Far-flung influences on midlatitude weather and climate: The stratospheric pathway

The variability of the Northern Hemisphere stratospheric polar vortex can significantly influence, and enhance the predictability of, midlatitude winter weather on timescales of weeks to months – including the likelihood of weather extremes and associated impacts. This thesis first explores the response of the polar vortex to projected Arctic climate change, in terms of both the mean state and variability, before focusing on the impact of sudden stratospheric warmings (SSWs) on European energy demand. The “stratospheric pathway” proposed to link Arctic sea-ice loss to changes in midlatitude weather and climate is not well understood; studies do not so far find a robust stratospheric response to sea-ice loss in either strength or sign. A series of idealised model simulations is first used to show that the stratospheric response is sensitive to characteristics of the near-surface Arctic warming and mean state of the vortex. Then, a novel analysis of the stratospheric response with thirteen complex atmospheric models is conducted, looking beyond the typical time- and zonal-mean diagnostics. Though this analysis confirms the lack of robust response, the possible role of ensemble size, resolution, and stratospheric basic state to explain the range of simulated responses is explored. In both, the stratospheric response is also found to play a role in the magnitude of the tropospheric jet response. Finally, the contribution of SSWs to extreme European energy events is inves- tigated. Reanalysis-derived variables indicate that extreme high energy demand across northern and central Europe is historically more likely and severe following such events. Stratospheric nudging experiments in seven seasonal forecast models then enable specific attribution of energy extremes to the occurrence of the 2018 SSW. The results indicate a notable dependence on the lead time and nudging methodology in the relative risk of extremes.<p></p>

Author dc:creator

• Regan Mudhar (21061334)

• Atmospheric dynamics
• Stratosphere
• Polar climate
• Climate change
• Energy sector

Statement dc:rights

• All rights reserved
• Open Access after 2027-02-02

Identifier

10779/exe.31211725.v1

OAI identifier oai:identifier

oai:figshare.com:article/31211725