Seasonal change on Saturn from Cassini/CIRS observations, 2004–2009

Fletcher, Leigh N.; Achterberg, R. K.; Greathouse, Thomas; Orton, Glenn S.; Conrath, B. J.; Simon-Miller, A. A.; Teanby, N. A.; Guerlet, Sandrine; Irwin, Patrick; Flasar, F. M.

doi:10.1016/j.icarus.2010.01.022

Cited by 73 publications

(108 citation statements)

References 45 publications

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“…Figure 10 shows the haze distribution overlaid upon the CIRS temperature field (Fletcher et al, 2010). Also marked are the pressures at which the environmental lapse rate reaches dry adiabatic (around 500 mbar) and changes sign (around 100 mbar).…”

Section: Meridional Resultsmentioning

confidence: 99%

“…The stratospheric and tropospheric haze distribution as a function of latitude superimposed upon a temperature field provided by Fletcher et al (2010). The dashed line at ~100 mbar marks where the temperature lapse rate changes sign, and the dashed-dotted line at ~400 mbar marks where the lapse rate approaches dry adiabatic (~0.715 K/km).…”

Section: Meridional Resultsmentioning

confidence: 99%

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Saturn’s cloud structure inferred from Cassini ISS

Roman

Banfield

Gierasch

2013

Icarus

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Using high-resolution Cassini ISS images with wavelengths ranging from the ultraviolet to the near infrared, we have retrieved Saturn's atmospheric aerosol structure and properties for a broad range of latitudes in the southern hemisphere. The observations are consistent with two distinct layers of haze. Each layer is characterized by a vertical location, an optical depth, and a mean particle size, all of which vary with latitude. The tropospheric haze is optically thickest and extends to the greatest heights (~40 mbar) over the equator; its top surface is at significantly greater depths (~150 mbar ) at mid-latitudes. The height of the haze correlates well with position of the tropopause as indicated by the temperature field. Beneath this haze, we find a scattered denser cloud responsible for small-scale contrasts at an average depth of 1.75 ± 0.4 bar, with some features deeper than 2.5 bar.iii BIOGRAPHICAL SKETCHMichael Roman transferred into Cornell University in 2004 as a junior in the field of Atmospheric Sciences, after having studied at a small community college. As an undergraduate, he became involved in research as a student research assistant, organizing and processing image data from the Galileo mission. The project combined two of his of long-lived interest-meteorology and astronomy-and encouraged him to pursue further research experience.

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Section: Meridional Resultsmentioning

confidence: 99%

Section: Meridional Resultsmentioning

confidence: 99%

Saturn’s cloud structure inferred from Cassini ISS

Roman

Banfield

Gierasch

2013

Icarus

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“…An a priori temperature profile was estimated as a mean of Cassini/CIRS T (p) profiles between ±45 • latitude from Cassini's prime mission (sensitive to the 1-800 mbar range, Fletcher et al 2010). The PH 3 profile was initially set to the CIRS-derived mole fraction of 6.4 ppm at p > 0.55 bar, decreasing due to photolysis at lower pressures with a fractional scale height of 0.27 (the ratio of the PH 3 scale height to the scale height of the bulk atmosphere, Fletcher et al 2009a).…”

Section: Saturn Continuum Modelling: Temperatures Ph 3 and Nhmentioning

confidence: 99%

Sub-millimetre spectroscopy of Saturn’s trace gases fromHerschel/SPIRE

Fletcher

Swinyard

Salji

et al. 2012

A&A

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Aims. We provide an extensive new sub-millimetre survey of the trace gas composition of Saturn's atmosphere using the broad spectral range (15-51 cm −1 ) and high spectral resolution (0.048 cm −1 ) offered by Fourier transform spectroscopy by the Herschel/SPIRE instrument (Spectral and Photometric Imaging REceiver). Observations were acquired in June 2010, shortly after equinox, with negligible contribution from Saturn's ring emission. Methods. Tropospheric temperatures and the vertical distributions of phosphine and ammonia are derived using an optimal estimation retrieval algorithm to reproduce the sub-millimetre data. The abundance of methane, water and upper limits on a range of different species are estimated using a line-by-line forward model. Results. Saturn's disc-averaged temperature profile is found to be quasi-isothermal between 60 and 300 mbar, with uncertainties of 7 K due to the absolute calibration of SPIRE. Modelling of PH 3 rotational lines confirms the vertical profile derived in previous studies and shows that negligible PH 3 is present above the 10-to 20-mbar level. The upper tropospheric abundance of NH 3 appears to follow a vapour pressure distribution throughout the region of sensitivity in the SPIRE data, but the degree of saturation is highly uncertain. The tropospheric CH 4 abundance and Saturn's bulk C/H ratio are consistent with Cassini studies. We improve the upper limits on several species (H 2 S, HCN, HCP and HI); provide the first observational constraints on others (SO 2 , CS, methanol, formaldehyde, CH 3 Cl); and confirm previous upper limits on HF, HCl and HBr. Stratospheric emission from H 2 O is suggested at 36.6 and 38.8 cm −1 with a 1σ significance level, and these lines are used to derive mole fractions and column abundances consistent with ISO and SWAS estimations a decade earlier.

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“…The 2010 event occurred at a much earlier springtime season within the same westward jet as the 1903 event [5][6][7][8][9] , ponting towards seasonal insolation as their triggering mechanism. This is puzzling since the solar radiation penetration in Saturn s atmosphere 24 and thermal infrared measurements 21,25 , indicate that seasonal temperature changes occur only above ∼ 500 mbar altitude, much higher than the 10-12 bar level for the storm source [9][10] . The zonal wind profile at 0. v uPmPP = is a non-dimensional vertical amplitude factor.…”

mentioning

confidence: 99%