Atmosphere Ocean Science Friday Seminar

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Baroclinic Turbulence Above Rough Topography

Speaker: Matt Pudig

Location: Warren Weaver Hall 1314

Date: Friday, April 5, 2024, 4 p.m.

Synopsis:

Much has been understood about baroclinic turbulence in the ocean and atmosphere through the study of the two-layer quasi-geostrophic (QG) model, and much about this model is now well understood. Recent scaling theories for the eddy fluxes in the fully-developed turbulence of this model, however, assume a flat bottom boundary. In this talk, I will discuss an organizing principle for how rough topography (i.e., topography with length scales similar to or smaller than those of the eddies) modifies the statistically equilibrated state of baroclinic turbulence. In particular, I will focus on the effects of random, monoscale topography in the two-layer QG model on an f-plane, forced by a mean zonal shear and dissipated by linear Ekman drag. I will present a large set of numerical simulations that systematically modify the topographic length and height scales, and provide a survey of the dependence of the eddy diffusivity and eddy mixing length on the two nondimensional parameters of the system. I will show how a novel control parameter – a function of the two nondimensional parameters – delineates two regimes: the previously described “vortex gas” regime, which holds in both the flat bottom and small topographic height regime, and a topographically-controlled regime. I will then demonstrate how this theory extends to more realistic, multiscale topography. Finally, I will discuss how spectral energy budgets reveal that the energy pathways of two-layer QG turbulence are importantly reorganized in the topographically-controlled regime as compared to the energy pathways in the flat bottom limit.