Lagrangian approach to geostrophic adjustment of frontal anomalies in a stratified fluid

R Plougonven, V Zeitlin

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Geostrophic adjustment of frontal anomalies in a rotating continuously stratified fluid is studied in the standard framework of strictly rectilinear fronts and jets. Lagrangian approach to this problem is developed allowing to analyze. in a conceptually and technically simple way. both major problems or the nonlinear adjustment: the existence or a smooth adjusted state for a given set or initial conditions and the attainability of the adjusted state during the adjustment process. Dynamical splitting into balanced (adjusted state) and unbalanced (inertia-gravity waves) motions becomes transparent in the Lagrangian approach. Conditions of existence or the balanced state in the unbalanced domain are established. It is shown that nonexistence or a smooth adjusted state in the vertically bounded domains is generic and a parallel with file classical scenario or deformation frontogenesis is developed. Small perturbations around smooth adjusted states are then studied with special emphasis on the wave-trapping inside the jet, front. Trapped modes with horizontal scales comparable to the width of the jet are explicitly constructed for a barotropic jet and their evolution is studied with the help or the WKB-approximation for weakly baroclinic jets. Modifications or the standard scenario of adjustment due to subinertial (quasi-) trapped modes and implications for data analysis are discussed.

Original languageEnglish
Pages (from-to)101-135
Number of pages35
JournalGeophysical and Astrophysical Fluid Dynamics
Volume99
DOIs
Publication statusPublished - Apr 2005

Keywords

  • frontogenesis
  • geostrophic adjustment
  • ROTATING SHALLOW-WATER
  • ZERO POTENTIAL VORTICITY
  • NONLINEAR-WAVE PHENOMENA
  • MONGE-AMPERE TYPE
  • PART 1
  • FRONTOGENESIS
  • ATMOSPHERE
  • EQUATIONS
  • STABILITY
  • MODELS

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