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Lookup NU author(s): Dr Celine Guervilly
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).
We study rapidly rotating Boussinesq convection driven by internal heating in a full sphere. We use a numerical model based on the quasi-geostrophic approximation for the velocity field, whereas the temperature field is 3-D. This approximation allows us to perform simulations for Ekman numbers down to 10−8, Prandtl numbers relevant for liquid metals (~10−1) and Reynolds numbers up to 3x104. Persistent zonal flows composed of multiple jets form as a result of the mixing of potential vorticity. For the largest Rayleigh numbers computed, the zonal velocity is larger than the convective velocity despite the presence of boundary friction. The convective structures and the zonal jets widen when the thermal forcing increases. Prograde and retrograde zonal jets are dynamically different: in the prograde jets (which correspond to weak potential vorticity gradients) the convection transports heat efficiently and the mean temperature tends to be homogenized; by contrast, in the cores of the retrograde jets (which correspond to steep gradients of potential vorticity) the dynamics is dominated by the propagation of Rossby waves, resulting in the formation of steep mean temperature gradients and the dominance of conduction in the heat transfer process. Consequently, in quasi-geostrophic systems, the width of the retrograde zonal jets controls the efficiency of the heat transfer.
Author(s): Guervilly C, Cardin P
Publication type: Article
Publication status: Published
Journal: Geophysical Journal International
Year: 2017
Volume: 211
Issue: 1
Pages: 455-471
Print publication date: 01/10/2017
Online publication date: 28/07/2017
Acceptance date: 27/07/2017
Date deposited: 04/09/2017
ISSN (print): 0956-540X
ISSN (electronic): 1365-246X
Publisher: Oxford University Press
URL: https://doi.org/10.1093/gji/ggx315
DOI: 10.1093/gji/ggx315
Notes: pdf available on arxiv: https://arxiv.org/abs/1708.05342
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