GAFD Seminar: Daphne Lemasquerier

The colourful bands of Jupiter are sustained by intense east-west winds called zonal jets, which extend well below Jupiter's weather layer into its mantle of liquid hydrogen. These jets constitute a fascinating natural example of how a rapidly-rotating turbulent flow self-organises at large scale. Despite decades of observations and modelling, understanding the long-term, nonlinear equilibration of zonal jets and the feedback with the underlying turbulence and waves is still a challenge. In this seminar, I will present a combination of laboratory experiments and numerical and theoretical analyses to better understand the properties of zonal winds.

In the first part of the talk, I will adopt a "turbulence perspective". I will discuss the zonostrophic nature of the turbulent flow, and by analysing Lagrangian trajectories, I will discuss its transport properties in terms of an effective diffusivity. This part of the talk will be based on experimental results, cross-validated by complementary 2D quasi-geostrophic numerical simulations. In the second part of the talk, I will adopt a quasi-linear, "wave-mean flow interaction perspective". Following a similar approach as in the Holton-Lindzen-Plumb model for mean flow reversals in stratified fluids, I will describe a quasi-linear semi-analytical model to discuss the final equilibrium scale of zonal winds based on their feedback on Rossby waves.