Speaker
Description
Space climate affects not only the magnetosphere and ionosphere, but also the middle atmosphere, including the mesosphere (50–80 km) and stratosphere (15–50 km). Variations in solar radiation and precipitating energetic particles (EPP) influence atmospheric composition, particularly ozone, which plays a central role in the atmospheric radiative balance through its absorption of shortwave and longwave radiation and its emission in the longwave range.
During polar winter, in the absence of solar radiation, the lifetime of NOx compounds produced by EPP increases substantially. Under conditions of enhanced EPP activity, wintertime circulation transports larger amounts of NOx downward into the lower mesosphere and upper stratosphere, where these compounds catalytically destroy ozone. The resulting ozone changes alter the local radiative balance and thereby affect temperature and eventually strengthen the polar vortex. The associated anomalies can then propagate downward and occasionally influence the troposphere.
This downward coupling is particularly relevant in winter, when stratosphere–troposphere interactions are strongest, especially in connection with sudden stratospheric warming (SSW) events, which are known to affect weather over large parts of the Northern Hemisphere. The occurrence of these events was found to be suppressed during periods of high EPP. Because the stratosphere is generally less chaotic than the troposphere, improved understanding of space-climate forcing, and especially better predictability of solar forcing, may offer a pathway to improved subseasonal predictability of winter weather in the troposphere. This highlights the societal relevance of space climate. For instance, we have recently shown that Finland’s electricity consumption and wind power generation correlate with geomagnetic activity during winters with favorable equatorial stratospheric winds.