TY - JOUR

T1 - Spectral Early-Warning Signals for Sudden Changes in Time-Dependent Flow Patterns

AU - Ndour, Moussa

AU - Padberg-Gehle, Kathrin

AU - Rasmussen, Martin

N1 - Funding Information: Funding: This research has received funding from the European Union’s Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie grant agreement No. 643073 (ITN CRITICS) as well as from the Deutsche Forschungsgemeinschaft within the Priority Program SPP 1881 Turbulent Superstructures (PA1972/3-2). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2021/2

Y1 - 2021/2

N2 - Lagrangian coherent sets are known to crucially determine transport and mixing processes in non-autonomous flows. Prominent examples include vortices and jets in geophysical fluid flows. Coherent sets can be identified computationally by a probabilistic transfer-operator-based approach within a set-oriented numerical framework. Here, we study sudden changes in flow patterns that correspond to bifurcations of coherent sets. Significant changes in the spectral properties of a numerical transfer operator are heuristically related to critical events in the phase space of a time-dependent system. The transfer operator approach is applied to different example systems of increasing complexity. In particular, we study the 2002 splitting event of the Antarctic polar vortex.

AB - Lagrangian coherent sets are known to crucially determine transport and mixing processes in non-autonomous flows. Prominent examples include vortices and jets in geophysical fluid flows. Coherent sets can be identified computationally by a probabilistic transfer-operator-based approach within a set-oriented numerical framework. Here, we study sudden changes in flow patterns that correspond to bifurcations of coherent sets. Significant changes in the spectral properties of a numerical transfer operator are heuristically related to critical events in the phase space of a time-dependent system. The transfer operator approach is applied to different example systems of increasing complexity. In particular, we study the 2002 splitting event of the Antarctic polar vortex.

KW - Lagrangian transport

KW - bifurcation

KW - coherent set

KW - probabilistic approach

KW - singular value decomposition

KW - transfer operator

KW - Mathematics

UR - http://www.scopus.com/inward/record.url?scp=85104399176&partnerID=8YFLogxK

U2 - 10.3390/fluids6020049

DO - 10.3390/fluids6020049

M3 - Journal articles

VL - 6

JO - Fluids

JF - Fluids

SN - 2311-5521

IS - 2

M1 - 49

ER -