Speaker
Description
In wintertime, the stratospheric polar vortex strongly influences European weather, affecting temperature, wind speed, and cloudiness. A strong polar vortex is typically associated with milder, windier, and cloudier conditions in northern Europe, while colder, calmer, and clearer weather prevails in southern Europe. Cloudiness directly controls the amount of solar radiation reaching the surface and therefore modulates solar power production.
One important factor influencing the polar vortex, and consequently surface weather, is energetic electron precipitation (EEP), for which the geomagnetic aa index can be used as a proxy. Enhanced EEP increases ozone loss in the upper atmosphere, leading to stratospheric cooling and a strengthened polar vortex. However, the influence of EEP on the polar vortex is strongest during the easterly phase of the quasi-biennial oscillation (QBO), which enhances planetary wave activity and meridional circulation transporting ozone toward polar regions. While the impacts of EEP on surface temperature and wind speed via the polar vortex have been investigated, its effects on cloud cover and surface incoming solar radiation remain largely unexplored.
In wintertime, countries in southern and central Europe receive sufficient solar radiation to produce a significant fraction of their electricity demand through solar power. In this study, we examine how winter cloud cover, surface incoming solar radiation, and solar power production respond to the strength of the polar vortex and geomagnetic activity across Europe. We find that stronger geomagnetic activity and stronger polar vortex in the easterly QBO phase are associated with reduced cloudiness and higher surface solar radiation in southern Europe, which enhances solar power production. For example, in Spain, the NAM index, which reflects the strength of the polar vortex, shows a correlation of 0.77 with solar power, while geomagnetic activity exhibits a correlation of 0.67. In both cases, the correlations are statistically highly significant.