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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/npg-2017-36
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
28 Jul 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Nonlinear Processes in Geophysics (NPG).
Dynamical properties and extremes of Northern Hemisphere climate fields over the past 60 years
Davide Faranda1, Gabriele Messori2,a, M. Carmen Alvarez-Castro1, and Pascal Yiou1 1LSCE-IPSL, CEA Saclay l'Orme des Merisiers, CNRS UMR 8212 CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
2Department of Meteorology, Stockholm University and Bolin Centre for Climate Science, Stockholm, Sweden
acurrently at: visiting researcher at LSCE-IPSL, CEA Saclay l'Orme des Merisiers, CNRS UMR 8212 CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
Abstract. Atmospheric dynamics is described by a set of partial differential equation yielding an infinite dimensional phase space. However, the actual trajectories followed by the system appear to be constrained to a finite dimensional phase space, i.e. a strange attractor. The dynamical properties of this attractor are difficult to determine due to the complex nature of atmospheric motions. A first step to simplify the problem is to focus on observables which affect – or are linked to phenomena which affect – human welfare and activities, such as sea level pressure, near-surface temperature and precipitation. We make use of recent advances in dynamical systems theory to estimate two instantaneous dynamical properties of the above fields for the Northern Hemisphere: local dimension and persistence. We then use these metrics to characterise the seasonality of the different fields and their interplay. We further analyse the large-scale anomaly patterns corresponding to phase-space extremes – namely timesteps at which the fields display extremes in their instantaneous dynamical properties. The analysis is based on the NCEP/NCAR reanalysis data, over the period 1948–2013. The results show that: (i) despite the high dimensionality of atmospheric dynamics, the Northern Hemisphere sea level pressure and temperature fields can on average be described by roughly twenty degrees of freedom; (ii) the precipitation field has a higher dimensionality; (iii) the seasonal forcing modulates the variability of the dynamical indicators and affects the occurrence of phase-space extremes. We further identify a number of robust correlations between the dynamical properties of the different variables.

Citation: Faranda, D., Messori, G., Alvarez-Castro, M. C., and Yiou, P.: Dynamical properties and extremes of Northern Hemisphere climate fields over the past 60 years, Nonlin. Processes Geophys. Discuss., https://doi.org/10.5194/npg-2017-36, in review, 2017.
Davide Faranda et al.
Davide Faranda et al.
Davide Faranda et al.

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