Kurths, J.

Loew, A.

Marwan, N.

Oluoch, K.

Trauth, M.

English

MPG.PuRe

Geophysical Research AbstractsVol. 14, EGU2012-11674-3, 2012EGU General Assembly 2012© Author(s) 2012Complex Networks Dynamics Based on Events-Phase Synchronizationand Intensity Correlation Applied to The Anomaly Patterns and Extremesin The Tropical African Climate SystemK. Oluoch (1,2), N. Marwan (2), M. Trauth (1), A. Loew (3), and J. Kurths (2)(1) University of Potsdam, Institute of Earth and Environmental Science, Graduate School GRK1364, Berlin, Germany(oluoch@pik-potsdam.de)., (2) Potsdam Institute for Climate Impact Research, Research Domain IV: TransdisciplinaryConcepts and Methods, Potsdam, Germany., (3) Max Planck Institute for Meteorology, Hamburg, Germany.The African continent lie almost entirely within the tropics and as such its (tropical) climate systems arepredominantly governed by the heterogeneous, spatial and temporal variability of the Hadley and Walkercirculations. The variabilities in these meridional and zonal circulations lead to intensification or suppression ofthe intensities, durations and frequencies of the Inter-tropical Convergence Zone (ICTZ) migration, trade windsand subtropical high-pressure regions and the continental monsoons. The above features play a central role indetermining the African rainfall spatial and temporal variability patterns. The current understanding of theseclimate features and their influence on the rainfall patterns is not sufficiently understood. Like many real-worldsystems, atmospheric-oceanic processes exhibit non-linear properties that can be better explored using non-linear(NL) methods of time-series analysis.Over the recent years, the complex network approach has evolved as a powerful new player in understand-ing spatio-temporal dynamics and evolution of complex systems. Together with NL techniques, it is continuingto find new applications in many areas of science and technology including climate research. We would like touse these two powerful methods to understand the spatial structure and dynamics of African rainfall anomalypatterns and extremes. The method of event synchronization (ES) developed by Quiroga et al., 2002 and firstapplied to climate networks by Malik et al., 2011 looks at correlations with a dynamic time lag and as such, itis a more intuitive way to correlate a complex and heterogeneous system like climate networks than a fixed timedelay most commonly used. On the other hand, the short comings of ES is its lack of vigorous test statistics forthe significance level of the correlations, and the fact that only the events’ time indices are synchronized while allinformation about how the relative intensities propagate within network framework is lost.The new method we present is motivated by the ES and borrows ideas from signal processing where a sig-nal is represented by its intensity and frequency. Even though the anomaly signals are not periodic, the idea ofphase synchronization is not far fetched. It brings into one umbrella, the traditionally known linear Intensitycorrelation methods like Pearson correlation, spear-man’s rank or non-linear ones like mutual information withthe ES for non-linear temporal synchronization. The intensity correlation is only performed where there is atemporal synchronization. The former just measures how constant the intensity differences are. In other words,how monotonic are the two functions. The overall measure of correlation and synchronization is the product of thetwo coefficients. Complex networks constructed by this technique has all the advantages inherent in each of thetechniques it borrows. But, it is more superior and able to uncover many known and unknown dynamical featuresin rainfall field or any variable of interest. The main aim of this work is to develop a method that can identifythe footprints of coherent or incoherent structures within the ICTZ, the African and the Indian monsoons and theENSO signal on the tropical African continent and their temporal evolution.

Complex networks dynamics based on events-phase synchronization and intensity correlation applied to the anomaly patterns and extremes in the tropical African climate system

Complex networks dynamics based on events-phase synchronization and intensity correlation applied to the anomaly patterns and extremes in the tropical African climate system

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