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Detalhes Referência

Tipo
Artigos em Conferência

Tipo de Documento
Resumo

Título
Bicovariance and Bispectrum of ENSO index and its impact in nonlinear predictability 

Participantes na publicação
Carlos Pires (Author)
Dep. Engenharia Geográfica, Geofísica e Energia
 IDL
 Abdel Hannach (Author)

Resumo
El Niño Southern Oscillation (ENSO) index has been shown as a non-Gaussian and nonlinear stochastic process. Here we assess the statistical significance of non-Gaussianity and non-linearity through the analysis of third-order statistics of El Niño 3.4 index in the period 1870–2018, namely the bicovariance (lagged third-order moments) and bispectrum (its 2D Fourier transform). The analysis of bicovariance reveals a tendency for extreme (weak) ENSO signal in the Boreal Spring to be followed by la Niñas (El Niños) in the forthcoming Boreal Winter, thus contributing for a nonlinear attenuation of the ENSO Spring Predictability Barrier. The bispectrum provides a spectral decomposition of skewness in a similar way of the spectral decomposition of variance. Positive and negative real bispectrum values identify triadic phase synchronizations (at frequencies f1, f2 and f1+f2, mostly in the period range 2–6 years) contributing respectively to extreme El Niños and La Niñas. The known positive ENSO skewness and the main features of the ENSO bicovariance and bispectrum are shown to be well reproduced by fitting a bilinear stochastic model where the influence of non-observed variables is simulated by a delayed multiplicative noise, being able to generate non-Gaussianity and non-linearity. The model shows improved forecasts, with respect to benchmark linear models, up to four trimesters ahead, especially of the amplitude of extreme El Niños. The authors would like to acknowledge MISU (Meteorological Institute at Stockholm University) and the financial support FCT through project UIDB/50019/2020 – IDL and project JPIOCEANS/0001/2019 (ROADMAP: ’The Role of ocean dynamics and Ocean–Atmosphere interactions in Driving cliMAte variations and future Projections of impact–relevant extreme events’).

Data de Submissão/Pedido
2021-03-04
Data de Aceitação
2021-03-04
Data de Publicação
2021-03-04

Instituição
UNIVERSIDADE DE LISBOA

Evento
EGU General Assembly 2021, online

Identificadores da Publicação

Editora
Copernicus GmbH

Identificadores do Documento
DOI - https://doi.org/10.5194/egusphere-egu21-8439
URL - http://dx.doi.org/10.5194/egusphere-egu21-8439


Exportar referência

APA
Carlos Pires, Abdel Hannach, (2021). Bicovariance and Bispectrum of ENSO index and its impact in nonlinear predictability . EGU General Assembly 2021, online, -

IEEE
Carlos Pires, Abdel Hannach, "Bicovariance and Bispectrum of ENSO index and its impact in nonlinear predictability " in EGU General Assembly 2021, online, , 2021, pp. -, doi: 10.5194/egusphere-egu21-8439

BIBTEX
@InProceedings{55746, author = {Carlos Pires and Abdel Hannach}, title = {Bicovariance and Bispectrum of ENSO index and its impact in nonlinear predictability }, booktitle = {EGU General Assembly 2021, online}, year = 2021, pages = {-}, address = {}, publisher = {Copernicus GmbH} }