Contraction of westward-travelling nonlocal modons due to the vorticity filament emission

Long-term evolution of westward-travelling non-local modons on the β-plane, i.e. dipolar vortices imbedded in slowly damping Rossby wave fields, is studied numerically. In the framework of the nondivergent (barotropic) model, two stages of the evolution are observed. At the first stage (for about 30...

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Bibliographic Details
Published in:Nonlinear processes in geophysics 2002, Vol.9 (3/4), p.265-279
Main Authors: Berson, D., Kizner, Z.
Format: Article
Language:English
Subjects:
Astrophysics
Cosmology and Extra-Galactic Astrophysics
Earth Sciences
Physics
Sciences of the Universe
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Summary:Long-term evolution of westward-travelling non-local modons on the β-plane, i.e. dipolar vortices imbedded in slowly damping Rossby wave fields, is studied numerically. In the framework of the nondivergent (barotropic) model, two stages of the evolution are observed. At the first stage (for about 30 synoptic periods), the parameters and the form of the vortex practically remain constant, whereas at the second stage, vorticity filaments are emitted. Due to the filamentation, the vortex core contracts, the potential vorticity peaks of the vortex pair get closer, and the modon speeds up. In the divergent (equivalent-barotropic) model, nonlocal modons and the Lamb modon (that has no wave field outside the dipolar core) evolve much more slowly, essentially preserving the initial shape and propagation speed until about 100 synoptic periods.
ISSN:1607-7946
1023-5809
1607-7946
DOI:10.5194/npg-9-265-2002