Statistical State Dynamics of Weak Jets in Barotropic Beta-Plane Turbulence

Zonal jets in a barotropic setup emerge out of homogeneous turbulence through a flow-forming instability of the homogeneous turbulent state (zonostrophic instability), which occurs as the turbulence intensity increases. This has been demonstrated using the statistical state dynamics (SSD) framework...

Full description

Saved in:
Bibliographic Details
Published in:Journal of the atmospheric sciences 2019-03, Vol.76 (3), p.919-945
Main Authors: Bakas, Nikolaos A., Constantinou, Navid C., Ioannou, Petros J.
Format: Article
Language:English
Subjects:
Balancing
Barotropic mode
Beta-plane
Diffusion coefficient
Dynamic stability
Dynamics
Eddies
Equilibrium
Flow
Flow stability
Fluid dynamics
Homogeneous turbulence
Instability
Jet aircraft
Jets
Nonlinear dynamics
Phase transitions
Simulation
Statistics
Turbulence
Turbulence intensity
Turbulent flow
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Zonal jets in a barotropic setup emerge out of homogeneous turbulence through a flow-forming instability of the homogeneous turbulent state (zonostrophic instability), which occurs as the turbulence intensity increases. This has been demonstrated using the statistical state dynamics (SSD) framework with a closure at second order. Furthermore, it was shown that for small supercriticality the flow-forming instability follows Ginzburg–Landau (G–L) dynamics. Here, the SSD framework is used to study the equilibration of this flow-forming instability for small supercriticality. First, we compare the predictions of the weakly nonlinear G–L dynamics to the fully nonlinear SSD dynamics closed at second order for a wide range of parameters. A new branch of jet equilibria is revealed that is not contiguously connected with the G–L branch. This new branch at weak supercriticalities involves jets with larger amplitude compared to the ones of the G–L branch. Furthermore, this new branch continues even for subcritical values with respect to the linear flow-forming instability. Thus, a new nonlinear flow-forming instability out of homogeneous turbulence is revealed. Second, we investigate how both the linear flow-forming instability and the novel nonlinear flow-forming instability are equilibrated. We identify the physical processes underlying the jet equilibration as well as the types of eddies that contribute in each process. Third, we propose a modification of the diffusion coefficient of the G–L dynamics that is able to capture the evolution of weak jets at scales other than the marginal scale (side-band instabilities) for the linear flow-forming instability.
ISSN:0022-4928
1520-0469
DOI:10.1175/JAS-D-18-0148.1