The typicality and spatio-temporal structure of extreme climate regimes revealed through Archetype Analysis

Dr. Chris Chapman, Senior Research Scientist, CSIRO Environment, Hobart Marine Laboratories, Castray Esplanade, Hobart, Tasmania.

We present a new perspective on the "regimes" (persistent and recurring climate states) associated with temperature extremes by using an advanced data-mining technique, Archetype Analysis, to directly identify large-scale extreme states. In contrast to studies that link regional extremes to the large-scale by first identifying events at one or more individual locations, then zoom-out to investigate the large scale patterns (an approach that we refer to as "inside-out"), our approach starts by extracting extreme configurations of the system at the largest spatial scales, then zooming in to investigate the influence of these extreme regimes on regional conditions. As such, we call our approach "outside-in".

 An application of the method will be  presented: the link between the hemispheric-scale atmospheric circulation and terrestrial heatwaves in the northern hemisphere. We show that the most devastating heatwave events (such as the 2010 "Russian heatwave" or the 2023 North American "heat dome") can be represented by only a few different recurring and persistent regimes. We apply standard statical metrics, such as the return period, to show that although individual events are rare, the large-scale regimes the produce them are, in fact, typical, with fairly regular recurrance.

Bio: Chris Chapman is a Senior Research Scientist with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Australia's national science agency. He is primarily a physical oceanographer, but is trained in meteorology and spent several years as an operational weather forecaster. His primary interests are atmosphere-ocean interaction in the tropics and western boundary current regions, and understanding the role of the ocean in extreme climate and weather events, such as heatwaves and tropical cyclones. He is on sabbatical at TU Delft until July 2025. 

References:

Chapman et al. 2023, A large-scale view of marine heatwaves revealed by archetype analysis: https://doi.org/10.1038/s41467-022-35493-x

Chapman et al. 2025 The Typicality of Regimes Associated with Northern Hemisphere Heatwaves (preprint): https://doi.org/10.48550/arXiv.2410.12179