The 2015 Lewis Fry Richardson Medal is awarded to Daniel Schertzer for initiating innovative ideas in nonlinear geophysics, in particular the multifractal formalism, the concept of generalised scale invariance, and their implementation in data analyses leading to a reinterpretation of long-standing problems in hydrology and atmospheric sciences.
Daniel Schertzer is a scientific leader at the forefront of interdisciplinary research at the interface of hydrological, atmospheric and mathematical sciences. He has actively developed new synergies with far-reaching consequences. He is especially known for his pioneering theoretical works on multifractals and generalised scale invariance in geophysics. He brought mathematical coherence and physically insightful analysis to geophysical data with the help of innovative concepts, such as multifractal predictability (his AGU Lorenz Lecture in 2008), multifractal universality and phase transitions. His related work on fractional Fokker-Planck equations for stochastic systems driven by non-Gaussian Levy noises has been widely recognised.
Schertzer has been at the origin of new, fresh ideas in geophysics: a complex field such as rainfall can be understood and simulated with the help of the symmetries of the generating equations, instead of truncating and oversimplifying the latter. This change of paradigm took hold on the concept of generalised scale invariance designed to overcome the limitations of the classical approach that posits first isotropy, then scaling and which can be traced back to Kolmogorov’s concept of local isotropy. This led to a rather straightforward solution to the crisis of the classical scheme of atmospheric dynamics (quasi-two-dimensional large scale and quasi-three-dimensional small scale behaviours). In so doing, he has created powerful tools to investigate multifractality of differential systems, a significant example being his scaling alternative to the classical quasi-geostrophic approximation.
The empirical relevance of his theoretical works is highlighted in his recent book, The Weather and Climate: Emergent Laws and Multifractal Cascades, co-authored with Shaun Lovejoy and published in 2013 by Cambridge University Press. Schertzer has built-up long lasting collaborations to bring empirical evidence to his theoretical breakthroughs and has been very active to service the scientific community. During the recent period he has been contributing to the challenging interface between geophysics and societal issues, notably on the strategic questions of hydrology, rainfall and floods, wind energy, resilient cities and climate change.
Based on his accomplishments and on the wide array of applications that his research has led to, Daniel Schertzer is a worthy recipient of the 2015 EGU Lewis Fry Richardson Medal.