Variations of tropospheric ozone concentration over Syowa Station, Antarctica

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Abstract
Aircraft measurements of the tropospheric O3 concentration were made over Syowa Station (69°00′S, 39°35′E), Antarctica from May 1989 to January 1990, except during the polar night months of June and July. The O3 concentration increased with height for the whole period of the measurements. Lower tropospheric O3 showed a prominent seasonal variation with maximum concentration in winter and minimum concentration in summer, which is very close to the result of continuous O3 measurements initiated at Syowa Station in February 1988. In the upper troposphere, the concentration reached high values in winter, decreased gradually until late spring and then increased again. As a result, the height-dependent difference of the concentration was reduced from late autumn to early spring and enhanced in remaining seasons of the year. The seasonal variation of upper tropospheric O3 was similar to those of the lower stratospheric O3 concentration measured by ozonesondes and the total amount of O3 by a Dobson spectrophotometer over Syowa Station. Inspection of TOMS (Total Ozone Mapping Spectrometer) data also suggested that the temporal variations of the upper tropospheric O3 measured in this study are closely related to those of the lower stratospheric O3 over Syowa Station. Comparison of the results of surface O3 measurements in the southern hemisphere showed that the concentration increase going southward, and appearance of the minimum concentration of the seasonal variation is delayed by almost 1 month at the South Pole compared to Syowa Station and Cape Grim, Tasmania. Taking into account these results, it is suggested that the intrusion of stratospheric O3 into the troposphere occurs over Syowa Station throughout the year, and that air with low O3 concentrations is transported from subpolar or middle latitudes to the station through the lower troposphere from spring to early autumn, in addition to the photochemical destruction of O3 near the station. DOI: 10.1034/j.1600-0889.1992.t01-3-00004.x

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