Seasonal and interannual variability in Saturn's stratosphere
<p>The stratosphere of Saturn is highly variable. With an axial tilt of 26.7°, Saturn experiences seasons like Earth and is currently approaching northern summer solstice in 2017. In addition to general seasonal change, previous studies have highlighted that Saturn's stratosphere is host...
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| Format: | Thesis |
| Language: | English |
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2014
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| _version_ | 1826315802670792704 |
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| author | Sinclair, JA |
| author2 | Irwin, P |
| author_facet | Irwin, P Sinclair, JA |
| author_sort | Sinclair, JA |
| collection | OXFORD |
| description | <p>The stratosphere of Saturn is highly variable. With an axial tilt of 26.7°, Saturn experiences seasons like Earth and is currently approaching northern summer solstice in 2017. In addition to general seasonal change, previous studies have highlighted that Saturn's stratosphere is host to a range of dynamical phenomena. These processes have an observable effect on the vertical temperature profile and stratospheric concentrations of acetylene (C<sub>2</sub>H<sub>2</sub>) and ethane (C<sub>2</sub>H<sub>6</sub>), which may be determined or <em>retrieved</em> from thermal infrared observations of Saturn. This thesis presents an analysis of observations of Saturn acquired by Voyager's IRIS (Infrared Interferometer Spectrometer, 180 - 2500 <sup>cm-1</sup>, Hanel et al.,[1980]) instrument in 1980, Cassini's CIRS (Composite Infrared Spectrometer, 10 - 1400 <sup>cm-1</sup>, Flasar et al.,[2004]) instrument from 2005 to 2012 and the Celeste spectrometer (400 - 2000 <sup>cm-1</sup>, Moran et al.,[2007]) on NASA's IRTF (Infrared Telescope Facility) in 2012 in order to track seasonal and interannual changes in Saturn's stratosphere.</p> The concentrations of C<sub>2</sub>H<sub>2</sub> and C<sub>2</sub>H<sub>6</sub> were seen to decrease at 15°S and increase at 25°N from 2005 to 2009/2010. These changes at 15°S and 25°N respectively indicate upward and downward branches associated with cross-equatorial <em>seasonally-reversing Hadley circulation</em> that has been predicted by a general circulation model [Friedson and Moses, 2012]. Strong cooling of up to 17 K at high-southern latitudes from 2005 to 2010 suggests an autumnal weakening of a vortex that appears to form at the pole of the summer hemisphere [Fletcher et al., 2008]. The emergence of a similar northern polar vortex as northern summer solstice approaches was yet to be observed in 2012. Interannual differences in the equatorial temperature structure between 1980 and 2009/2010 suggest Saturn's semiannual oscillation (or SSAO, Fouchet et al. [2008]; Orton et al. [2008]) has been captured in a different phase from one <em>year</em> to the next. This is puzzling since the oscillation would be expected to have undergone two cycles assuming its period is half a Saturn year (14.7 years). This contrast is suggestive that the period of the SSAO is more quasisemiannual. |
| first_indexed | 2024-03-07T07:47:58Z |
| format | Thesis |
| id | oxford-uuid:1ae2289b-a615-4d16-8f01-b13ea10f3bbe |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:32:53Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:1ae2289b-a615-4d16-8f01-b13ea10f3bbe2024-12-01T16:00:59ZSeasonal and interannual variability in Saturn's stratosphereThesishttp://purl.org/coar/resource_type/c_db06uuid:1ae2289b-a615-4d16-8f01-b13ea10f3bbeAtmospheric,Oceanic,and Planetary physicsEnglishOxford University Research Archive - Valet2014Sinclair, JAIrwin, P<p>The stratosphere of Saturn is highly variable. With an axial tilt of 26.7°, Saturn experiences seasons like Earth and is currently approaching northern summer solstice in 2017. In addition to general seasonal change, previous studies have highlighted that Saturn's stratosphere is host to a range of dynamical phenomena. These processes have an observable effect on the vertical temperature profile and stratospheric concentrations of acetylene (C<sub>2</sub>H<sub>2</sub>) and ethane (C<sub>2</sub>H<sub>6</sub>), which may be determined or <em>retrieved</em> from thermal infrared observations of Saturn. This thesis presents an analysis of observations of Saturn acquired by Voyager's IRIS (Infrared Interferometer Spectrometer, 180 - 2500 <sup>cm-1</sup>, Hanel et al.,[1980]) instrument in 1980, Cassini's CIRS (Composite Infrared Spectrometer, 10 - 1400 <sup>cm-1</sup>, Flasar et al.,[2004]) instrument from 2005 to 2012 and the Celeste spectrometer (400 - 2000 <sup>cm-1</sup>, Moran et al.,[2007]) on NASA's IRTF (Infrared Telescope Facility) in 2012 in order to track seasonal and interannual changes in Saturn's stratosphere.</p> The concentrations of C<sub>2</sub>H<sub>2</sub> and C<sub>2</sub>H<sub>6</sub> were seen to decrease at 15°S and increase at 25°N from 2005 to 2009/2010. These changes at 15°S and 25°N respectively indicate upward and downward branches associated with cross-equatorial <em>seasonally-reversing Hadley circulation</em> that has been predicted by a general circulation model [Friedson and Moses, 2012]. Strong cooling of up to 17 K at high-southern latitudes from 2005 to 2010 suggests an autumnal weakening of a vortex that appears to form at the pole of the summer hemisphere [Fletcher et al., 2008]. The emergence of a similar northern polar vortex as northern summer solstice approaches was yet to be observed in 2012. Interannual differences in the equatorial temperature structure between 1980 and 2009/2010 suggest Saturn's semiannual oscillation (or SSAO, Fouchet et al. [2008]; Orton et al. [2008]) has been captured in a different phase from one <em>year</em> to the next. This is puzzling since the oscillation would be expected to have undergone two cycles assuming its period is half a Saturn year (14.7 years). This contrast is suggestive that the period of the SSAO is more quasisemiannual. |
| spellingShingle | Atmospheric,Oceanic,and Planetary physics Sinclair, JA Seasonal and interannual variability in Saturn's stratosphere |
| title | Seasonal and interannual variability in Saturn's stratosphere |
| title_full | Seasonal and interannual variability in Saturn's stratosphere |
| title_fullStr | Seasonal and interannual variability in Saturn's stratosphere |
| title_full_unstemmed | Seasonal and interannual variability in Saturn's stratosphere |
| title_short | Seasonal and interannual variability in Saturn's stratosphere |
| title_sort | seasonal and interannual variability in saturn s stratosphere |
| topic | Atmospheric,Oceanic,and Planetary physics |
| work_keys_str_mv | AT sinclairja seasonalandinterannualvariabilityinsaturnsstratosphere |