Tropospheric blocking associated with late-autumn minor sudden stratospheric warmings over the Arctic

The stratospheric circulation during the winter half-year at high latitudes is characterised by strong west-to-east winds, also known as the stratospheric polar vortex. These polar vortices, especially in the Northern Hemisphere, are usually disrupted by planetary waves, with extreme cases of these disruptions being sudden stratospheric warmings (SSWs). They most commonly occur in the second half of winter and in early spring, but in rare cases, they may also occur in November or December. This study examines three minor SSW events occurring in November 2000, 2009, and 2025 to identify the tropospheric conditions that influenced their development. These minor SSWs were identified using ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF), based on the zonal mean wind at 60° N at 10 hPa. The first event occurred on 29 November 2000, the second on 17 November 2009, and the third on 28 November 2025. In all three cases, the most pronounced heat flux from the troposphere to the stratosphere was centred over central Siberia, followed by a secondary maximum observed over Alaska. It was shown that the position of blocking anticyclones determines their interaction with tropospheric planetary waves, thereby indirectly modulating the upward propagation of wave activity into the stratosphere. Enhanced wave activity led not only to higher stratospheric temperatures but also to increased total ozone column, with values exceeding the 2σ threshold over the 60–90° N region. Since November, SSWs have remained relatively understudied; this work provides new insights into these phenomena and establishes a framework for future research.