Summary of the Discussion on Large-Scale Atmospheric Extreme Weather Events in Stockholm

Extreme, high-impact weather events have serious social and economic consequences, and have garnered widespread scientific and media attention. Understanding their drivers and improving their prediction is therefore a topic of crucial societal and economic value, where the interests of academia, policy makers and private stakeholders converge. The workshop, organized by G. Messori and R. Caballero in Stockholm, gathered scientists and industry experts from six countries focusing on the mechanistic understanding and prediction of societally relevant extreme weather events in the mid and high latitudes. These included: warm and cold temperature extremes, extra-tropical cyclones and precipitation extremes. The aim was to bring together speakers from a diverse range of backgrounds spanning the atmospheric sciences, the private sector, applied mathematics and statistical mechanics to present their latest findings and trace an avenue for the future development of this very active research field.
The workshop provided compelling evidence that the study of recurrent large-scale atmospheric flows affords powerful insights into the mechanisms and predictability of regional weather extremes and revealed promising synergies between this paradigm and novel analysis tools drawn from dynamical systems theory and statistical mechanics. These tools provide a means of obtaining large samples of extreme events and the associated large-scale atmospheric patterns, something which is impossible to recover from the observational dataset and very costly to generate from long climate model simulations. They also provide a framework to diagnose changes in the atmospheric dynamics – and the associated extremes – in both past and future climates by using mathematically robust atmospheric  indicators whose definition is independent of the variable, geographical domain or season chosen. The local properties of atmospheric attractors, for example, are entirely general properties of a chaotic system.
More information and the full paper about the workshop here on the Bulletin of the American Meteorological Society: http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-17-0296.1

Average sea-level pressure field (in hPa) corresponding to the most unpredictable situations (high dimensions).

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