Chemical ozone loss in the Arctic winter 1994/95 as determined by the Match technique

The chemically induced ozone loss inside the Arctic vortex during the winte r 1994/95 has been quantified by coordinated launches of over 1000 ozoneson des from 35 stations within the Match 94/95 campaign. Trajectory calculatio ns, which allow diabatic heating or cooling, were used to trigger the ballo on launches so that the ozone concentrations in a large number of air parce ls are each measured twice a few days apart. The difference in ozone concen tration is calculated for each pair and is interpreted as a change caused b y chemistry. The data analysis has been carried out far January to March be tween 370 K and 600 K potential temperature. Ozone loss along these traject ories occurred exclusively during sunlit periods, and the periods of ozone loss coincided with, but slightly lagged, periods where stratospheric tempe ratures were low enough for polar stratospheric clouds to exist. Two clearl y separated periods of ozone loss show up. Ozone loss rates first peaked in late January with a maximum value of 53 ppbv per day (1.6 % per day) at 47 5 K and faster losses higher up. Then, in mid-March ozone loss rates at 475 K reached 34 ppbv per day (1.3 % per day), faster losses were observed low er down and no ozone loss was found above 480 K during that period. The ozo ne loss in hypothetical air parcels with average diabatic descent rates has been integrated to give an accumulated loss through the winter. The most s evere depletion of 2.0 ppmv (60 %) took place in air that was at 515 K on 1 January and at 450 K an 20 March. Vertical integration over the levels fro m 370 K to 600 K gives a column lass rate, which reached a maximum value of 2.7 Dobson Units per day in mid-March. The accumulated column loss between 1 January and 31 March was found to be 127 DU (similar to 36 %).