Speaker
Description
Energetic particle precipitation (EPP) provides an important pathway for space weather to influence the middle and lower atmosphere, yet its role in atmospheric variability and predictability remains uncertain. While EPP-driven production of NOx and subsequent ozone depletion can affect stratospheric dynamics and surface climate, observational constraints are limited: reanalysis products rely on indirect proxies, and separating EPP signals from internal variability is challenging. This motivates a modeling-based approach to isolate mechanisms and assess their robustness.
Here, we investigate EPP impacts on atmospheric chemistry, dynamics, and surface climate using long-term time-slice simulations with the SOCOLv4.0 chemistry–climate model. Simulations are performed under pre-industrial conditions, with EPP forcings based on the strong 2003 "Halloween storms" and weak 2008 events. Consistent with established understanding, EPP enhances polar NOx, depletes ozone, and modifies stratospheric and tropospheric circulation through coupled radiative–dynamical feedbacks. However, the sign of the polar vortex and surface response depends on both hemisphere and the timing of strong EPP events.
In addition, we identify a delayed pathway: mid-latitude ozone depletion caused by post-winter transport of EPP-produced NOx, which can precondition the stratosphere and modulate the following winter’s polar vortex, at times opposing the canonical EPP response. This points to a seasonal memory effect and raises the question of how robust such mechanisms are under realistic conditions, particularly during multiyear periods of enhanced EPP associated with solar cycle maxima, and whether they contribute meaningfully to climate predictability.