Effects of forcing scale and intensity on the emergence and maintenance of polar vortices on Saturn and Ice Giants

Brueshaber, Shawn; Sayanagi, Kunio M.

doi:10.1016/j.icarus.2021.114386

Cited by 8 publications

(27 citation statements)

References 25 publications

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“…Planetary Burger number. Here, we explore how our results compare with previous modelling studies [8][9][10][11] , which computed a planetary Burger number Bu = L 2 d /2a 2 , with L d an internal Rossby radius of deformation and a the planetary radius. Using an upper limit value of L d = 1,600 km (that is, the size of the largest baroclinic eddies) yields Bu = 2.6 × 10 −4 , corresponding to a regime with multiple circumpolar cyclones 9,10 and hence comparing favourably with refs [8][9][10][11] .…”

Section: Available Potential Energymentioning

confidence: 85%

“…Lightning reported at northern latitudes in recent studies [5][6][7] , especially above the 2-bar level 7 , points to moist convection within ammonia clouds as a powerful source of energy in Jupiter's polar regions. However, even though the dynamical link between small-scale moist convection and large-scale vortices has been investigated at high latitudes in recent modelling studies [8][9][10][11] , it has never been supported by observations.…”

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confidence: 99%

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Moist convection drives an upscale energy transfer at Jovian high latitudes

et al. 2022

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Jupiter’s atmosphere is one of the most turbulent places in the solar system. Whereas observations of lightning and thunderstorms point to moist convection as a small-scale energy source for Jupiter’s large-scale vortices and zonal jets, this has never been demonstrated due to the coarse resolution of pre-Juno measurements. The Juno spacecraft discovered that Jovian high latitudes host a cluster of large cyclones with diameter of around 5,000 km, each associated with intermediate- (roughly between 500 and 1,600 km) and smaller-scale vortices and filaments of around 100 km. Here, we analyse infrared images from Juno with a high resolution of 10 km. We unveil a dynamical regime associated with a significant energy source of convective origin that peaks at 100 km scales and in which energy gets subsequently transferred upscale to the large circumpolar and polar cyclones. Although this energy route has never been observed on another planet, it is surprisingly consistent with idealized studies of rapidly rotating Rayleigh–Bénard convection, lending theoretical support to our analyses. This energy route is expected to enhance the heat transfer from Jupiter’s hot interior to its troposphere and may also be relevant to the Earth’s atmosphere, helping us better understand the dynamics of our own planet.

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Section: Available Potential Energymentioning

confidence: 85%

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confidence: 99%

Moist convection drives an upscale energy transfer at Jovian high latitudes

et al. 2022

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“…Likewise, retrieved horizontal wind fields only apply to a limited altitude range compared to the full vertical extent of the vortex. Subject to these types of limitations, vortex models constrained by imaging and wind field data have been extensively used to estimate atmospheric static stability on Jupiter, with many finding a deformation radius of about 2,000 km (e.g., Brueshaber & Sayanagi, 2021; Brueshaber et al., 2019; Cho et al., 2001; Shetty & Marcus, 2010).…”

Section: Discussionmentioning

confidence: 99%

Evolution of the Horizontal Winds in Jupiter's Great Red Spot From One Jovian Year of HST/WFC3 Maps

Wong

Marcus

Simon-Miller

et al. 2021

Geophysical Research Letters

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The Great Red Spot is an enduring large anticyclone in Jupiter's atmosphere, situated in the South Tropical Zone (Figure 1). Anticyclonic flow in this zone is perturbed over the northern edge of the GRS so that it locally protrudes into the typically dark and reddish South Equatorial Belt (SEB) to the north. The SEB features dramatic global-scale changes in coloration, cloud properties, and convective activity (e.g., Fletcher et al., 2011Fletcher et al., , 2017Rogers, 1995;Sánchez-Lavega & Gómez, 1996), but the most notable change in the GRS itself is more monotonic in nature: a continuous decrease in size over more than 100 years of accurate observations (Simon et al., 2018).The size and longevity of the GRS make it unique among outer solar system vortices, yet it also serves as an archetype of a class of "pancake vortices"-anticyclones embedded in stably stratified fluids-also including vortices like the dark spots on Neptune and salt lens eddies in the Earth's oceans (e.g., Dowling, 1995;Hassanzadeh et al., 2012;Yim et al., 2016). Pancake vortices have a thickness much smaller than their horizontal dimensions, like the GRS whose horizontal scale is some 50 times greater than vertical scale, according to theoretical arguments based on laboratory experiments and Jovian vortex velocity fields (Lemasquerier et al., 2020). Terrestrial ocean eddies transport heat meridionally by both stirring (turbulent) and trapping (bulk transport) mechanisms (Sun et al., 2018). Trapping is limited on Jupiter because major vortices are bounded by jets that limit meridional migration, although trapping could be significant on Saturn, where poleward migration of the anticyclone created by the 2010 Great White Storm was observed

