摘要： There are only four lidar stations in the world, which have almost continuously performed observations of the stratospheric aerosol layer (SAL) state for over the last 30 years. The longest time series of the SAL lidar measurements have been accumulated at the Mauna Loa Observatory (Hawaii) since 1973, the NASA Langley Research Center (Hampton, Virginia) since 1974, and Garmisch-Partenkirchen (Germany) since 1976. The fourth lidar station we present started to perform routine observations of the SAL parameters in Tomsk (56.48° N, 85.05° E, Western Siberia, Russia) in 1986. In this paper, we mainly focus on and discuss the stratospheric background period from 2000 to 2005 and the causes of the SAL perturbations over Tomsk in the 2006–2015 period. During the last decade, volcanic aerosol plumes from tropical Mt. Manam, Soufriere Hills, Rabaul, Merapi, Nabro, and Kelut, and extratropical (northern) Mt. Okmok, Kasatochi, Redoubt, Sarychev Peak, Eyjafjallaj?kull, and Grimsv?tn were detected in the stratosphere over Tomsk. When it was possible, we used the NOAA HYSPLIT trajectory model to assign aerosol layers observed over Tomsk to the corresponding volcanic eruptions. The trajectory analysis highlighted some surprising results. For example, in cases of the Okmok, Kasatochi, and Eyjafjallaj?kull eruptions, the HYSPLIT air-mass backward trajectories, started from altitudes of aerosol layers detected over Tomsk with a lidar, passed over these volcanoes on their eruption days at altitudes higher than the maximum plume altitudes given by the Smithsonian Institution Global Volcanism Program. An explanation of these facts is suggested. The role of both tropical and northern volcanoes eruptions in volcanogenic aerosol loading of the mid-latitude stratosphere is also discussed. In addition to volcanoes, we considered other possible causes of the SAL perturbations over Tomsk, i.e. the polar stratospheric cloud (PSC) events and smoke plumes from strong forest fires. At least two PSC events were detected in 1995 and 2007. We also make an assumption that both the Kelut volcano plume (Indonesia, February 2014) and smoke plumes from massive forest fires occurred in Canada (137 fires in the Northwest Territories, July 2014) and the USA (the Happy Camp Complex fire in California, August–October 2014), with equal probability, could be the cause of the SAL perturbations over Tomsk during the first quarter of 2015.