El Aouni, Anass

Vidard, Arthur

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Keywords:Life-time independent approach to Lagrangian vortices detection *Anass El Aouni1, Arthur Vidard1 1. INRIA/LJK Grenoble, France Lagrangian coherent structures (LCSs) are differentiated surfaces of trajectories in a dynamical systemthat exert significant effects on adjacent trajectories over a finite-time interval. These LCSs are mainlystructured into three physical shapes, in the geophysical fluid dynamics field these structures are referredto as mesoscale and submesoscale filaments, jets and eddies. These latter structures are omnipresent inthe ocean and usually exhibit different properties to their surroundings. They are known to stir and mixsurroundings water masses as well as by their ability to trap and carry water properties in a coherentmanner. In the present work, we are interested in those that remain coherent despite their chaoticenvironment. Such mesoscale eddies have an important role to play in climate change arising from theirinfluence on the circulation by transporting temperature and salinity. As these mesoscale eddies have aremarkable impact on the global circulation, their systematic and precise detection has been of greatconcern over the last decade. Several Lagrangian vortex definitions have been introduced in the literaturetogether with their automatic detection. Indeed, These methods identify and extract such eddies in a verycoherent manner. However, they suffer from a conceptual point of view; they all require the sought eddieslife-time to be exactly equal to the time interval of particles’ advection. For example, by choosing a timeinterval of six months, such methods only extract eddies that do exist and remain coherent exactly sixmonths. Thus, these methods miss several eddies that have existed within the time interval of advectionbut have life-times different from 6 months. In the present work, we present a life-time independentmethod that is able to lump eddies occurring over different time intervals into the same scalar field. Here,we reveal that such eddies can be identified based on the frequency-domain representation of theirtrajectories. We then identify and extract coherent vortices as material surfaces along which particles’trajectories share similar frequency components and life-time. The present method identifies all coherenteddies in an automatic manner, showing high eddies’ monitoring capacity. We illustrate our new methodby identifying and extracting Lagrangian coherent eddies in different fluid flows. Lagrangian coherent structures , Vortex dynamics, Mesoscale eddies, Lagrangian vortexdetection, Coherent water transport AOS21-10 JpGU-AGU Joint Meeting 2020- AOS21-10 -AOS21-10 JpGU-AGU Joint Meeting 2020- AOS21-10 -

Life-time independent approach to Lagrangian vortices detection

https://hal.inria.fr/hal-03482804v1/file/AOS21-10%20%281%29.pdf

Life-time independent approach to Lagrangian vortices detection

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