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<p>The study of mesoscale eddies is generally categorized in Eulerian or Lagrangian frameworks. We employed the eddy identification techniques in both frameworks in the South China Sea (SCS), examining the differential characteristics of mesoscale eddies ascertained through each approach, and attempting to identify factors influencing eddy lifetime. The findings suggest that eddies identified via the sea surface height (SSH) method in the Eulerian framework typically have larger spatial extents compared to those identified using the Lagrangian Average Vorticity Deviation (LAVD) method. The latter is characterized by a greater number of vortices with smaller average values of characteristic parameters. SSH eddies exhibited more remarked seasonal variations than LAVD vortices, and the seasonal variations of their respective cyclonic and anticyclonic eddies showed opposite trends. Analysis in both frameworks indicates that eddy lifetime is positively correlated with various eddy characteristic parameters, including radius, vorticity, kinetic energy, amplitude, EKE/MKE (ratio of boundary to spatial mean kinetic energy), and <i>U</i>/<i>c</i> (max rotation speed to mean propagation speed ratio). A subsequent comparison between SSH eddies with LAVD cores (SSH eddy with LAVD vortex inside) and those without reveals a greater likelihood of extended lifetime in the former. Compared to the characteristic parameters of eddies, the presence of LAVD cores emerges as a critical factor in determining the lifetime of SSH eddies.</p>

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Comparative analysis of mesoscale eddies based on Eulerian and Lagrangian frameworks

  • 期刊论文

  • 发表日期：

    2025年8月26日

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  • Zekai Chen,
  • Yifan Liu,
  • Qiong Xia

摘要

The study of mesoscale eddies is generally categorized in Eulerian or Lagrangian frameworks. We employed the eddy identification techniques in both frameworks in the South China Sea (SCS), examining the differential characteristics of mesoscale eddies ascertained through each approach, and attempting to identify factors influencing eddy lifetime. The findings suggest that eddies identified via the sea surface height (SSH) method in the Eulerian framework typically have larger spatial extents compared to those identified using the Lagrangian Average Vorticity Deviation (LAVD) method. The latter is characterized by a greater number of vortices with smaller average values of characteristic parameters. SSH eddies exhibited more remarked seasonal variations than LAVD vortices, and the seasonal variations of their respective cyclonic and anticyclonic eddies showed opposite trends. Analysis in both frameworks indicates that eddy lifetime is positively correlated with various eddy characteristic parameters, including radius, vorticity, kinetic energy, amplitude, EKE/MKE (ratio of boundary to spatial mean kinetic energy), and U/c (max rotation speed to mean propagation speed ratio). A subsequent comparison between SSH eddies with LAVD cores (SSH eddy with LAVD vortex inside) and those without reveals a greater likelihood of extended lifetime in the former. Compared to the characteristic parameters of eddies, the presence of LAVD cores emerges as a critical factor in determining the lifetime of SSH eddies.