TY CONF TI ASSESSMENT OF SEASONAL TRENDS OF BACKGROUND STRATOSPHERIC AEROSOL IN WESTERN SIBERIA BASED ON LIDAR SOUNDING DATA KW stratosphere KW background aerosol KW lidar monitoring KW statistical analysis KW seasonal trends KW Western Siberia JO International Symposium Atmospheric and Ocean Optics. Atmospheric Physics AU Marichev, V.N. AU Elizarov, A.I. PY 2026 PB V.E. Zuev Institute of Atmospheric Optics, Siberian Branch of the Russian Academy of Sciences