Publication details
Journal: Polar Science, vol. 50, 101434, December 1st 2026
Doi: doi.org/10.1016/j.polar.2026.101434
Arkiv: hdl.handle.net/11250/5577754
Archive: nva.sikt.no/registration/01a0e700f459-1a5ad812-af2b-441b-b4d4-17c6c8093894
Summary:
Exceptionally low total ozone column (TOC) values were observed over Europe in February 2023, affecting both Arctic and mid-latitude regions. This study investigates the evolution and underlying mechanisms of this low-ozone episode by integrating ground-based observations, satellite measurements, and atmospheric reanalysis data. Daily TOC data from Andøya, Oslo/Kjeller, and Hradec Králové are complemented by multi-sensor reanalysis products and vertically resolved measurements from the Microwave Limb Sounder (MLS). The lowest TOC values occurred on 14 February 2023, when all three stations recorded anomalies below the 2σ climatological threshold. This period coincided with a cold stratospheric polar vortex, which promoted the formation of polar stratospheric clouds and subsequent chemical ozone loss. MLS observations reveal pronounced decreases in HNO3 and HCl, accompanied by enhanced ClO concentrations, indicating active halogen-driven ozone loss. The strongest chemical ozone depletion was observed over Scandinavia and later extended toward Central Europe. In addition to chemical processes, dynamical factors significantly contributed to the observed TOC reduction. Elevated tropopause heights and the transport of ozone-poor air from lower latitudes further reduced TOC, particularly over Central Europe. The results demonstrate that the February 2023 low-ozone event arose from the combined effects of chemical ozone loss within cold polar vortex air and large-scale dynamical processes, emphasizing the importance of integrated chemical–dynamical analyses for understanding extreme Arctic ozone events.