CHEMICAL LOSS OF OZONE IN THE ARCTIC POLAR VORTEX IN THE WINTER OF 1991-1992

In situ measurements of chlorine monoxide, bromine monoxide, and ozone are extrapolated globally, with the use of meteorological tracers, to infer the loss rates for ozone in the Arctic lower stratosphere durin g the Airborne Arctic Stratospheric Expedition II (AASE II) in the win ter of 1991-1992. The analysis indicates removal of 15 to 20 percent o f ambient ozone because of elevated concentrations of chlorine monoxid e and bromine monoxide. Observations during AASE II define rates of re moval of chlorine monoxide attributable to reaction with nitrogen diox ide (produced by photolysis of nitric acid) and to production of hydro chloric acid. Ozone loss ceased in March as concentrations of chlorine monoxide declined. Ozone losses could approach 50 percent if regenera tion of nitrogen dioxide were inhibited by irreversible removal of nit rogen oxides (denitrification), as presently observed in the Antarctic , or without denitrification if inorganic chlorine concentrations were to double.