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

中文翻译：

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火星远日点季节水冰云的 EMIRS 日间观测的日变化

阿联酋火星红外光谱仪从热红外光谱中检索到的水冰云光学深度的昼夜分析显示，整个火星日云量都在变化。观测始于 36 年火星远日点季节开始附近的阿联酋火星任务科学阶段的开始，包括突出的远日点云带 (ACB) 和火山附近的地形云。上午和下午光学深度较高的中午最小值是 ACB 的典型特征，尽管这种昼夜模式具有相当大的空间变异性。火山附近的云在当地中午前达到最低值，并在整个下午趋于增加。与动态气象实验室的比较全球环流模型在昼夜信号中显示出类似的空间模式，这表明热潮汐和地形效应是 ACB 变化的主要驱动因素，而更局部的环流影响火山云。