Geodesic vortex detection on curved surfaces: Analyzing the 2002 austral stratospheric polar vortex warming event

Area of Science:

• Nonlinear dynamical systems
• Atmospheric science
• Fluid dynamics

Background:

• Geodesic vortex detection objectively identifies transient vortices in nonlinear dynamical systems.
• The technique was initially developed for 2D Cartesian flows but needed adaptation for manifold geometries.
• Understanding stratospheric vortex dynamics is crucial for climate and ozone layer research.

Purpose of the Study:

• Extend geodesic vortex detection to 2D Riemannian manifolds.
• Adapt vortex birth-and-death framing for 3D stratospheric flows.
• Analyze the kinematic life cycle of the austral polar vortex during the 2002 sudden warming event.

Main Methods:

• Formulated geodesic vortex detection for 2D Riemannian manifolds, including objectivity.
• Adapted a birth-and-death vortex framing algorithm for stratospheric applications.
• Applied the extended technique to isentropic wind reanalysis data for the austral polar vortex.

Main Results:

• Successfully tracked the austral stratospheric polar vortex's life cycle, including its birth, splitting, and death.
• Documented the vortex splitting during the exceptional 2002 sudden warming event.
• Provided kinematic insights into the dynamics of ozone depletion within the vortex.

Conclusions:

• The extended geodesic vortex detection is effective for analyzing vortex dynamics on manifolds, like the stratosphere.
• The study offers a detailed kinematic description of the polar vortex splitting event.
• New insights into vortex-related ozone depletion mechanisms were uncovered.