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

Bardet, Deborah; Spiga, Aymeric; Guerlet, Sandrine; Cabanes, Simon; Millour, Ehouarn; Boissinot, Alexandre

doi:10.1016/j.icarus.2020.114042

Cited by 18 publications

(22 citation statements)

References 63 publications

(123 reference statements)

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“…of heat via adiabatic expansion/compression. Guerlet et al (2014) developed the RC model that was incorporated into the GCM of Spiga et al (2020), itself extended to the upper stratosphere in Bardet et al (2021) -we show the RC estimates of seasonal temperatures here. In both cases, the spatial distributions of hydrocarbons were treated as latitudinally and temporally uniform, and the influence of stratospheric aerosols, which can cause increased stratospheric temperatures of 5-6 K (Guerlet et al, 2015), was not considered.…”

Section: Simulating Seasonal Variabilitymentioning

confidence: 99%

Saturn's Seasonal Atmosphere at Northern Summer Solstice

Fletcher¹,

Sromovsky²,

Hue³

et al. 2020

Preprint

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The incredible longevity of Cassini's orbital mission at Saturn has provided the most comprehensive exploration of a seasonal giant planet to date. This review explores Saturn's changing global temperatures, composition, and aerosol properties between northern spring and summer solstice (2015-2017), extending our previous review of Cassini's remote sensing investigations (2004( -2014( , Fletcher et al., 2018c to the grand finale. The result is an unprecedented record of Saturn's climate that spans almost half a Saturnian year, which can be used to test the seasonal predictions of radiative climate models, neutral and ion photochemistry models, and atmospheric circulation models. Hemi-

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Section: Simulating Seasonal Variabilitymentioning

confidence: 99%

Saturn's Seasonal Atmosphere at Northern Summer Solstice

Fletcher¹,

Sromovsky²,

Hue³

et al. 2020

Preprint

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“…In addition, systematic infrared observations of long timescales led to the discovery of stratospheric quasi-periodic oscillations manifested in the stratospheric temperatures and winds, in particular the quasi-quadrennial oscillation (QQO) in Jupiter (Orton et al 1991) as well as the Saturn equatorial oscillation (SEO; Orton et al 2008). These oscillations have been the subject of numerous follow-up observations and modeling efforts to obtain robust constraints on their origin and evolution (Cosentino et al 2017;Li & Read 2000;Medvedev et al 2013;Spiga et al 2020;Bardet et al 2021;Giles et al 2020;Antuñano et al 2020). However, deriving the wind field from the thermal wind balance is only an approximation, which in addition breaks down at the equator.…”

Section: Introductionmentioning

confidence: 99%

First direct measurement of auroral and equatorial jets in the stratosphere of Jupiter

Cavalié

Benmahi

Hue

et al. 2021

A&A

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Context. The tropospheric wind pattern in Jupiter consists of alternating prograde and retrograde zonal jets with typical velocities of up to 100 m s−1 around the equator. At much higher altitudes, in the ionosphere, strong auroral jets have been discovered with velocities of 1−2 km s−1. There is no such direct measurement in the stratosphere of the planet. Aims. In this Letter, we bridge the altitude gap between these measurements by directly measuring the wind speeds in Jupiter’s stratosphere. Methods. We use the Atacama Large Millimeter/submillimeter Array’s very high spectral and angular resolution imaging of the stratosphere of Jupiter to retrieve the wind speeds as a function of latitude by fitting the Doppler shifts induced by the winds on the spectral lines. Results. We detect, for the first time, equatorial zonal jets that reside at 1 mbar, that is, above the altitudes where Jupiter’s quasi-quadrennial oscillation occurs. Most noticeably, we find 300−400 m s−1 nonzonal winds at 0.1 mbar over the polar regions underneath the main auroral ovals. They are in counterrotation and lie several hundred kilometers below the ionospheric auroral winds. We suspect them to be the lower tail of the ionospheric auroral winds. Conclusions. We directly detect, for the first time, strong winds in Jupiter’s stratosphere. They are zonal at low-to-mid latitudes and nonzonal at polar latitudes. The wind system found at polar latitudes may help increase the efficiency of chemical complexification by confining the photochemical products in a region of large energetic electron precipitation.

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“…Planetary and gravity waves were first proposed as the cause of the Earth QBO by Lindzen & Holton (1968) and have since been proposed as causes of the Jupiter and Saturn oscillations as well (Friedson 1999;Li & Read 2000;Flasar et al 2004;Cosentino et al 2017;Bardet et al 2021). On Earth, momentum transfer from the waves to the zonal wind results in downward propagation of the wind velocity peaks.…”

Section: Introductionmentioning

confidence: 99%

Mapping the zonal winds of Jupiter’s stratospheric equatorial oscillation

Benmahi

Cavalié

Greathouse

et al. 2021

A&A

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Context. Since the 1950s, quasi-periodic oscillations have been studied in the terrestrial equatorial stratosphere. Other planets of the Solar System present (or are expected to present) such oscillations; for example the Jupiter equatorial oscillation and the Saturn semi-annual oscillation. In Jupiter’s stratosphere, the equatorial oscillation of its relative temperature structure about the equator is characterized by a quasi-period of 4.4 yr. Aims. The stratospheric wind field in Jupiter’s equatorial zone has never been directly observed. In this paper, we aim to map the absolute wind speeds in Jupiter’s equatorial stratosphere in order to quantify vertical and horizontal wind and temperature shear. Methods. Assuming geostrophic equilibrium, we apply the thermal wind balance using almost simultaneous stratospheric temperature measurements between 0.1 and 30 mbar performed with Gemini/TEXES and direct zonal wind measurements derived at 1 mbar from ALMA observations, all carried out between March 14 and 22, 2017. We are thus able to self-consistently calculate the zonal wind field in Jupiter’s stratosphere where the JEO occurs. Results. We obtain a stratospheric map of the zonal wind speeds as a function of latitude and pressure about Jupiter’s equator for the first time. The winds are vertically layered with successive eastward and westward jets. We find a 200 m s−1 westward jet at 4 mbar at the equator, with a typical longitudinal variability on the order of ~50 m s−1. By extending our wind calculations to the upper troposphere, we find a wind structure that is qualitatively close to the wind observed using cloud-tracking techniques. Conclusions. Almost simultaneous temperature and wind measurements, both in the stratosphere, are a powerful tool for future investigations of the JEO (and other planetary equatorial oscillations) and its temporal evolution.

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

Cited by 18 publications

References 63 publications

Saturn's Seasonal Atmosphere at Northern Summer Solstice

Saturn's Seasonal Atmosphere at Northern Summer Solstice

First direct measurement of auroral and equatorial jets in the stratosphere of Jupiter

Mapping the zonal winds of Jupiter’s stratospheric equatorial oscillation

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