Characterising Saturn's vertical temperature structure from Cassini/CIRS

Thermal infrared spectra of Saturn from 10-1400 cm(-1) at 15 cm(-1) spectral resolution and a spatial resolution of 1 degrees-2 degrees latitude have been obtained by the Cassini Composite Infrared Spectrometer [Flasar, F.M., and 44 colleagues, 2004. Space Sci. Rev. 115, 169-297]. Many thousands of...

Full description

Bibliographic Details
Published in:Icarus
Main Authors: Fletcher, L. N., Irwin, P. G. J., Teanby, N. A., Orton, G. S., Parrish, P. D., de Kok, R., Howett, C., Calcutt, S. B., Bowles, N., Taylor, F. W.
Format: Article in Journal/Newspaper
Language:English
Published: 2007
Subjects:
CLOUD STRUCTURE
HUBBLE-SPACE-TELESCOPE
structure
EQUATORIAL REGION
VOYAGER INFRARED MEASUREMENTS
ROTOTRANSLATIONAL ABSORPTION-SPECTRA
PARA-HYDROGEN FRACTION
UPPER TROPOSPHERE
OUTER PLANETS
Saturn
HELIUM ABUNDANCE
THERMAL STRUCTURE
atmospheres
composition
Hubble
Maguire
North Pole
South Pole
South pole
Online Access:https://hdl.handle.net/1983/249108b0-5d5e-4a4c-be28-a548a77bd055
https://research-information.bris.ac.uk/en/publications/249108b0-5d5e-4a4c-be28-a548a77bd055
https://doi.org/10.1016/j.icarus.2007.02.006
Description
Summary:Thermal infrared spectra of Saturn from 10-1400 cm(-1) at 15 cm(-1) spectral resolution and a spatial resolution of 1 degrees-2 degrees latitude have been obtained by the Cassini Composite Infrared Spectrometer [Flasar, F.M., and 44 colleagues, 2004. Space Sci. Rev. 115, 169-297]. Many thousands of spectra, acquired over eighteen-months of observations, are analysed using an optimal estimation retrieval code [Irwin, P.G.J., Parrish, P., Fouchet, T., Calcutt, S.B., Taylor, F.W., Simon-Miller, A.A., Nixon, C.A., 2004. Icarus 172, 37-49] to retrieve the temperature structure and para-hydrogen distribution over Saturn's northern (winter) and Southern (summer) hemispheres. The vertical temperature structure is analysed in detail to study seasonal asymmetries in the tropopause height (65-90 mbar), the location of the radiative-comective boundary (350-500 mbar), and the variation with latitude of a temperature knee (between 150 and 300 mbar) which was first observed in inversions of Voyager/IRIS spectra [Hanel, R., and 15 colleagues, 1981. Science 212, 192-200; Hanel, R., Conrath, B., Flasar, F.M., Kunde, V., Maguire, W., Pearl, J.C., Pirraglia, J., Samuelson, R., Cruikshank, D.P., Gautier, D., Gierasch, P.J., Horn, L., Ponnamperuma, C., 1982. Science 215, 544-548]. Uncertainties due to both the modelling of spectral absorptions (collision-induced absorption coefficients, tropospheric hazes, helium abundance) and the nature of our retrieval algorithm are quantified. Temperatures in the stratosphere near 1 mbar show a 25-30 K temperature difference between the north pole and south pole. This asymmetry becomes less pronounced with depth as the radiative time constant for the atmospheric response increases at deeper pressure levels. Hemispherically-symmetric small-scale temperature structures associated with zonal winds are superimposed onto the temperature asymmetry for pressures greater than 100 mbar. The para-hydro.-en fraction in the 100-400 mbar range is greater than equilibrium predictions for the southern ...

Similar Items