| Autor: |
Teanby NA; School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK., Sylvestre M; School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK., Sharkey J; School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK., Nixon CA; Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA., Vinatier S; LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France., Irwin PGJ; Atmospheric, Oceanic & Planetary Physics, Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU. UK. |
| Abstrakt: |
Titan's stratosphere exhibits significant seasonal changes, including break-up and formation of polar vortices. Here we present the first analysis of mid-infrared mapping observations from Cassini's Composite InfraRed Spectrometer (CIRS) to cover the entire mission (L s =293-93°, 2004-2017) - mid-northern winter to northern summer solstice. The north-polar winter vortex persisted well after equinox, starting break-up around L s ∼60°, and fully dissipating by L s ∼90°. Absence of enriched polar air spreading to lower latitudes suggests large-scale circulation changes and photochemistry control chemical evolution during vortex break-up. South-polar vortex formation commenced soon after equinox and by L s ∼60° was more enriched in trace gases than the northern mid-winter vortex and had temperatures ∼20 K colder. This suggests early-winter and mid-winter vortices are dominated by different processes - radiative cooling and subsidence-induced adiabatic heating respectively. By the end of the mission (L s =93°) south-polar conditions were approaching those observed in the north at L s =293°, implying seasonal symmetry in Titan's vortices. |
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