EGU2020-13481
https://doi.org/10.5194/egusphere-egu2020-13481
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Nonlinear time series models for the North Atlantic Oscillation

Abdel Hannachi1, Thomas Önskog2, and Christian Franzke3
Abdel Hannachi et al.
  • 1University of Stockholm, Department of Meteorology, MISU, Stockholm, Sweden (a.hannachi@misu.su.se)
  • 2Department of Mathematics, KTH Royal Institute of Technology, Stockholm, Sweden
  • 3Meteorological Institute and Center for Earth System Research and Sustainability, University of Hamburg, Hamburg, Germany

The North Atlantic Oscillation (NAO) is the dominant mode of climate variability over the North Atlantic basin and has a significant impact on seasonal climate and surface weather conditions. This is the result of complex and nonlinear interactions between many spatio-temporal scales. Here, the authors study a number of linear and nonlinear models for a station-based time series of the daily winter NAO index. It is found that nonlinear autoregressive models including both short and long lags perform excellently in reproducing the characteristic statistical properties of the NAO, such as skewness and fat tails of the distribution and the different time scales of the two phases. As a spinoff of the modelling procedure, we are able to deduce that the interannual dependence of the NAO mostly affects the positive phase and that timescales of one to three weeks are more dominant for the negative phase. The statistical properties of the model makes it useful for the generation of realistic climate noise.

How to cite: Hannachi, A., Önskog, T., and Franzke, C.: Nonlinear time series models for the North Atlantic Oscillation, EGU General Assembly 2020, Online, 4–8 May 2020, https://doi.org/10.5194/egusphere-egu2020-13481, 2020

Comments on the presentation

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Presentation version 1 – uploaded on 02 Apr 2020
  • CC1: Comment on EGU2020-13481, Paul Pukite, 06 May 2020

    The NAO time-series appears to have the same common-mode basis as ENSO, in being driven by a lunisolar tidal forcing

    • AC2: Reply to CC1, Abdel Hannachi, 06 May 2020

      Thanks Paul for this interesting comment!

      We did not look at the spectra of the NAO, we msotly looked at the time domain focussing on the nonlinear aspect of predictability.  The lunisolar forcing seems to be all over (NAO, Arctic Oscillation, plant growth ...).   which frequency precisely you are talking about - From the figure you posted, you seem to tal about quite low frequency, righ!

      /Abdel

       

      • CC2: Reply to AC2, Paul Pukite, 09 May 2020

        Yes these are monthly tidal frequencies,  monthly & fortnightly, but they are amplified by the annual and semiannual impulses which leads to aliased periodicties on the order of a few years.  This aliasing makes it difficult to associate NAO periods to tidal periods. We presented this at the AGU recently

        • AC3: Reply to CC2, Abdel Hannachi, 10 May 2020

          Thanks Paul for the clarification.

          Is is possible to share your AGU  paper/presentation?

          Best wishes

          Abdel Hannachi

          • CC3: Reply to AC3, Paul Pukite, 10 May 2020

            I tried once, it looks like embedded links are stripped in comments. So here is a plain text link  https://www.essoar.org/doi/10.1002/essoar.10500568.1

             

  • AC1: Comment on EGU2020-13481, Abdel Hannachi, 06 May 2020

    Thanks Paul for this interesting comment!

    We did not look at the spectra of the NAO, we msotly looked at the time domain focussing on the nonlinear aspect of predictability.  The lunisolar forcing seems to be all over (NAO, Arctic Oscillation, plant growth ...).   which frequency precisely you are talking about - From the figure you posted, you seem to tal about quite low frequency, righ!

    /Abdel