Abstract
Abstract. Atmospheric jet streams are typically separated into primarily “eddy-driven” (or polar-front) jets and primarily “thermally driven” (or subtropical) jets. Some regions also display “merged” jets, resulting from the (quasi-)collocation of the regions of eddy generation with the subtropical jet. The different locations and driving mechanisms of these jets arise from very different underlying mechanisms and result in very different jet characteristics. Here, we link the current understanding of dynamical jet maintenance mechanisms, mostly arising from conceptual or idealized models, to the phenomena observed in reanalysis data. We specifically focus on developing a unitary analysis framework grounded in dynamical systems theory, which may be applied to both idealized models and reanalysis, as well as allowing for direct intercomparison. Our results illustrate the effectiveness of dynamical systems indicators to diagnose jet regimes.
Highlights
The global atmospheric circulation may be construed as arising from the three-way interaction between the mean meridional circulation, mid-latitude zonal jet streams and baroclinically unstable eddies
We focus on developing a unitary analysis framework which may be applied to both the idealized model and reanalysis data, allowing for direct intercomparison
The model setup, radiative equilibrium profile and fixed parameter values used here are the same as in Lachmy and Harnik (2016) and are provided in Appendix A. These are meant to mimic wintertime conditions. Both in the model and in the reanalysis data (Sect. 2.2), on the Southern Hemisphere (SH) because it is closer to zonal symmetry than its northern counterpart
Summary
The global atmospheric circulation may be construed as arising from the three-way interaction between the mean meridional circulation, mid-latitude zonal jet streams and baroclinically unstable eddies. Recent advances in dynamical systems theory have demonstrated that any instantaneous state of a chaotic system may be described by two metrics: the local dimension – related to the system’s active degrees of freedom around that particular state – and a local measure of persistence (Lucarini et al, 2016; Faranda et al, 2017b) This approach can be applied to a variety of datasets, including suitably processed reanalysis data, and may be used to provide a direct analogy between modelled and observed flows. We discuss these results in the context of both idealized models and studies of the observed atmospheric jet, and we draw our conclusions in Sect.
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