Modeling rossby wave breaking in the southern spring stratosphere

Anirban Guha (Lead / Corresponding author), Carlos R. Mechoso, Celal S. Konor, Ross P. Heikes

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Rossby wave breaking (RWB) plays a central role in the evolution of stratospheric flows. The generation and evolution of RWB is examined in the simple dynamical framework of a one-layer shallow-water system on a sphere. The initial condition represents a realistic, zonally symmetric velocity profile corresponding to the springtime southern stratosphere. Single zonal wavenumber Rossby waves, which are either stationary or traveling zonally with realistic speeds, are superimposed on the initial velocity profile. Particular attention is placed on the Lagrangian structures associated with RWB. The Lagrangian analysis is based on the calculation of trajectories and the application of a diagnostic tool known as the "M" function. Hyperbolic trajectories (HTs), produced by the transverse intersections of stable and unstable invariant manifolds, may yield chaotic saddles inM. Previous studies associated HTs with "cat's eyes" generated by planetary wave breaking at the critical levels. HTs, and hence RWB, are found both outside and inside the stratospheric polar vortex (SPV). Significant findings are as follows: (i) stationary forcing produces HTs only outside of the SPV and (ii) eastward-traveling wave forcing can produce HTs both outside and inside of the SPV. In either case, HTs appear at or near the critical latitudes. RWB was found to occur inside the SPV even when the forcing was located completely outside. In all cases, the westerly jet remained impermeable throughout the simulations. The results suggest that the HT inside the SPV observed by de la Cámara et al. during the southern spring 2005 was due to RWB of an eastward-traveling wave of wavenumber 1.

Original languageEnglish
Pages (from-to)393-406
Number of pages14
JournalJournal of the Atmospheric Sciences
Volume73
Issue number1
Early online date30 Dec 2015
DOIs
Publication statusPublished - Jan 2016

Keywords

  • Circulation/Dynamics
  • Rossby waves
  • Atm/Ocean Structure/Phenomena
  • Middle atmosphere
  • Stratosphere
  • Vortices
  • Models and modeling
  • Tracers

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