Group seminar on 4. July, 16:15 CET
Ocean rogue waves and extremes of the Lorenz-2005 model
Prof. Dr. Francesco Fedele
I present a general theory of space-time extremes for the stochastic description of oceanic rogue waves and its application to describe extremes of the Lorenz-2005 model. First, I present results on the nature of rogue wave formation by analyzing a novel data set of high-frequency laser altimeter measurements of the sea-surface elevation gathered over a period of 18 years from 2003 to 2020 on the offshore ‘Ekofisk’ platform in the central North Sea.The wave record includes ~27500 measured sea states of 30-min duration. The rogue waves observed, including the Andrea wave, present sharper crests and shallower troughs well described by second order bound nonlinearities.
Then, I introduce the continuum limit of the Lorenz-2005 model and discuss the long-term dynamics near the unstable fixed point described by a Ginzburg-Landau equation. The statistics of extremes of the Lorenz model are then discussed in the context of space-time extremes. In absence of dissipation and forcing, the Lorenz model conserves energy, except the momentum. It is not Hamiltonian since the Jacobi identity is not satisfied. A class of models derived from the original parent Lorenz model that conserve both quantities and are Hamiltonian are finally discussed. This is joint work with Cristal Chandre, Martin Horvat and Nedjeljka Zagar.