Diurnal Variability in EMIRS Daytime Observations of Water Ice Clouds During Mars Aphelion?Season

Diurnal analyses of water ice cloud optical depths retrieved from thermal infrared spectra by the Emirates Mars Infrared Spectrometer showed changing abundance throughout Martian day. Observations began with start Mission science phase near beginning aphelion-season in Year 36 and included prominent aphelion belt (ACB) orographic clouds vicinity volcanoes. A midday minimum higher morning afternoon was typical for ACB, though considerable spatial variability this diurnal pattern. Clouds volcanoes reached a before local noon tended to increase afternoon. Comparisons against Laboratoire de Météorologie Dynamique global circulation model analogous patterns signal, which suggested tides topographic effects be predominant drivers ACB variability, while more localized circulations affected volcano clouds.