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SUMMARY:Inhomogeneity and anisotropy in planetary turbulence: zonostrophy 
 and beyond? - Peter Leonard Read (University of Oxford)
DTSTART:20220106T153000Z
DTEND:20220106T163000Z
UID:TALK166435@talks.cam.ac.uk
DESCRIPTION:Theoretical approaches to understanding and quantifying the pr
 operties of turbulence have traditionally started with assumptions of homo
 geneity and isotropy of flow structure and/or forcing and dissipation. But
  realistic flows seldom satisfy such assumptions. In a planetary atmospher
 e\, flows are forced primarily by buoyancy contrasts on both large and sma
 ll scales\, leading to both large scale overturning and localised patches 
 of convective turbulence that are far from homogeneous. Flow structure is 
 also strongly influenced by stratification and background rotation\, leadi
 ng to highly anisotropic behaviours in the form of layered structures and 
 strong zonal jets. In an attempt to understand the influence of rotation o
 n large-scale planetary turbulence\, the concept of the zonostrophic regim
 e was proposed some 15 years ago by Galperin and Sukoriansky. This concept
  takes direct account of the non-local upscale transfers of kinetic energy
  by large-scale waves\, leading to a pattern of zonally symmetric jets wit
 h a characteristic universal spatial spectrum. The zonal flows coexist wit
 h a non-axisymmetric turbulent flow that participates in a more convention
 al Kolmogorov-Kraichnan local inverse energy cascade on scales larger than
  the principal forcing of barotropic modes. Observations and models of atm
 ospheres\, oceans and planetary interiors\, and also some laboratory exper
 iments\, are partly consistent with the zonostrophic regime\, but with som
 e marked discrepancies. However\, the zonostrophic concept only applies to
  the barotropic component of the flow\, leaving unaddressed the role of st
 ratification in both the forcing of large-scale turbulence and the structu
 re and characteristics of scales smaller than the forcing scale. Observati
 ons indicate the presence of a direct energy cascade at small scales\, eve
 n at scales expected to be anisotropic due to either rotation or stratific
 ation. Elucidating the nature of this transition from inverse to direct ca
 scade at decreasing scales is one of the key challenges to our understandi
 ng of planetary turbulence in atmospheres\, oceans and planetary interiors
 .&nbsp\;
LOCATION:Seminar Room 1\, Newton Institute
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