Study of surface ozone concentrations in the air of an industrial Russian city

The aim of this work was to analyse seasonal changes of surface ozone concentrations (SO), to study cases of exceeding maximum permissible concentrations (MPC), extreme ozone episodes (EOEs) and nocturnal ozone enhancement (NOE) in order to propose mechanisms for the phenomena described and effective strategies for achieving established standards. In the course of the work, the concentrations of SO and its predicates were studied at the state air monitoring station in the city of Chelyabinsk during 2019–2021. According to the research results, it was revealed that the SO concentration in the Chelyabinsk urban area begins to increase in March and remains high during the summer. The SO concentration consists of several components: (1) that transported from the lower stratosphere and the upper layers of the troposphere as a result of stratospheric invasions (SI), which increase in summer; (2) that formed photochemically with a maximum in June: while the HCHO/NOx ratio calculated on the basis of ground‐based monitoring data cannot be used as a reliable indicator of SO formation; and (3) that incoming with low‐level jets (LLJs), the frequency of which increases during the night in spring and summer, as evidenced by the high frequency of NOE.