Time–Frequency Variability of ENSO and Stochastic Simulations
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In this article, the authors analyzed changes of the spectrum with time of three ENSO indices: the conventional Southern Oscillation index (SOI), Nino3 sea surface temperatures, and a tropical Pacific rain index, over the period 1871-1995.Abstract:
The time-frequency spectral structure of El Nino-Southern Oscillation (ENSO) time series holds much information about the physical dynamics of the ENSO system. The authors have analyzed changes of the spectrum with time of three ENSO indices: the conventional Southern Oscillation index (SOI), Nino3 sea surface temperatures, and a tropical Pacific rain index, over the period 1871-1995. Three methods of time-frequency analysis-windowed Fourier transform, wavelet analysis, and windowed Prony's method-were used, and the results are in good agreement. The time-frequency spectra of all the series show strong multidecadal variations over the past century. In particular, there was reduced activity of ENSO in the 2-3-yr periodicity range during the period 1920-60, compared with both the earlier and later periods. The dominant frequencies in the spectra do not appear to be constrained to certain frequency bands, and there is no evidence that the ENSO system has fixed modes of oscillation. The qualitative behavior of the real SOI time series has been compared with that of time series simulated by an autoregressive stochastic process of order 3 and time series created by phase-randomizing the spectral components of the SOI. The decadal variability of the amplitude and time-frequency spectra was found to be very similar between the observed and simulated SOIs. This suggests that the decadal variability of ENSO can be well simulated by a stochastic model and that stochastic forcing may be an important component of ENSO dynamics.read more
Citations
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A Practical Guide to Wavelet Analysis.
TL;DR: In this article, a step-by-step guide to wavelet analysis is given, with examples taken from time series of the El Nino-Southern Oscillation (ENSO).
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Interdecadal changes in the ENSO-monsoon system
TL;DR: In this paper, wavelet analysis is applied to indexes of equatorial Pacific sea surface temperature (Nino3 SST), the Southern Oscillation index, and all-India rainfall.
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Observed climate variability and change
TL;DR: In this paper, the authors emphasise that the certainty of conclusions that can be drawn about climate from observations depends critically on the availability of accurate, complete and consistent series of observations.
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Improved analyses of changes and uncertainties in sea surface temperature measured in Situ since the mid-nineteenth century: The HadSST2 dataset
Nick Rayner,Philip Brohan,David E. Parker,Chris K. Folland,John Kennedy,Michael Vanicek,T. J. Ansell,Simon F. B. Tett +7 more
TL;DR: The Second Hadley Centre Sea Surface Temperature dataset (HadSST2) as mentioned in this paper is based on data contained within the recently created International Comprehensive Ocean-Atmosphere Data Set (ICOADS) database and has smaller uncertainties.
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Cross wavelet analysis: significance testing and pitfalls
Douglas Maraun,Jürgen Kurths +1 more
TL;DR: It is shown that coherency between ENSO and NAO is an artefact for most of the time from 1900 to 1995, however, during a distinct period from around 1920 to 1940, significant co herency between the two phenomena occurs.
References
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Journal ArticleDOI
Wavelet Transforms and their Applications to Turbulence
TL;DR: Wavelet transforms are recent mathematical techniques, based on group theory and square integrable representations, which allows one to unfold a signal, or a field, into both space and scale, and possibly directions.
Journal ArticleDOI
Variations in Tropical Sea Surface Temperature and Surface Wind Fields Associated with the Southern Oscillation/El Niño
TL;DR: In this article, the evolution of sea surface temperature (SST) anomalies, surface wind fields, and precipitation anomaly patterns during major warm episodes in the eastern and central tropical Pacific are described in terms of composite SST and wind fields (30°N−30°S) for six warm episodes since 1949, and time series and cross-spectral analyses of mean monthly data along six shipping lanes which cross the equator between the South American coast and 170°W.
Journal ArticleDOI
The Optimal Growth of Tropical Sea Surface Temperature Anomalies
TL;DR: In this paper, it is argued from SST observations for the period 1950-90 that the tropical Indo-Pacific ocean-atmosphere system may be described as a stable linear dynamical system driven by spatially coherent Gaussian white noise.
Journal ArticleDOI
Climate Signal Detection Using Wavelet Transform: How to Make a Time Series Sing
K.-M. Lau,Hengyi Weng +1 more
TL;DR: In this paper, the application of the wavelet transform (WT) to climate time series analyses is introduced, and a tutorial description of the basic concept of WT compared with similar concepts used in music is also provided.
Journal ArticleDOI
An introduction to wavelet analysis in oceanography and meteorology - With application to the dispersion of Yanai waves
TL;DR: In this article, the dispersion of Yanai waves in a reduced gravity equatorial model is studied and the usefulness of the wavelet transform is demonstrated by measuring the group velocity directly over a finite range of wavenumbers by examining the time evolution of the transform.