Abstract The present study used the observations from Mars Color Camera (MCC) onboard Mars Orbiter Mission, from the two instruments onboard Mars Reconnaissance Orbiter, i.e., Mars Climate Sounder (MCS) and Mars Color Imager (MARCI), for investigating the water ice cloud appearance over two Martian volcanos, Olympus Mons and Arsia Mons. Indeed, these regions offer an opportunity to explore the dynamical effects related to the orographic clouds and give an idea about their interactions with atmospheric transport. Also, the long-term MCS profile observations are much useful to emphasize the sub-seasonal, seasonal, and interannual variability of clouds at different altitudes. The MCC and MARCI images show a cloud patch over Olympus Mons within the aphelion and a thin cloud trails over Arsia Mons within the perihelion of Mars years. Night-time MCS observations suggest an appearance of thick low altitude clouds within 15 – 32 km height during LS = 35 – 150° and thin high-altitude clouds within 30 – 50 km height during LS = 225 – 315°. The profile observations over both the volcanic regions show that the atmospheric temperature variations more strongly control the water ice cloud distribution at lower altitudes during northern hemispheric spring and summer. In contrast, the high altitude thin clouds during southern hemispheric spring and summer are found to be more associated with the elevated dustiness and vertical advection of dust-laden mountain induced regional circulation, as suggested by MarsWRF simulated wind. The appearance of the consistent thick followed by thin clouds during aphelion and perihelion season shows a nearly constant cloud water content of ∼0.2 and ∼0.05 pr μm. The high or low magnitude of cloud water content could be distinguished from the peak water ice extinction within the column, as observed in the inter-annual variations. However, irrespective of low cloud water content during the second half of the year, the presence of high altitude thin clouds leads to an overall cloud vertical depth (≥ 30 km) higher (mostly visible during the night) than the first half of the year. Comparison of the nighttime appearance of thick clouds (centered at ∼20 km) during the first half and thin clouds (centered at ∼40 km) during the second half of the year over two volcanos indicates the suitable atmospheric conditions in the case of the Olympus Mons for the former type clouds and over Arsia Mons for the later. Also, the appearance of thick clouds mostly resembles the consistent and stable aphelion cloud cycle. In contrast, the thin high altitude clouds are more variable and influenced by the vertical advection during the perihelion season. Besides, these high altitude clouds drive the more prominent east-west asymmetry in the cloud abundance over the Arsia Mons region during the perihelion period.

中文翻译：

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使用 MOM 和 MRO 观测的奥林匹斯山和 Arsia Mons 上空水冰云的特征

摘要 本研究利用火星轨道飞行器上的火星彩色相机（MCC）的观测结果，利用火星勘测轨道飞行器上的两种仪器，即火星气候探测器（MCS）和火星彩色成像仪（MARCI），对水冰云进行调查。出现在两座火星火山，奥林匹斯山和阿尔西亚山。事实上，这些区域提供了一个机会来探索与地形云相关的动力效应，并提供关于它们与大气传输相互作用的想法。此外，长期 MCS 剖面观测对于强调不同高度云的次季节、季节和年际变化非常有用。MCC 和 MARCI 图像显示远日点内奥林匹斯山上空的云块和火星近日点内阿尔西亚山上空的薄云尾迹。夜间 MCS 观测表明，在 LS = 35 – 150° 期间，在 15 – 32 公里高度内出现厚的低空云，在 LS = 225 – 315° 期间，在 30 – 50 公里高度内出现薄高空云。两个火山区的剖面观测表明，北半球春季和夏季，大气温度变化对低海拔水冰云分布的控制更强。相比之下，正如MarsWRF模拟风所表明的那样，南半球春季和夏季的高空薄云被发现更多地与满载灰尘的山区引起的区域环流的高尘和垂直平流有关。在远日点和近日点季节出现一致的厚云和薄云，表明云水含量几乎恒定为~0.2 和~0。05 微米。正如在年际变化中观察到的那样，可以将云水含量的高低与柱内水冰消光的峰值区分开来。然而，尽管下半年云水含量低，但高空薄云的存在导致整体云垂直深度（≥30公里）比上半年高（主要在夜间可见） . 两座火山在上半年的浓云（以~20公里为中心）和下半年的薄云（以~40公里为中心）夜间出现的比较表明奥林匹斯山的适宜大气条件前者类型云为 Mons，后者为 Arsia Mons。还，厚云的出现大多类似于一致且稳定的远日点云周期。相比之下，薄的高空云变化更大，受近日季节垂直平流的影响。此外，这些高海拔云在近日点期间驱动了Arsia Mons地区云丰度的更显着的东西不对称性。