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Exploring eddy ellipse geometry as metrics of eddy-mean flow interactions in a mixed instability jet Henderson, Connor James


Eddies have important feedbacks on the larger-scale flow and cannot be neglected in the description of the large-scale dynamics. GEOMETRIC is a promising framework for eddy parameterization that describes the eddy forcing in terms of the geometry of ellipses describing the eddy stress tensor. A systematic understanding of how the various geometric parameters describe and differentiate systems that include eddy forcing from barotropic versus baroclinic instability is needed to better understand how the geometric parameters should be prescribed. In this study, I use an idealized model of a western boundary current jet extension subject to both barotropic and baroclinic instabilities to understand how the various geometric parameters of the framework vary and relate to eddy-mean flow interaction (EMFI) dynamics. Specifically, I systematically vary the jet parameters to transition between a system dominated by barotropic instability to a system dominated by baroclinic instability to understand how this transition is recorded in the geometric terms. The geometric parameters show systematic differences between the barotropically-dominant and baroclinically-dominant case study runs, as well as across the full suite of runs. The geometric parameters also show systematic relationships to the EMFI metrics and vary across the suite of runs as the EMFI metrics vary. This work demonstrates that the geometric parameters can be useful for informing on EMFI dynamics and vice versa; the latter suggesting that there is potential to prescribe some aspects of the geometric parameter variability from knowledge of EMFI dynamics.

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