Uncovering the Edge of the Polar Vortex

Abstract

The polar vortices play a crucial role in the formation of the ozone hole and can cause severe weather anomalies. Their boundaries, known as the vortex `edges', are typically identified via methods that are either frame-dependent or return non-material structures, and hence are unsuitable for assessing material transport barriers. Using two-dimensional velocity data on isentropic surfaces in the northern hemisphere, we show that elliptic Lagrangian Coherent Structures (LCSs) identify the correct outermost material surface dividing the coherent vortex core from the surrounding incoherent surf zone. Despite the purely kinematic construction of LCSs, we find a remarkable contrast in temperature and ozone concentration across the identified vortex boundary. We also show that potential vorticity-based methods, despite their simplicity, misidentify the correct extent of the vortex edge. Finally, exploiting the shrinkage of the vortex at various isentropic levels, we observe a trend in the magnitude of vertical motion inside the vortex which is consistent with previous results.

References in corpus (4)

• On the Lagrangian Dynamics of Atmospheric Zonal Jets and the Permeability of the Stratospheric Polar Vortex
• Zonal Jets as Transport Barriers in Planetary Atmospheres
• Efficient Computation of Null-Geodesic with Applications to Coherent Vortex Detection
• Forecasting Long-Lived Lagrangian Vortices from their Objective Eulerian Footprints

Cited by in corpus (6)

• Finite-time Lyapunov exponents in the instantaneous limit and material transport
• Detecting Lagrangian coherent structures from sparse and noisy trajectory data
• Barriers to the Transport of Diffusive Scalars in Compressible Flows
• Internal wave boluses as coherent structures in a continuously stratified fluid
• Objective Momentum Barriers in Wall Turbulence
• Lagrangian study of the final warming in the southern stratosphere during 2002: Part I. The Vortex Splitting at Upper Levels