Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 16 4 2009 10.5194/npg-16-453-2009 http://www.nonlin-processes-geophys.net/16/453/2009/ http://www.nonlin-processes-geophys.net/16/453/2009/npg-16-453-2009.html http://www.nonlin-processes-geophys.net/16/453/2009/npg-16-453-2009.pdf 453 473 2009-07-06 ENSO's non-stationary and non-Gaussian character: the role of climate shifts J. Boucharel julien.boucharel@legos.obs-mip.fr B. Dewitte B. Garel Y. du Penhoat Université de Toulouse, UPS, LEGOS, 14 Av, Edouard Belin, 31400 Toulouse, France IRD, LEGOS, 31400 Toulouse, France IMARPE, Callao, Peru Université de Toulouse, INP-ENSEEIHT, UPS, Institut de Mathématiques de Toulouse, France El Niño Southern Oscillation (ENSO) is the dominant mode of climate variability in the Pacific, having socio-economic impacts on surrounding regions. ENSO exhibits significant modulation on decadal to inter-decadal time scales which is related to changes in its characteristics (onset, amplitude, frequency, propagation, and predictability). Some of these characteristics tend to be overlooked in ENSO studies, such as its asymmetry (the number and amplitude of warm and cold events are not equal) and the deviation of its statistics from those of the Gaussian distribution. These properties could be related to the ability of the current generation of coupled models to predict ENSO and its modulation. <br><br> Here, ENSO's non-Gaussian nature and asymmetry are diagnosed from in situ data and a variety of models (from intermediate complexity models to full-physics coupled general circulation models (CGCMs)) using robust statistical tools initially designed for financial mathematics studies. 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