Music of the stratospheres

Dowling, T. E.

doi:10.1038/453163a

Cited by 8 publications

(8 citation statements)

References 7 publications

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“…Cassini measurements even enabled to link a disruption in the downward propagation of the equatorial oscillation to the 2010 Great White Spot occurrence . Analogies can be drawn between Saturn's and the Earth's stratospheres (Dowling, 2008). Saturn's equatorial oscillation is reminiscent of Earth's Quasi-Biennal Oscillation and Semi-Annual Oscillation (Andrews et al, 1987;Baldwin et al, 2001;Lott and Guez, 2013;Guerlet et al, 2018), driven by the propagation and breaking of Rossby, Kelvin and inertio-gravity waves.…”

Section: Introductionmentioning

confidence: 99%

Global climate modeling of Saturn's atmosphere. Part II: Multi-annual high-resolution dynamical simulations

Spiga

Guerlet

Millour

et al. 2020

Icarus

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Highlights• A new Global Climate Model for Saturn with radiative transfer • High-resolution numerical simulations on a duration of 15 Saturn years • Results on zonal jets, waves, eddies in Saturn's troposphere AbstractThe Cassini mission unveiled the intense and diverse activity in Saturn's atmosphere: banded jets, waves, vortices, equatorial oscillations. To set the path towards a better understanding of those phenomena, we performed high-resolution multi-annual numerical simulations of Saturn's atmospheric dynamics. We built a new Global Climate Model [GCM] for Saturn, named the Saturn DYNAMICO GCM, by combining a radiative-seasonal model tailored for Saturn to a hydrodynamical solver based on an icosahedral grid suitable for massively-parallel architectures. The impact of numerical dissipation, and the conservation of angular momentum, are examined in the model before a reference simulation employing the Saturn DYNAMICO GCM with a 1/2 • latitude-longitude resolution is considered for analysis. Mid-latitude banded jets showing similarity with observations are reproduced by our model. Those jets are accelerated and maintained by eddy momentum transfers to the mean flow, with the magnitude of momentum fluxes compliant with the observed values. The eddy activity is not regularly distributed with time, but appears as bursts; both barotropic and baroclinic instabilities could play a role in the eddy activity. The steady-state latitude of occurrence of jets is controlled by poleward migration during the spin-up of our model. At the equator, a weaklysuperrotating tropospheric jet and vertically-stacked alternating stratospheric jets are obtained in our GCM simulations. The model produces Yanai (Rossby-gravity), Rossby and Kelvin waves at the equator, as well as extratropical Rossby waves, and large-scale vortices in polar regions. Challenges remain to reproduce Saturn's powerful superrotating jet and hexagon-shaped circumpolar jet in the troposphere, and downward-propagating equatorial oscillation in the stratosphere.

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Section: Introductionmentioning

confidence: 99%

Global climate modeling of Saturn's atmosphere. Part II: Multi-annual high-resolution dynamical simulations

Spiga

Guerlet

Millour

et al. 2020

Icarus

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“…The longevity of the Cassini mission permitted an unprecedented spatial and seasonal coverage of Saturn's stratosphere. In particular, the Composite InfraRed Spectrometer (CIRS) instrument on board Cassini revealed stratospheric phenomena analogous to ones occurring in Earth's and Jupiter's stratospheres (Dowling, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Despite differences in their periods, Jupiter's and Saturn's equatorial oscillations share similarities with the Earth's (Dowling, 2008), which raises questions about the driving mechanisms of the gas giants' equatorial oscillations. Building on tools developed throughout the long history of Earth's atmospheric modeling, numerical models of global circulation on Jupiter and Saturn have been developed for almost 20 years.…”

Section: Introductionmentioning

confidence: 99%

Global climate modeling of Saturn’s atmosphere. Part IV: Stratospheric equatorial oscillation

