From Voyager-IRIS to Cassini-CIRS: Interannual Variability in Saturn's Stratosphere
Abstract
We present an intercomparison of Saturn's atmosphere from Voyager-IRIS observations in 1980 with Cassini-CIRS observations in 2009/2010. Over a Saturn year (∼29.5 years) has now passed since the Voyager flyby of Saturn in 1980/1981. Cassini observations in 2009/2010 and those from Voyager therefore capture Saturn in the same season (at approximately the vernal equinox, solar longitude, Ls~∼0°). Any differences in Saturn's stratospheric properties implied by a comparison of these two datasets will therefore highlight interannual variability. We retrieve temperature and stratospheric acetylene and ethane concentrations from Voyager 1-IRIS (FWHM = 4.3 cm-1) in 1980 and Cassini-CIRS 'FIRMAP' (FWHM = 15.5 cm-1) observations in 2009/2010. Preliminary results show the equator to be warmer by 7.3 ± 1.6 K at ∼2.1 mbar in 2009 than in 1980 implying a differing phase of the SSAO (Saturn's semi-annual oscillation). Ethane's meridional distribution at 2.1 mbar appears consistent between 1980 and 2009/2010. However, the concentrations of acetylene at the same altitude appear enhanced at ∼25°S and ∼25°N in 1980 when compared to 2009/2010. A global-circulation model shows cells of downwelling at these latitudes [3]: the richer concentrations of acetylene at these latitudes in 1980 suggests that there was stronger downwelling at this time than in 2009.
- Publication:
-
European Planetary Science Congress
- Pub Date:
- September 2013
- Bibcode:
- 2013EPSC....8...35S