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5 results on '"Viennet, Akim"'

2. Guidelines for data-driven approaches to study transitions in multiscale systems: the case of Lyapunov vectors

Author

Viennet, Akim, Vercauteren, Nikki, Engel, Maximilian, and Faranda, Davide

Subjects
Mathematics - Dynamical Systems, 37N10 (Primary) 86A08, 86A10 (Secondary)
Abstract

We study in detail the role of covariant Lyapunov vectors and their respective angles for detecting transitions between metastable states in dynamical systems, as recently discussed in several atmospheric science applications. The underlying models are built from data by the dynamical clustering method, called FEM-BV-VAR, and the Lyapunov vectors are approximated based on these models. We test this data-based numerical approach at the hand of three well-understood example systems with increasing dynamical complexity, identifying crucial properties that allow for a successful application of the method: in particular, it turns out that the method requires a clear multiple time scale structure with fast transitions between slow subsystems which can be dynamically characterized by invariant neutral directions of the linear approximation model.

Published
2022
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5. Decrease of the dynamical and spatial variability of the Euro-Atlantic eddy-driven jet stream with global warming

Author

Noyelle, Robin, Guette, Vivien, Viennet, Akim, Faranda, Davide, Extrèmes : Statistiques, Impacts et Régionalisation (ESTIMR), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), London Mathematical Laboratory, European Project: 101003469,XAIDA, and European Project: 956396,EDIPI

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, inter-decadal variability, causal analysis, jet stream, global warming
Abstract

The atmospheric eddy-driven jet stream is one of the main features of the mid-latitude circulation. Although mostly zonal in climatological mean, the jet stream meanders at meteorological time scales. The jet and its variability have been under great scrutiny in the past years for their role in the triggering of extreme events (e.g. heat or cold waves) in mid-latitudes regions. Because of the large variability of the jet, the impact of climate change remains elusive. Here we study the eddy-driven jet stream over the Euro-Atlantic sector and assess its dynamical properties in ERA5 and ERA20C reanalysis data set using indicators from dynamical system theory. We then use a causal framework to disentangle the impact of global warming from the impact of natural variability of the climate system on the jet. We find that over the period 1900-2010, global warming decreased the spatial and dynamical variability of the jet. This decrease in variability is connected to an increase in jet persistence and speed. We additionally observe a poleward shift of the jet. Our results suggest a zonalisation of the jet under global warming.

Published
2021

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