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On the Dynamics Underlying the Emergence of Coherent Structures in Barotropic Turbulence

  • N. A. Bakas
  • N. C. Constantinou
  • P. J. Ioannou
Conference paper
Part of the Springer Atmospheric Sciences book series (SPRINGERATMO)

Abstract

Planetary turbulent flows are observed to self-organize into large scale structures such as zonal jets and coherent vortices. In this work, the eddy-mean flow dynamics underlying the formation of both zonal and nonzonal coherent structures in a barotropic turbulent flow is investigated within the statistical framework of stochastic structural stability theory (S3T). Previous studies have shown that the coherent structures emerge due to the instability of the homogeneous turbulent flow in the statistical dynamical S3T system and that the statistical predictions of S3T are reflected in direct numerical simulations. In this work, the dynamics underlying the structure forming S3T instability are studied. It is shown that, for weak planetary vorticity gradient beta, both zonal jets and non-zonal large-scale structures form from upgradient momentum fluxes due to shearing of the eddies by the emerging flow. For large beta, the dynamics of the S3T instability differs for zonal and non-zonal flows. Shearing of the eddies by the mean flow continues to be the mechanism for the emergence of zonal jets while non-zonal large-scale flows emerge from resonant and near-resonant triad interactions between the large-scale flow and the stochastically forced eddies.

Keywords

Direct Numerical Simulation Coherent Structure Rossby Wave Momentum Flux Relative Vorticity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

N. Bakas is supported by the AXA Research Fund and N. Constantinou is partially supported by the NOAA Climate and Global Change Postdoctoral Fellowship Program, administered by UCAR’s Visiting Scientist Programs.

References

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Copyright information

© Springer International Publishing Switzerland 2017

Authors and Affiliations

  • N. A. Bakas
    • 1
  • N. C. Constantinou
    • 2
  • P. J. Ioannou
    • 3
  1. 1.Laboratory of Meteorology, Department of PhysicsUniversity of IoanninaIoanninaGreece
  2. 2.Scripps Institution of OceanographyUniversity of CaliforniaSan DiegoUSA
  3. 3.Department of PhysicsNational and Kapodistrian University of AthensAthensGreece

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