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Physical State and Composition of Polar Stratospheric Clouds Inferred from Airborne Lidar Measurements During SESAME

Abstract : The airborne lidar LEANDRE was deployed from Kiruna (Sweden) in January1995, during Phase III of the Second European Stratospheric Arctic andMid-latitude Experiment (SESAME). Polar Stratospheric Clouds (PSC) weredetected on several flights. Four lidar retrievals, on two different days, arepresented together with the thermal history of air masses, derived from 5-daybackward trajectories calculated from the TOPCAT model, using ECMWF analyses.The first PSC case was observed at the synoptic scale and at a temperatureclose to the ice frost point, with no significant depolarization, suggestingthat particles were in the liquid phase, probably liquid ternaryH2SO4/HNO3/H2Osolution forming a Type 1b cloud. Locally, on the same day, a Type II PSC (icecloud) was detected above the Scandinavian Mountains and was related tomesoscale processes. On another day, the third lidar retrieval only showedbackground aerosols signature, whereas the last one was performed at the NATequilibrium temperature and its measured depolarization ratio was consistentwith few solid state Type Ia particles, probably composed of NAT. From thethermal histories, the different behaviour of the two Type I clouds isexplained in terms of cooling rates and compositional hysteresis, driven bytemperature.
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Submitted on : Tuesday, December 22, 2020 - 10:52:51 AM
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Christine David, Sophie Godin, Gérard Mégie, Y. Emery, C. Flesia. Physical State and Composition of Polar Stratospheric Clouds Inferred from Airborne Lidar Measurements During SESAME. Journal of Atmospheric Chemistry, Springer Verlag, 1997, 27, pp.1-16. ⟨10.1023/A:1005820407467⟩. ⟨insu-03085971⟩

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