Chemistry of the reactive nitrogen in the Antarctic stratosphere

• Main Authors: Yutaka Kondo, Makoto Koike
• Format: Article in Journal/Newspaper
• Language: English
• Published: National Institute of Polar Research 1997
• Subjects: geo; Antarctic; Austral; Syowa Station; The Antarctic; Antarc*; Antarctica
• Online Access: https://doi.org/10.15094/00008975; https://doaj.org/article/cbdffa0e6b5448288c2eafcffa563fe3

Low levels of reactive nitrogen species are essential for large stratospheric ozone (O_3) depletion over the Antarctic continent in the austral spring (Antarctic ozone hole), because ClO is sequestered by a reaction with NO_2 to form a quasi-stable molecule ClONO_2. The column amounts of NO_2 have been measured using a visible spectrometer at Syowa Station, Antarctica (69°S) since March 1990. The NO_2 column exhibits a large seasonal variation with a maximum in summer and a minimum in winter. The recovery of NO_2 in spring is 2-3 times slower than the fall decay. The low NO_2 level in mid-winter to early spring is considered to be due to a conversion into HNO_3 on PSCs and due to the denitrification by gravitational sedimentation of PSC particles. Results from a chemical box model agreed well with this slow rate of NO_2 increase in spring when heterogeneous chemistry on PSCs was included. The reduction of NO_2 by 30% was found after the breakup of the austral polar vortex in 1992. This is probably due to the transport of air from lower latitudes, where NO_2 is reduced by heterogeneous conversion into HNO_3 on the surface of sulfate aerosols increased by the Pinatubo volcanic eruption.