The 2025 Canadian wildfires: a new formation of smoke charged vortex

With global warming, Canada is increasingly affected by extreme weather events, mainly wildfires. With more than 8.3 million hectares burned over the country, the 2025 Canadian fire season is the second-worst on record after 2023. The associated emissions injected an exceptional aerosol load in the Northern Hemisphere upper troposphere – lower stratosphere (UTLS). Part of the emitted aerosols reached the lower stratosphere and, over Europe, organized into a new “smoke-charged vortex” (SCV). SCVs – anticyclonic structures that confine polluted air into long-lived “smoke bubbles” – have already been documented and studied after the “Pacific Northwest Event” (PNE) in Canada in 2017 and the “Australian New Year” event (ANY) in Australia in 2019-2020, making the 2025 event the third such case identified to date. Once formed, their anticyclonic circulation tends to limit dilution and mixing with the ambient air, maintaining high black-carbon-rich aerosol concentrations and chemical species emitted from biomass burning – for weeks to months within these vortices. These include carbon monoxide (CO), water vapor (H₂O), inorganic compounds such as nitrogen-(NOx) and chlorine-(ClOx) containing species, and a range of organic compounds such as non-methane hydrocarbons (NMHCs) and oxygenated volatile organic compounds (OVOCs), all of which play key roles in atmospheric chemistry.

In this study, we track the SCV over Europe using vorticity anomaly, analyse its aerosol burden using balloon-borne and satellite observations and characterize its chemical composition. Together, these results provide a comprehensive overview on the SCV characteristics and place the 2025 event in context with the previously documented PNE and ANY cases.