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Abstract
The late-time behaviour of freely evolving quasi-geostrophic flows with initial characteristic length scale L0 larger than or equal to the deformation radius LD, L0/LD≥1 , is studied. At late time the flows are dominated by large multi-level vortices consisting of ascending terraces of well-mixed potential vorticity (PV), i.e. PV staircases. We examine how the number of mixed PV levels depends on the initial conditions, in particular L0/LD . For sufficiently large values of L0/LD≈5 , a complete staircase with regular steps forms, but as L0/LD decreases, the staircase becomes more irregular, with fewer mixed levels and the appearance of a large step centred on zero PV, corresponding to large regions of near-zero PV separating the multi-level vortices. This occurs because weak PV features in the initial field with scales smaller than LD undergo filamentation and are coarse-grained away or homogenised. For all values of L0/LD considered, inverse cascades of potential energy commence at sufficiently late times. The onset of these cascades, even when the flow is initialised well within the ‘asymptotic model’ (AM) regime, suggests that the AM regime is not self-consistent: when potential vorticity fronts are well-resolved, frontal dynamics eventually drive ongoing flow evolution.
Original language | English |
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Article number | A40 |
Number of pages | 16 |
Journal | Journal of Fluid Mechanics |
Volume | 939 |
Early online date | 1 Apr 2022 |
DOIs | |
Publication status | Published - 25 May 2022 |
Keywords
- Geostrophic turbulence
- Quasi-geostrophic flows
- Shallow water flows
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Dive into the research topics of 'Potential vorticity fronts and the late-time evolution of large-scale quasi-geostrophic flows'. Together they form a unique fingerprint.Projects
- 1 Finished
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Vortex Scaling and Universality: Vortex Scaling and Universality Far From Equilibrium
Burgess, H. (PI)
1/05/18 → 30/06/22
Project: Fellowship