Is ozone destroyed during the Antarctic winter in the presence of polar stratospheric clouds?

Abstract

SINCE the discovery of the springtime Antarctic ozone depletion^1–2 a great deal of attention has been given to processes related to aerosol formation and heterogeneous chemistry at low tem-peratures. Polar stratospheric cloud (PSCs),³ are frequent features of the southern winter atmosphere, and may provide a site for heterogeneous reactions that lead to ozone destruction^4,5. Models have been proposed^6–8 for the formation of PSCs based on the condensation of HNO₃ (see ref. 9 for a review). An optical radar (lidar) has been operated at Amundsen Scott (South Pole), Antarctica, since the austral summer 1987–88. Observations made during the 1988 polar night show the presence of PSCs. Here we report ozonesonde measurements made quasi-simultaneously at the South Pole which indicate sharp minima of the ozone concentration in the vicinity of the PSCs. Although definitive information is unavailable for unambiguous interpretation of the results, the data may be viewed as evidence either for the role of dynamics in transporting air of different composition in conditions of substantial stability, or for processes leading to ozone destruction during the polar winter; the latter may include heterogeneous chemical reactions taking place in the absence of photolysis.