@article{fdi:010048189,
title = {{ENSO}'s non-stationary and non-{G}aussian character : the role of climate shifts},
author = {{B}oucharel, {J}. and {D}ewitte, {B}oris and {G}arel, {B}. and {P}enhoat, {Y}ves du},
language = {{ENG}},
abstract = {{E}l {N}ino {S}outhern {O}scillation ({ENSO}) is the dominant mode of climate variability in the {P}acific, 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). {S}ome 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 {G}aussian distribution. {T}hese properties could be related to the ability of the current generation of coupled models to predict {ENSO} and its modulation. {H}ere, {ENSO}'s non-{G}aussian 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 ({CGCM}s)) using robust statistical tools initially designed for financial mathematics studies. {I}n particular alpha-stable laws are used as theoretical background material to measure (and quantify) the non-{G}aussian character of {ENSO} time series and to estimate the skill of "naive" statistical models in producing deviation from {G}aussian laws and asymmetry. {T}he former are based on non-stationary processes dominated by abrupt changes in mean state and empirical variance. {I}t is shown that the alpha-stable character of {ENSO} may result from the presence of climate shifts in the time series. {A}lso, cool (warm) periods are associated with {ENSO} statistics having a stronger (weaker) tendency towards {G}aussianity and lower (greater) asymmetry. {T}his supports the hypothesis of {ENSO} being rectified by changes in mean state through nonlinear processes. {T}he relationship between changes in mean state and nonlinearity (skewness) is further investigated both in the {Z}ebiak and {C}ane (1987)'s model and the models of the {I}ntergovernmental {P}anel for {C}limate {C}hange ({IPCC}). {W}hereas there is a clear relationship in all models between {ENSO} asymmetry (as measured by skewness or nonlinear advection) and changes in mean state, they exhibit a variety of behaviour with regard to alpha-stability. {T}his suggests that the dynamics associated with climate shifts and the occurrence of extreme events involve higher-order statistical moments that cannot be accounted for solely by nonlinear advection.},
keywords = {},
journal = {{N}onlinear {P}rocesses in {G}eophysics},
volume = {16},
numero = {4},
pages = {453--473},
ISSN = {1023-5809},
year = {2009},
URL = {http://www.documentation.ird.fr/hor/fdi:010048189},
}