Isentropic Transport within the Antarctic Polar-Night Vortex: Rossby Wave Breaking Evidence and Lagrangian Structures

• Published in: Journal of the atmospheric sciences 2013-09, Vol.70 (9), p.2982-3001
• Main Authors: DE LA CAMARA, Alvaro, MECHOSO, Carlos R, MANCHO, Ana M, SERRANO, Encarna, IDE, Kayo
• Format: Article
• Language: English
• Subjects: Air parcels; Antarctic vortex; Antarctica; Balloons; Configurations; Domains; Dynamical systems; Earth, ocean, space; Exact sciences and technology; External geophysics; Fields; Filamentation; Filaments; Fluid flow; Hyperbolic trajectories; Lower stratosphere; Mathematical analysis; Meteorological balloons; Meteorology; Night; Ozone; Physics of the high neutral atmosphere; Planetary waves; Polar vortex; Potential vorticity; Propagation; Rossby wave breaking; Rossby waves; Stratosphere; Stratospheric polar vortexes; Stratospheric vortices; System theory; Tracers; Transport; Velocity; Vortices; Vorticity; Wave breaking
• ISSN: 0022-4928; 1520-0469
• DOI: 10.1175/jas-d-12-0274.1

The trajectories in the lower stratosphere of isopycnic balloons released from Antarctica by Vorcore and Concordiasi field campaigns during the southern springs of 2005 and 2010 showed events of latitudinal transport inside the stratospheric polar vortex, both away from and toward the poleward flank of the polar-night jet. The present paper applies trajectory-based diagnostic techniques to examine mechanisms at work during such events. Reverse domain-filling calculations of potential vorticity (PV) fields from the ECMWF Interim Re-Analysis (ERA-Interim) dataset during the events show irreversible filamentation of the PV fields in the inner side of the polar-night jet, which is a signature of planetary (Rossby) wave breaking. Balloon motions during the events are fairly consistent with the PV filaments. Events of both large (~15 degree of arc length) and small (~5 degree of arc length) balloon displacements from the vortex edge are associated, respectively, with deep and shallow penetration into the core of the elongated PV contours. Additionally, the Lagrangian descriptor M is applied to study the configuration of Lagrangian structures during the events. Breaking Rossby waves inside the vortex lead to the presence of hyperbolic points. The geometric configuration of the invariant manifolds associated with the hyperbolic trajectories helps to understand the apparent chaotic behavior of balloons' motions and to identify and analyze balloon transport events not captured by reverse domain-filling calculations. The Antarctic polar vortex edge is an effective barrier to air parcel crossings. Rossby wave breaking inside the vortex, however, can contribute to tracer mixing inside the vortex and to occasional air crossings of the edge.