Lagrangian study of the final warming in the southern stratosphere during 2002: Part I. The vortex splitting at upper levels

Jezabel Curbelo*, Carlos R. Mechoso, Ana M. Mancho, Stephen Wiggins

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

10 Citations (Scopus)


The present two-part paper provides a Lagrangian perspective of the final southern warming in 2002, during which the stratospheric polar vortex (SPV) experienced a unique splitting. Part I focuses on the understanding of fundamental processes for filamentation and ultimately for vortex splitting on a selected isentropic surface in the middle stratosphere. Part II discusses the three-dimensional evolution of the selected sudden warming event. We approach the subject from a dynamical systems viewpoint and search for Lagrangian coherent structures using a Lagrangian descriptor as a tool. In this Part I we work in the idealized framework of a kinematic model that allows for an understanding of the contributing elements of the flow in late September during the splitting. We introduce a definition of kinematic SPV boundary based on a criterion for binning parcels inside and outside the vortex according to their values of the Lagrangian descriptor and associated PDF. This definition is justified by using arguments that go beyond heuristic considerations based on the potential vorticity. Next, we turn to the filamentation processes along this kinematic boundary, and the role of Lagrangian structures in the SPV splitting. We determine a criterion for splitting based on the structure of the evolving unstable and unstable manifolds.

Original languageEnglish
Pages (from-to)2779-2792
Number of pages14
JournalClimate Dynamics
Issue number5-6
Publication statusPublished - 13 Sept 2019


  • Filamentation
  • Kinematic models
  • Stratospheric sudden warming
  • Vortex boundary
  • Vortex split


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