Bardet

Spiga

Guerlet

et al. 2021

Icarus

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The Composite InfraRed Spectrometer (CIRS) on board Cassini revealed an equatorial oscillation of stratospheric temperature, reminiscent of the Earth's Quasi-Biennial Oscillation (QBO), as well as anomalously high temperatures under Saturn's rings. To better understand these predominant features of Saturn's atmospheric circulation in the stratosphere, we have extended to the upper stratosphere the DYNAMICO-Saturn global climate model (GCM), already used in a previous publication to study the tropospheric dynamics, jets formation and planetary-scale waves activity. Firstly, we study the higher model top impact on the tropospheric zonal jets and kinetic energy distribution. Raising the model top prevents energy and enstrophy accumulation at tropopause levels. The reference GCM simulation with 1/2 • latitude/longitude resolution and a raised model top exhibits a QBO-like oscillation produced by resolved planetary-scale waves. However, the period is more irregular and the downward propagation faster than observations. Furthermore, compared to the CIRS temperature retrievals, the modeled QBO-like oscillation underestimates by half both the amplitude of temperature anomalies at the equator and the vertical characteristic length of this equatorial oscillation. This QBO-like oscillation is mainly driven by westward-propagating waves; a significant lack of eastward waveforcing explains a fluctuating eastward phase of the QBO-like oscillation. We also show that the seasonal cycle of Saturn is a key parameter of the establishment and the regularity of the equatorial oscillation. At 20 • N and 20 • S latitudes, the DYNAMICO-Saturn GCM exhibits several strong seasonal eastward jets, alternatively in the northern and southern hemisphere. These jets are correlated with the rings' shadowing. Using a GCM simulation without rings' shadowing, we show its impact on Saturn's stratospheric dynamics. Both residualmean circulation and eddy forcing are impacted by rings' shadowing. In particular, the QBO-like oscillation is weakened by an increased drag caused by those two changes associated with rings' shadowing.

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“…First, an unexpected periodicity disruption of QBO on Earth was reported in 2016 (Newman et al ., 2016; Osprey et al ., 2016), triggering debates on the origin of this effect (Dunkerton, 2016). Second, QBO‐like phenomena have been reported in other planetary atmospheres (Dowling, 2008; Read, 2018), and is suspected to occur in stably stratified layers in stars (McIntyre, 1994; Kim and MacGregor, 2001; Rogers and Glatzmaier, 2006; Rogers et al ., 2008; Showman et al ., 2019). Third, fluid dynamicists have shed new light on the interplay between waves, mean flow and sometimes turbulence in stratified fluids: the nature of the bifurcation towards an oscillating state in HLP's model when the control parameter Re is varied has been elucidated and tested against laboratory experiments (Yoden and Holton, 1988; Semin et al ., 2018); the possibility for synchronization or phase‐locking with a seasonal cycle have been investigated within the HLP framework (Rajendran et al ., 2015); emergence of low‐frequency mean‐flow reversals in a stably stratified layer forced by a turbulent layer have been reported in direct numerical simulations (Couston et al ., 2018); and secondary bifurcations with a quasi‐periodic route to chaos in mean‐flow reversals have been reported both in the HLP model (Kim and MacGregor, 2001; Renaud et al ., 2019) and direct numerical simulations (Renaud et al ., 2019).…”

Section: Introductionmentioning

confidence: 97%

On the Holton–Lindzen–Plumb model for mean flow reversals in stratified fluids

Renaud

Venaille

2020

Quart J Royal Meteoro Soc

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The Holton–Lindzen–Plumb (HLP) model describes the spontaneous emergence of mean flow reversals in stratified fluids. It has played a central role in understanding the Quasi‐Biennial Oscillation of equatorial winds in Earth's stratosphere and has arguably become a linchpin of wave–mean flow interaction theory in geophysical and astrophysical fluid dynamics. The derivation of the model's equation from primary equations follows from several assumptions, including quasi‐linear approximations, WKB expansion of the wavefield, simplifications of boundary‐layer terms, among others. Starting from the two‐dimensional, non‐rotating, Boussinesq equations, we present in this paper a self‐consistent derivation of the HLP model and show the existence of a distinguished limit for which all approximations remains valid. We furthermore discuss the important role of boundary conditions, and the relevance of this model to describe secondary bifurcations associated with a quasi‐periodic route to chaos.

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Music of the stratospheres

Cited by 8 publications

References 7 publications

Global climate modeling of Saturn's atmosphere. Part II: Multi-annual high-resolution dynamical simulations

Global climate modeling of Saturn's atmosphere. Part II: Multi-annual high-resolution dynamical simulations

Global climate modeling of Saturn’s atmosphere. Part IV: Stratospheric equatorial oscillation

On the Holton–Lindzen–Plumb model for mean flow reversals in stratified fluids

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