Temporal variations of Titan’s middle-atmospheric temperatures from 2004 to 2009 observed by Cassini/CIRS

Achterberg, R. K.; Gierasch, P. J.; Conrath, B. J.; Flasar, F. M.; Nixon, C. A.

doi:10.1016/j.icarus.2010.08.009

Cited by 89 publications

(154 citation statements)

References 42 publications

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“…The warm north polar lower mesosphere has cooled (as also suggested previously by Achterberg et al 2011) and now we find the decrease to be about 12 K at 50 • N (Figure 2(a)) and about 7 K at 30 • N (Figure 2(b)) at around 250-300 km in altitude, since the beginning of the Cassini mission. In the mid-stratosphere below 200 km, the northern polar region initially began cooling from 2007 up to 2009, while in 2010 a slight warming is observed again at both 50 • N and 30 • N.…”

Section: Temperature Evolution Of Titan's Stratosphere During the Cassupporting

confidence: 88%

“…Latitudinal variations in Titan's stratospheric thermal and chemical structure have been reported in the past from Cassini data acquired by the Composite Infrared Spectrometer (CIRS) (Flasar et al 2005;Teanby et al 2006;Coustenis et al 2007Coustenis et al , 2008Coustenis et al , 2010de Kok et al 2007;Teanby et al , 2008Teanby et al , 2009aVinatier et al 2007Vinatier et al , 2010Nixon et al 2008a;Achterberg et al 2008Achterberg et al , 2011. Here, we explore the thermal and chemical evolution discernible within the timeframe from 2006 to 2012, thus complementing and refining previous reports from earlier stages of the mission.…”

Section: Context and Observationsmentioning

confidence: 55%

“…Our list of molecules includes in particular the 13 CH 4 , 13 CH 3 D, 12 C 13 CH 2, and H 15 CN isotopologues which are essential in fitting the emission bands of methane, acetylene, and hydrogen cyanide and allow us to infer the 12 C/ 13 C and 14 N/ 15 N ratios. Furthermore, new oxygen and hydrocarbon isotopologues as detected by Jennings et al (2008) and Nixon et al (2008b) We first retrieve temperature profiles by the inversion of the observed ν 4 methane emission band at 1305 cm −1 in CIRS FP4 following the method described in Achterberg et al (2008Achterberg et al ( , 2011. We use the CH 4 vertical mixing ratio profile in the stratosphere as measured by the Huygens probe (Niemann et al 2010) and compatible with the CIRS inferences from FP1 (Flasar et al 2005), which yields 1.48% above the cold trap.…”

Section: Discussionmentioning

confidence: 99%

“…These changes at northern latitudes suggest a weakening of the descending branch of the middle atmosphere meridional circulation (Achterberg et al 2011), which implies less adiabatic heating and hence lower temperatures. Moreover, the changes in the circulation affect the distribution of aerosols (Vinatier et al 2012a), which in turn affect the thermal structure.…”

Section: Temperature Evolution Of Titan's Stratosphere During the Casmentioning

confidence: 99%

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THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THECASSINIMISSION

Bampasidis

Coustenis

Achterberg

et al. 2012

ApJ

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We have developed a line-by-line Atmospheric Radiative Transfer for Titan code that includes the most recent laboratory spectroscopic data and haze descriptions relative to Titan's stratosphere. We use this code to model Cassini Composite Infrared Spectrometer data taken during the numerous Titan flybys from 2006 to 2012 at surface-intercepting geometry in the 600-1500 cm −1 range for latitudes from 50 • S to 50 • N. We report variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE). We find indication for a weakening of the temperature gradient with warming of the stratosphere and cooling of the lower mesosphere. In addition, we infer precise concentrations for the trace gases and their main isotopologues and find that the chemical composition in Titan's stratosphere varies significantly with latitude during the 6 years investigated here, with increased mixing ratios toward the northern latitudes. In particular, we monitor and quantify the amplitude of a maximum enhancement of several gases observed at northern latitudes up to 50 • N around mid-2009, at the time of the NSE. We find that this rise is followed by a rapid decrease in chemical inventory in 2010 probably due to a weakening north polar vortex with reduced lateral mixing across the vortex boundary.

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Section: Temperature Evolution Of Titan's Stratosphere During the Cassupporting

confidence: 88%

Section: Context and Observationsmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 99%

Section: Temperature Evolution Of Titan's Stratosphere During the Casmentioning

confidence: 99%

See 2 more Smart Citations

THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THECASSINIMISSION

Bampasidis

Coustenis

Achterberg

et al. 2012

ApJ

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“…The predicted superrotation at equinox is centered at the equator near the upper boundary because angular momentum is carried upward near the equator in this season. Although such an upward shift of the jet core at equinox is confirmed by observations [Achterberg et al, 2011], the peak zonal wind ( 90 m s -1 ) (Figure 2b) is still much weaker than observed (up to 200 m s -1 ). Accordingly, the latitudinal temperature is greatly underestimated, especially near the winter/spring pole (Figure 2d).…”

Section: Representation Of the Wind-induced Equatorial Bulge In Gcmssupporting

confidence: 72%

Wind‐induced equatorial bulge in Venus and Titan general circulation models: Implication for the simulation of superrotation

Tokano

2013

Geophysical Research Letters

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[1] The centrifugal force associated with the superrotation in Venus' and Titan's middle atmosphere reduces the effective gravity and thereby modifies the shape of the geopotential surface, which manifests itself as an equatorial bulge. General circulation models (GCMs) based on the hydrostatic primitive equations cannot correctly represent this dynamics since the vertical component of the centrifugal force does not appear in the hydrostatic equation. Consequently, they are likely to underestimate the poleward pressure gradient force and superrotation in gradient wind balance. This effect can be accounted for in nonhydrostatic GCMs or in quasi-hydrostatic GCMs, in which the hydrostatic equation is supplemented by the vertical component of the centrifugal and Coriolis force and which do not make the shallow-atmosphere approximation. A quasi-hydrostatic GCM is shown to predict faster superrotation than a hydrostatic GCM run under otherwise identical conditions. Citation: Tokano, T. (2013), Wind-induced equatorial bulge in Venus and Titan general circulation models: Implication for the simulation of superrotation, Geophys. Res. Lett., 40,[4538][4539][4540][4541][4542][4543]

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What causes Mars' annular polar vortices?

Toigo

Waugh

Guzewich

2017

Geophysical Research Letters

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A distinctive feature of the Martian atmosphere is that the winter polar vortices exhibit annuli of high potential vorticity (PV) with a local minimum near the pole. These annuli are seen in observations, reanalyses, and free‐running general circulation model simulations of Mars, but are not generally a feature of Earth's polar vortices, where there is a monotonic increase in magnitude of PV with latitude. The creation and maintenance of the annular polar vortices on Mars are not well understood. Here we use simulations with a Martian general circulation model to the show that annular vortices are related to another distinctive, and possibly unique in the solar system, feature of the Martian atmosphere: the condensation of the predominant atmospheric gas species (CO2) in polar winter regions. The latent heat associated with CO2 condensation leads to destruction of PV in the polar lower atmosphere, inducing the formation of an annular PV structure.

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Temporal variations of Titan’s middle-atmospheric temperatures from 2004 to 2009 observed by Cassini/CIRS

Cited by 89 publications

References 42 publications

THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THECASSINIMISSION

THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THECASSINIMISSION

Wind‐induced equatorial bulge in Venus and Titan general circulation models: Implication for the simulation of superrotation

What causes Mars' annular polar vortices?

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