Semester 1, Week 9: Dr Lois Baker, University of Edinburgh

Academic webpage

Title: Untangling waves and mean flows via PDE-based Lagrangian filtering

Abstract: Oceanic flows are typically composed of wave and mean motions with a wide range of overlapping temporal scales, making separation between the two types of motion in wave resolving numerical simulations challenging. Lagrangian filtering – whereby a temporal filter is appliedin the frame of the flow – is an effective way to overcome this challenge, allowing clean separation of waves from mean flow based on frequency separation in a Lagrangian frame. In this talk, I will present an efficient method for finding the Lagrangian mean and associated wave component using online or offline low-pass filtering without particle tracking. This method is model-agnostic, but I’ll introduce a new package in Oceananigans (Julia software for fast, friendly, flexible, ocean-flavored fluid dynamics on CPUs and GPUs) that allows model output to be easily and efficiently processed to determine the wave and mean components. Finally, I’ll show some applications of this method.