High-resolution mapping of Martian water ice clouds using Mars Express OMEGA observations - Derivation of the diurnal cloud life cycle

Andre Szantai 1 Joachim Audouard 2 Jean-Baptiste Madeleine 1 François Forget 1 Alizée Pottier Ehouarn Millour 1 Brigitte Gondet 3 Yves Langevin 3 Jean-Pierre Bibring 3
1 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
2 IMPEC - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
3 IAS - Institut d'astrophysique spatiale
Abstract : The mapping in space and time of water ice clouds can help to explain the Martian water cycle and atmospheric circulation. For this purpose, an ice cloud index (ICI) corresponding to the depth of a water ice absorption band at 3.4 microns is derived from a series of OMEGA images (spectels) covering 5 Martian years. The ICI values for the corresponding pixels are then binned on a high-resolution regular grid (1° longitude x 1° latitude x 5° Ls x 1 h local time) and averaged. Inside each bin, the cloud cover is calculated by dividing the number of pixels considered as cloudy (after comparison to a threshold) to the number of all (valid) pixelsWe compare the maps of clouds obtained around local time 14:00 with collocated TES cloud observations (which were only obtained around this time of the day). A good agreement is found.Averaged ICI compared to the water ice column variable from the Martian Climate Database (MCD) show a correct correlation (~0.5) , which increases when values limited to the tropics only are compared.The number of gridpoints containing ICI values is small ( ~1%), but by taking several neighbor gridpoints and over longer periods, we can observe a cloud life cycle during daytime. An example in the the tropics, around the northern summer solstice, shows a decrease of cloudiness in the morning followed by an increase in the afternoon.
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https://hal-insu.archives-ouvertes.fr/insu-01422002
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Submitted on : Friday, December 23, 2016 - 1:34:33 PM
Last modification on : Wednesday, May 15, 2019 - 3:41:30 AM

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Andre Szantai, Joachim Audouard, Jean-Baptiste Madeleine, François Forget, Alizée Pottier, et al.. High-resolution mapping of Martian water ice clouds using Mars Express OMEGA observations - Derivation of the diurnal cloud life cycle. DPS 48 / EPSC 11 (Division for Planetary Sciences and the European Planetary Science Congress), Oct 2016, Pasadena, United States. pp.id.409.02. ⟨insu-01422002⟩

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