Studies and predictions of solar influences on polar vortex and winter climate
Thesis event information
Date and time of the thesis defence
Place of the thesis defence
Auditorium L5, Linnanmaa campus
Topic of the dissertation
Studies and predictions of solar influences on polar vortex and winter climate
Doctoral candidate
Master of Science Mikhail Vokhmianin
Faculty and unit
University of Oulu Graduate School, Faculty of Science, Space Physics and Astronomy research unit
Subject of study
Atmospheric physics
Opponent
Associate Professor Blanca Ayarzagüena, Complutense University of Madrid
Custos
Professor Timo Asikainen, University of Oulu
How solar activity influences the winter atmosphere and surface weather
The outer layer of the Sun is very active, which is often described by an approximately 11-year cycle measured by the number of sunspots visible on its surface. These changes affect not only solar radiation, but also the number and energy of particles streaming from the Sun into space. On Earth, enhanced solar activity is often seen as more frequent auroras and geomagnetic storms, both resulting from increased fluxes of energetic particles.
When energetic particles from the Sun enter the polar upper atmosphere, they can trigger chemical changes that reduce ozone in the mesosphere and wintertime stratosphere. At the same time, changes in solar ultraviolet radiation influence ozone in the tropics. Ozone is important not only because it protects life from harmful ultraviolet radiation, but also because it helps regulate temperatures in the middle atmosphere.
During winter, strong temperature differences between low and high latitudes create circumpolar winds known as the polar vortex. The strength of this vortex is closely connected to atmospheric temperature and can influence tropospheric weather near the ground, especially in high-latitude regions such as Northern Europe.
This thesis shows that enhanced fluxes of solar energetic particles are generally linked to a stronger polar vortex. This connection is particularly clear when studying sudden stratospheric warming events, during which the polar vortex rapidly weakens. These events can lead to large changes in the polar stratosphere that may extend downward and affect surface weather. The thesis also shows that geomagnetic activity is connected to wintertime temperature variations in Finland and, therefore, to electricity consumption. Such solar-related effects are strongest when the equatorial stratosphere is in a favorable state. Because solar activity and the stratosphere are generally more predictable than highly turbulent surface weather, understanding these links may help improve long-term winter weather forecasts.
When energetic particles from the Sun enter the polar upper atmosphere, they can trigger chemical changes that reduce ozone in the mesosphere and wintertime stratosphere. At the same time, changes in solar ultraviolet radiation influence ozone in the tropics. Ozone is important not only because it protects life from harmful ultraviolet radiation, but also because it helps regulate temperatures in the middle atmosphere.
During winter, strong temperature differences between low and high latitudes create circumpolar winds known as the polar vortex. The strength of this vortex is closely connected to atmospheric temperature and can influence tropospheric weather near the ground, especially in high-latitude regions such as Northern Europe.
This thesis shows that enhanced fluxes of solar energetic particles are generally linked to a stronger polar vortex. This connection is particularly clear when studying sudden stratospheric warming events, during which the polar vortex rapidly weakens. These events can lead to large changes in the polar stratosphere that may extend downward and affect surface weather. The thesis also shows that geomagnetic activity is connected to wintertime temperature variations in Finland and, therefore, to electricity consumption. Such solar-related effects are strongest when the equatorial stratosphere is in a favorable state. Because solar activity and the stratosphere are generally more predictable than highly turbulent surface weather, understanding these links may help improve long-term winter weather forecasts.
Created 28.4.2026 | Updated 30.4.2026