Variability and Trends in Ozone and Ozone-Related Stratospheric Trace Gases over St. Petersburg (Russia)

Anomalous ozone loss in the Northern Hemisphere during winter–spring periods has been increasingly observed in recent decades. Regular monitoring of stratospheric gases involved in ozone-depleting processes is essential for predicting the appearance of ozone mini-holes and the growth in UV surface irradiance. The St. Petersburg State University site located on the border of mid- and high latitudes is equipped with the Bruker IFS 125HR spectrometer for trace gas measurements and the UV and VIS Ocean Optics HR4000 spectrometers for total ozone column (TOC) measurements. The harmonization of TOC series from three instruments made it possible to analyze TOC variability during rapid changes in air masses. A decrease in ozone in the 8–18 km (−0.41 ± 0.33% yr−1) and 18–25 km (−0.17 ± 0.15% yr−1) layers, as well as in stratospheric HNO3 (−0.31 ± 0.18% yr−1), is observed for the 2009–2026 period, along with an increase in HF (+0.41 ± 0.20% yr−1) mainly due to changes in atmospheric dynamics over the past decade. An observed decrease in CCl3F (−0.43 ± 0.06% yr−1), CCl2F2 (−0.71 ± 0.04% yr−1), ClONO2 (−1.14 ± 0.82% yr−1), and HCl (−0.31 ± 0.16% yr−1) indicates a decrease in the chlorine-containing gases in the atmosphere. A comparison of the EMAC and SOCOLv3 simulations with observations for the common 2009–2019 period showed that ozone variability, including trends, seasonal variations, and rapid winter–spring changes, is described by the models within the measurement uncertainty limits, whereas for HCl, ClONO2, and HNO3, the quantitative discrepancy between the simulations and measurements exceeds the corresponding measurement uncertainty.