Computation of extreme heat waves in climate models using a large deviation algorithm

Francesco Ragone (1, 2) , Jeroen Wouters (3, 1, 4) , Freddy Bouchet (1)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
2 DISAT - Dipartimento di Scienze dell'Ambiente e del Territorio
3 School of Mathematics and statistics [Sydney]
4 Meteorologisches Institut [Hamburg]

Studying extreme events and how they evolve in a changing climate is one of the most important current scientific challenges. Starting from complex climate models, a key difficulty is to be able to run long enough simulations in order to observe those extremely rare events. In physics, chemistry, and biology, rare event algorithms have recently been developed to compute probabilities of events that cannot be observed in direct numerical simulations. Here we propose such an algorithm, specifically designed for extreme heat or cold waves, based on statistical physics approaches. This gives an improvement of more than two orders of magnitude in the sampling efficiency. We describe the dynamics of events that would not be observed otherwise. We show that European extreme heat waves are related to a global teleconnection pattern involving North America and Asia. This tool opens a full range of studies, so far impossible, aimed at assessing quantitatively climate change impacts.

Mots clés: Large deviation theory; Rare event algorithms; Statistical physics; Climate extreme events; Heat waves

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]; Physique Numérique [physics.comp-ph]; Dynamique Chaotique [nlin.CD]

Francesco Ragone, Jeroen Wouters, Freddy Bouchet. Computation of extreme heat waves in climate models using a large deviation algorithm. Proceedings of the National Academy of Sciences of the United States of America, 2018, 115 (1), pp.24-29. ⟨10.1073/pnas.1712645115⟩. ⟨hal-01584944v2⟩