Disturbance of the Stratosphere over Tomsk during Winter 2017/2018 Using Lidar and Aura MLS/OMI Observations

Lidar observations at Siberian Lidar Station (SLS) of the Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, in Tomsk (56.5° N; 85.0° E) showed the presence of stratospheric aerosol layers, descent of air masses, and deficit of ozone over the city during winter 2017–2018. Aura OMI/MLS data indicated that the total ozone (TO) content and NO2 content in the stratosphere over northern Eurasia, as well as the temperature in the stratosphere, were significantly lower than normal in December 2017–January 2018. Analysis of back trajectories and integrated (over profile) TO showed that the dynamic disturbance of the Arctic stratosphere in December 2017 led to the extrusion of cold air masses with excessive reactive chlorine content (in view of NO2 deficit) beyond the Arctic circle and their intrusion into the stratosphere of Tomsk. Seemingly, they were exposed to solar radiation in the stratosphere over Tomsk and, staying spatially isolated, became chemically disturbed. This state is similar to the state of the springtime Arctic stratosphere, where ozone is intensely destroyed until the final warming.