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“…The highest resolution achieved in their model was 512 2 (Δx ≈ 150 km), which is sufficient for stable evolution but not enough to resolve the detailed behavior of the large cyclonic and anticyclonic regions with increasingly low deformation length. Previous works have generally explored the poles of Jupiter and Saturn with a resolution of 256 2 -512 2 (e.g., Morales-Juberías et al 2011O'Neill et al 2015;Brueshaber & Sayanagi 2021); for Jupiter size scales, such resolutions correspond to Δx = 150-300 km. Our model takes the base resolution further by exploring Jupiter's dynamics with a resolution of 1024 2 (Δx = 75 km, 4× more resolution in area than previous shallow water models), which proves necessary to study the long-term effects of the lowest deformation lengths and resolved forcing scales that might be dynamically relevant for atmospheric evolution.…”

Section: Model Descriptionmentioning

confidence: 99%

“…They quantified the effects of the cyclone-toanticyclone ratio, storm strength, and planetary Burger number, Bu, on the long-term evolution of their models and found Bu to be the most important dimensionless parameter that characterizes the primary mode of the dynamics. Brueshaber & Sayanagi (2021) further explored the Bu values relevant for Saturn and Saturn-like systems to study the detailed behavior of emergent large-scale polar cyclones that dominate most of the polar region.…”

Section: Introductionmentioning

confidence: 99%

Exploring Jupiter's Polar Deformation Lengths with High-resolution Shallow Water Modeling

Hyder¹,

Lyra²,

Chanover³

et al. 2022

Planet. Sci. J.

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The polar regions of Jupiter host a myriad of dynamically interesting phenomena, including vortex configurations, folded-filamentary regions (FFRs), and chaotic flows. Juno observations have provided unprecedented views of the high latitudes, allowing for more constraints to be placed upon the troposphere and the overall atmospheric energy cycle. Moist convective events are believed to be the primary drivers of energetic storm behavior as observed on the planet. Here we introduce a novel single-layer shallow water model to investigate the effects of polar moist convective events at high resolution, the presence of dynamical instabilities over long timescales, and the emergence of FFRs at high latitudes. We use a flexible, highly parallelizable, finite difference hydrodynamic code to explore the parameter space set up by previous models. We study the long-term effects of deformation length (L d ), injected pulse size, and injected geopotential. We find that models with L d beyond 1500 km (planetary Burger number, Bu = 4.4 × 10−4) tend to homogenize their potential vorticity in the form of dominant stable polar cyclones, while lower-L d cases tend to show less stability with regard to Arnol’d-type flows. We also find that large turbulent forcing scales consistently lead to the formation of high-latitude FFRs. Our findings support the idea that moist convection occurring at high latitudes may be sufficient to produce the dynamical variety seen at the Jovian poles. Additionally, derived values of localized horizontal shear and L d may constrain FFR formation and evolution.

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Effects of forcing scale and intensity on the emergence and maintenance of polar vortices on Saturn and Ice Giants

Cited by 8 publications

References 25 publications

Moist convection drives an upscale energy transfer at Jovian high latitudes

Moist convection drives an upscale energy transfer at Jovian high latitudes

Evolution of the Horizontal Winds in Jupiter's Great Red Spot From One Jovian Year of HST/WFC3 Maps

Exploring Jupiter's Polar Deformation Lengths with High-resolution Shallow Water Modeling

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