Abstract:Continuous surface ozone measurements and regular ECC ozone sonde launches were used, in order to study the dynamical processes during the formation of tropospheric ozone depletion events at Neumayer Station (70°S; 08°W) in 1992 and 1993. Meteorological data, weather charts, ice charts as well as trajectory calculations have been considered for this analysis. Altogether eight events of surface ozone minima were recorded, four of them from June to August 1992 and another four in the period from August to September in 1993, respectively. The duration of these low ozone events was about 1-2 days. During this time ozone mixing ratios varied between 8 ppbv and 24 ppbv. Ozone sonde data showed that those ozone poor layers were restricted to the planetary boundary layer up to a subsidence inversion, indicating their upper limit. In general, those ozone poor air masses were exposed by sunlight during transport across the ice covered Southern Ocean. Beside these general features, typical cases could be identified which might be explained by the special dynamical conditions in the Antarctic coastal region. In September 1993 two events with an elevated ozone poor layer were observed due to the influence of continental winds. In June 1992 an ozone minimum was also detected at Neumayer Station during polar night conditions. In this case the ozone depleted air mass was probably transported from sunlit regions located northward from Neumayer Station where the exposure by sunlight occurred.