Chlorine activation and ozone depletion in the Arctic vortex: Observations by the halogen occultation experiment on the upper atmosphere research satellite

Abstract

Chlorine-catalyzed ozone destruction is clearly observed during austral spring in the Antarctic lower stratosphere. While high concentrations of ozone-destroying ClO radicals have likewise been measured during winter in the Arctic stratosphere, the chemical ozone depletion there is more difficult to quantify. Here we present observations of the Halogen Occultation Experiment on the Upper Atmosphere Research Satellite in the vortex region of the Arctic lower stratosphere during the winter and spring months of 1991/1992, 1992/1993, 1993/1994, and 1994/1995. All February measurements indicate an almost complete conversion of the otherwise main chlorine reservoir species HCl to chemically more reactive forms. Using CH4 as a chemically conserved tracer, we show that significant chemical ozone loss occurred in the Arctic vortex region during all four winters. The deficit in column ozone was about 60 and 50 Dobson units (DU) in the winters 1991/1992 and 1993/1994, respectively. During the two winters of 1992/1993 and 1994/1995 a severe chemical loss in lower-stratospheric ozone took place, with local reductions of the mixing ratios by over 50% and a loss in the column ozone of the order of 100 DU. Copyright 1996 by the American Geophysical Union.