Thursday 14 Dec 2017: Extreme heat waves sampled through large deviation algorithms (Joint Astrophysics/GAFD Seminar)
Prof. Freddy Bouchet - ENS-Lyon, France
For some aspects of climate dynamics, rare dynamical events may play a key role, for instance when they have a huge impact. We will study the paradigmatic example of extreme heat waves. In the recent past, new theoretical and numerical tools have been developed in the statistical mechanics community, in order to specifically study such rare events. Some of those approaches are based on large deviation theory for complex dynamical systems.
We will study the probability of extreme heat waves in a comprehensive GCM. At a fixed numerical cost, several hundreds more heat waves are observed than in a control run. The thousands of sampled extreme heat waves open the door to their dynamical studies, precursor, and fluctuation paths, in a way that can not be foreseen using conventional tools based on direct numerical simulations. Moreover extreme events that can not be observed in a GCM at a reasonable cost can now be studied. This new tool opens new perspectives for the study of climate extremes. As an example we discuss teleconnection patterns for extremes.
(Authors: Freddy Bouchet, Francesco Ragone and Jeroen Wouters. ENS de Lyon et CNRS)