摘要：Aims.We study the seasonal evolution of Titan’s lower stratosphere (around 15 mbar) in order to better understand the atmospheric dynamics and chemistry in this part of the atmosphere.Methods.We analysedCassini/CIRS far-IR observations from 2006 to 2016 in order to measure the seasonal variations of three photochemical by-products:C4H2,C3H4, andC2N2.Results.We show that the abundances of these three gases have evolved significantly at northern and southern high latitudes since 2006. We measure a sudden and steep increase of the volume mixing ratios ofC4H2,C3H4, andC2N2at the south pole from 2012 to 2013, whereas the abundances of these gases remained approximately constant at the north pole over the same period. At northern mid-latitudes,C2N2andC4H2abundances decrease after 2012 whileC3H4abundances stay constant. The comparison of these volume mixing ratio variations with the predictions of photochemical and dynamical models provides constraints on the seasonal evolution of atmospheric circulation and chemical processes at play.
关键词：enplanets and satellites: atmospheresmethods: data analysis
