A simple kinematic model for the Lagrangian description of relevant nonlinear processes in the stratospheric polar vortex
- 1Instituto de Ciencias Matemáticas, CSIC-UAM-UC3M-UCM, C/ Nicolás Cabrera 15, Campus de Cantoblanco UAM, 28049 Madrid, Spain
- 2Departamento de Matemáticas, Facultad de Ciencias, Universidad Autonóma de Madrid, Madrid, Spain
- 3Department of Atmospheric and Oceanic Sciences, University of California at Los Angeles, Los Angeles, CA, USA
- 4School of Mathematics, University of Bristol, Bristol, UK
Abstract. In this work, we study the Lagrangian footprint of the planetary waves present in the Southern Hemisphere stratosphere during the exceptional sudden Stratospheric warming event that took place during September 2002. Our focus is on constructing a simple kinematic model that retains the fundamental mechanisms responsible for complex fluid parcel evolution, during the polar vortex breakdown and its previous stages. The construction of the kinematic model is guided by the Fourier decomposition of the geopotential field. The study of Lagrangian transport phenomena in the ERA-Interim reanalysis data highlights hyperbolic trajectories, and these trajectories are Lagrangian objects that are the kinematic mechanism for the observed filamentation phenomena. Our analysis shows that the breaking and splitting of the polar vortex is justified in our model by the sudden growth of a planetary wave and the decay of the axisymmetric flow.