Quasi-biennial oscillation in variations of vertical distribution of midlatitude stratospheric ozone and aerosol

Based on analysis of data of lidar, spectrophotometric, and satellite measurements of integrated content of stratospheric ozone and aerosol for period 1986-2002 for observation site in Tomsk (56.48 degrees N, 85.05 degrees E), earlier we showed the presence of quasibiennial oscillation (QBO) of variations of their integrated content. The report analyzes data of lidar measurements of ozone and aerosol vertical distributions for background stratospheric state under conditions of extended volcanically quiet period 1996-2005. For analysis, we averaged profiles corresponding to easterly and westerly QBO phases, which were determined from monthly mean zonal wind components in the equatorial stratosphere. Larger aerosol content is observed in westerly QBO phases, and larger ozone content in easterly phases, in correspondence with views on general stratospheric circulation. Differences are most marked in the lower stratosphere, up to heights about 22 km. In the lower stratosphere, we also observe insignificantly larger aerosol content in winter-spring than summer-fall period. The presence of seasonality and quasibiennial oscillation, with increase of aerosol content at midlatitudes in periods of intensification of winter-spring meridional transport from tropical belt to midlatitudes and in westerly QBO phases, is an evidence in favor of hypothesis on the presence of tropical reservoir of background stratospheric aerosol.