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Martian water ice clouds during the 2018 global dust storm as observed by the ACS-MIR channel onboard the Trace Gas Orbiter

Abstract : The Atmospheric Chemistry Suite (ACS) instrument onboard the ExoMars Trace Gas Orbiter (TGO) ESA-Roscosmos mission began science operations in March 2018. ACS Mid InfraRed (MIR) channel notably provides solar occultation observations of the martian atmosphere in the 2.3 – 4.2 μm spectral range. Here we use these observations to characterize water ice clouds before and during the MY 34 Global Dust Storm (GDS). We developed a method to detect water ice clouds with mean particle size ≤ 2 μm, and applied it to observations gathered between Ls = 165◦ and Ls = 243◦. We observe a shift in water ice clouds maximum altitudes from about 60 km before the GDS to above 90 km during the storm. These very high altitude, small-sized (reff ≤ 0.3 μm) water ice clouds are more frequent during MY34 compared to non- GDS years at the same season. Particle size frequently decreases with altitude, both locally within a given profile and globally in the whole dataset. We observe that the maximum altitude at which a given size is observed can increase during the GDS by several tens of km for certain sizes. We notably notice some large water ice particles (reff ≥ 1.5 μm) at surprisingly high altitudes during the GDS (50 – 70 km). These results suggest that GDS can significantly impact the formation and properties of high altitude water ice clouds as compared to the usual perihelion dust activity.
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https://hal-insu.archives-ouvertes.fr/insu-02492315
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Submitted on : Wednesday, February 26, 2020 - 6:54:18 PM
Last modification on : Tuesday, August 4, 2020 - 7:04:02 PM

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Aurélien Stcherbinine, M. Vincendon, Franck Montmessin, M. J. Wolff, Oleg Korablev, et al.. Martian water ice clouds during the 2018 global dust storm as observed by the ACS-MIR channel onboard the Trace Gas Orbiter. Journal of Geophysical Research. Planets, Wiley-Blackwell, 2020, 125 (3), pp.e2019JE006300. ⟨10.1029/2019JE006300⟩. ⟨insu-02492315⟩

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