%0 Journal Article
%T Global climate modeling of Saturn's atmosphere. Part III: Global statistical picture of zonostrophic turbulence in high-resolution 3D-turbulent simulations
%+ Laboratoire de Météorologie Dynamique (UMR 8539) (LMD)
%+ Institut Universitaire de France (IUF)
%A Cabanes, Simon
%A Spiga, Aymeric
%A Young, Roland M. B.
%< avec comité de lecture
%@ 0019-1035
%J Icarus
%I Elsevier
%V 345
%8 2020
%D 2020
%Z 2001.02473
%Z 2020Icar..34513705C
%R 10.1016/j.icarus.2020.113705
%K Global climate modeling
%K Zonostrophic regime
%K Saturn's zonal jets
%K Spectral analysis
%Z Sciences of the Universe [physics]Journal articles
%X We conduct an in-depth analysis of statistical flow properties calculated from the reference high-resolution Saturn simulation obtained by global climate modelling in Part II. In the steady state of this reference simulation, strongly energetic, zonally dominated, large-scale structures emerge, which scale with the Rhines scale. Spectral analysis reveals a strong anisotropy in the kinetic energy spectra, consistent with the zonostrophic turbulent flow regime. By computing spectral energy and enstrophy fluxes we confirm the existence of a double cascade scenario related to 2D-turbulent theory. To diagnose the relevant 3D dynamical mechanisms in Saturn's turbulent atmosphere, we run a set of four simulations using an idealized version of our Global Climate Model devoid of radiative transfer, with a well-defined Taylor-Green forcing and over several rotation rates (4, 1, 0.5, and 0.25 times Saturn's rotation rate). This allows us to identify dynamics in three distinctive inertial ranges: (1) a "residual-dominated" range, in which non-axisymmetric structures dominate with a -5/3 spectral slope; (2) a "zonostrophic inertial" range, dominated by axisymmetric jets and characterized by the pile-up of strong zonal modes with a steeper, nearly -3, spectral slope; and (3) a "large-scale" range, beyond Rhines' typical length scale, in which the reference Saturn simulation and our idealized simulations differ. In the latter range, the dynamics is dominated by long-lived zonal modes 2 and 3 when a Saturn-like seasonal forcing is considered (reference simulation), and a steep energetic decrease with the idealized Taylor-Green forcing. Finally, instantaneous spectral fluxes show the coexistence of upscale and downscale enstrophy/energy transfers at large scales, specific to the regime of zonostrophic turbulence in a 3D atmosphere.
%G English
%L insu-03726979
%U https://insu.hal.science/insu-03726979
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