Maintenance of high HCl/Cl(y) and NO(x)/NO(y) in the Antarctic vortex - A chemical signature of confinement during spring

• Published in: Journal of Geophysical Research Vol. 104; no. D21; p. 26
• Main Authors: Michelsen, H A, Webster, C R, Manney, G L, Scott, D C, Margitan, J J, May, R D, Irion, F W, Gunson, M R, Russell III, J M, Spivakovsky, C M
• Format: Journal Article
• Language: English
• Published: United States 20-11-1999
• Subjects: ANTARCTIC REGIONS; ATMOSPHERIC CHEMISTRY; CHLORINE; ENVIRONMENTAL SCIENCES; EXPERIMENTAL DATA; GEOPHYSICS; NITROGEN COMPOUNDS; OZONE; PHOTOCHEMISTRY; RADICALS
• ISSN: 0148-0227; 2156-2202
• DOI: 10.1029/1999JD900473

Observations made in the 1994 Antarctic vortex show that Cl(y) recovered completely into HCl following conversion of Cl(y) reservoir species to active radicals, and NO(x) constituted a 4-5 times higher fraction of NO(y) inside the vortex than outside. Measurements made in October and November demonstrate that this unusual partitioning of Cl(y) and NO(y) was maintained for at least four weeks in the springtime vortex. In response to severe ozone loss, abundances of HCl and NO(x) remained high despite temperatures low enough to reactivate Cl(y) and convert NO(x) to HNO3 via heterogeneous processes. Thus, under severely ozone depleted conditions, high HCl and NO(x) abundances in the vortex are maintained until the vortex breaks up or an influx of ozone-rich extravortex air is entrained into the vortex. These observations suggest that the flux of extravortex air entering the core of the lower stratospheric vortex was small or negligible above about 400 K during late spring, despite weakening of the vortex during this time period. Results of a photochemical model constrained by the measurements suggest that extravortex air entrained into the vortex during October and early November made up less than 5 percent of the vortex core air at 409 K. The model results also show that heterogeneous chemistry has little effect on the Cl(y) and NO(y) partitioning once high abundances of HCl have been attained under ozone depleted conditions, even when aerosol loading is high. (Author)