Articles | Volume 9, issue 3/4
Nonlin. Processes Geophys., 9, 265–279, 2002
https://doi.org/10.5194/npg-9-265-2002
Nonlin. Processes Geophys., 9, 265–279, 2002
https://doi.org/10.5194/npg-9-265-2002

  31 Aug 2002

31 Aug 2002

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

D. Berson1 and Z. Kizner1,2 D. Berson and Z. Kizner
  • 1Department of Physics, Bar-Ilan University, Ramat-Gan 52900, Israel
  • 2Department of Mathematics, Bar-Ilan University, Ramat-Gan 52900, Israel

Abstract. 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.