research on the climate system N2 - We present a detailed analysis of summer monsoon rainfall over the Indian peninsular using nonlinear spatial correlations. This analysis is carried out employing the tools of complex networks and a measure of nonlinear correlation for point processes such as rainfall, called event synchronization. This study provides valuable insights into the spatial organization, scales, and structure of the 90th and 94th percentile rainfall events during the Indian summer monsoon (June-September). We furthermore analyse the influence of different critical synoptic atmospheric systems and the impact of the steep Himalayan topography on rainfall patterns. The presented method not only helps us in visualising the structure of the extreme-event rainfall fields, but also identifies the water vapor pathways and decadal-scale moisture sinks over the region. Furthermore a simple scheme based on complex networks is presented to decipher the spatial intricacies and temporal evolution of monsoonal rainfall patterns over the last 6 decades. KW - Indian summer monsoon KW - Event synchronization KW - Complex networks KW - Rainfall patterns Y1 - 2012 U6 - https://doi.org/10.1007/s00382-011-1156-4 SN - 0930-7575 VL - 39 IS - 3-4 SP - 971 EP - 987 PB - Springer CY - New York ER - TY - JOUR A1 - Marwan, Norbert A1 - Beller, Gise A1 - Felsenberg, Dieter A1 - Saparin, Peter A1 - Kurths, Jürgen T1 - quantifying changes in the spatial structure of trabecular bone JF - International journal of bifurcation and chaos : in applied sciences and engineering N2 - We apply recently introduced measures of complexity for the structural quantification of distal tibial bone. For the first time, we are able to investigate the temporal structural alteration of trabecular bone. Based on four patients, we show how the bone may alter due to temporal immobilization. KW - 3D medical image analysis KW - pQCT KW - trabecular bone KW - patient immobilization Y1 - 2012 U6 - https://doi.org/10.1142/S0218127412500277 SN - 0218-1274 VL - 22 IS - 2 PB - World Scientific CY - Singapore ER - TY - JOUR A1 - Goswami, Bedartha A1 - Marwan, Norbert A1 - Feulner, Georg A1 - Kurths, Jürgen T1 - How do global temperature drivers influence each other? JF - European physical journal special topics N2 - We investigate a network of influences connected to global mean temperature. Considering various climatic factors known to influence global mean temperature, we evaluate not only the impacts of these factors on temperature but also the directed dependencies among the factors themselves. Based on an existing recurrence-based connectivity measure, we propose a new and more general measure that quantifies the level of dependence between two time series based on joint recurrences at a chosen time delay. The measures estimated in the analysis are tested for statistical significance using twin surrogates. We find, in accordance with earlier studies, the major drivers for global mean temperature to be greenhouse gases, ENSO, volcanic activity, and solar irradiance. We further uncover a feedback between temperature and ENSO. Our results demonstrate the need to involve multiple, delayed interactions within the drivers of temperature in order to develop a more thorough picture of global temperature variations. Y1 - 2013 U6 - https://doi.org/10.1140/epjst/e2013-01889-8 SN - 1951-6355 VL - 222 IS - 3-4 SP - 861 EP - 873 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Marwan, Norbert A1 - Schinkel, Stefan A1 - Kurths, Jürgen T1 - Recurrence plots 25 years later -Gaining confidence in dynamical transitions JF - epl : a letters journal exploring the frontiers of physics N2 - Recurrence-plot-based time series analysis is widely used to study changes and transitions in the dynamics of a system or temporal deviations from its overall dynamical regime. However, most studies do not discuss the significance of the detected variations in the recurrence quantification measures. In this letter we propose a novel method to add a confidence measure to the recurrence quantification analysis. We show how this approach can be used to study significant changes in dynamical systems due to a change in control parameters, chaos-order as well as chaos-chaos transitions. Finally we study and discuss climate transitions by analysing a marine proxy record for past sea surface temperature. This paper is dedicated to the 25th anniversary of the introduction of recurrence plots. Y1 - 2013 U6 - https://doi.org/10.1209/0295-5075/101/20007 SN - 0295-5075 VL - 101 IS - 2 PB - EDP Sciences CY - Mulhouse ER - TY - JOUR A1 - Schinkel, Stefan A1 - Marwan, Norbert A1 - Kurths, Jürgen T1 - Brain signal analysis based on recurrences N2 - The EEG is one of the most commonly used tools in brain research. Though of high relevance in research, the data obtained is very noisy and nonstationary. In the present article we investigate the applicability of a nonlinear data analysis method, the recurrence quantification analysis (RQA), to Such data. The method solely rests on the natural property of recurrence which is a phenomenon inherent to complex systems, such as the brain. We show that this method is indeed suitable for the analysis of EEG data and that it might improve contemporary EEG analysis. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/09284257 U6 - https://doi.org/10.1016/j.jphysparis.2009.05.007 SN - 0928-4257 ER - TY - JOUR A1 - Ozturk, Ugur A1 - Malik, Nishant A1 - Cheung, Kevin A1 - Marwan, Norbert A1 - Kurths, Jürgen T1 - A network-based comparative study of extreme tropical and frontal storm rainfall over Japan JF - Climate dynamics : observational, theoretical and computational research on the climate system N2 - Frequent and intense rainfall events demand innovative techniques to better predict the extreme rainfall dynamics. This task requires essentially the assessment of the basic types of atmospheric processes that trigger extreme rainfall, and then to examine the differences between those processes, which may help to identify key patterns to improve predictive algorithms. We employ tools from network theory to compare the spatial features of extreme rainfall over the Japanese archipelago and surrounding areas caused by two atmospheric processes: the Baiu front, which occurs mainly in June and July (JJ), and the tropical storms from August to November (ASON). We infer from complex networks of satellite-derived rainfall data, which are based on the nonlinear correlation measure of event synchronization. We compare the spatial scales involved in both systems and identify different regions which receive rainfall due to the large spatial scale of the Baiu and tropical storm systems. We observed that the spatial scales involved in the Baiu driven rainfall extremes, including the synoptic processes behind the frontal development, are larger than tropical storms, which even have long tracks during extratropical transitions. We further delineate regions of coherent rainfall during the two seasons based on network communities, identifying the horizontal (east-west) rainfall bands during JJ over the Japanese archipelago, while during ASON these bands align with the island arc of Japan. KW - Extreme rainfall KW - Baiu KW - Tropical storms KW - Event synchronization KW - Complex networks Y1 - 2019 U6 - https://doi.org/10.1007/s00382-018-4597-1 SN - 0930-7575 SN - 1432-0894 VL - 53 IS - 1-2 SP - 521 EP - 532 PB - Springer CY - New York ER -