Seasonal evolution of Titan's stratosphere during the Cassini mission.
Seasonal evolution of Titan's stratosphere during the Cassini mission.
复制标题
卡西尼号任务期间泰坦平流层的季节性演变。
DOI：
10.1029/2018gl081401
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发表时间：
2019
影响因子：
5.2
通讯作者：
Teanby NA
中科院分区：
文献类型：
--
作者：
Teanby NA
土卫六的平流层呈现出显著的季节性变化，包括极涡的分裂和形成。在这里，我们提出了卡西尼号复合红外光谱仪的中红外测绘观测的第一个分析，涵盖了整个使命（Ls=293-93°，2004-2017）-中北方冬季到北方夏至。北极冬季涡旋在春分后持续很长时间，在Ls <$60 °左右开始分裂，到Ls <$90 °时完全消散。缺乏向低纬度扩散的浓缩极地空气表明大尺度环流变化和光化学控制涡旋破裂期间的化学演变。南极涡旋在春分后不久就开始形成，到60° L时，它比北方仲冬涡旋更富含微量气体，温度也低了20 K左右。这表明，初冬和中冬涡旋分别由不同的过程控制-辐射冷却和沉降诱导的绝热加热。到使命结束时（Ls=93°），南极的条件接近在Ls =293°时在北极观察到的条件，这意味着土卫六涡旋的季节对称性。
Titan's stratosphere exhibits significant seasonal changes, including breakup and formation of polar vortices. Here we present the first analysis of midinfrared mapping observations from Cassini's Composite InfraRed Spectrometer to cover the entire mission (Ls=293–93°, 2004–2017)—midnorthern winter to northern summer solstice. The north polar winter vortex persisted well after equinox, starting breakup aroundLs∼60° and fully dissipating byLs∼90°. Absence of enriched polar air spreading to lower latitudes suggests large‐scale circulation changes and photochemistry control chemical evolution during vortex breakup. South polar vortex formation commenced soon after equinox and byLs∼60° was more enriched in trace gases than the northern middle‐winter vortex and had temperatures ∼20 K colder. This suggests that early‐winter and middle‐winter vortices are dominated by different processes—radiative cooling and subsidence‐induced adiabatic heating respectively. By the end of the mission (Ls=93°) south polar conditions were approaching those observed in the north atLs=293°, implying seasonal symmetry in Titan's vortices.