火星阿尔西亚山火山上空极度拉长的云：II. 中尺度模拟
An Extremely Elongated Cloud over Arsia Mons Volcano on Mars: II. Mesoscale modeling
AI总结：
本文利用LMD中尺度模式模拟火星阿尔西亚山拉长云，揭示西坡下坡风暴和水跃触发强上升气流导致高空降温，成功再现云头部日循环但未能模拟尾部扩展和微物理特征。
摘要：
在之前的工作中（Hernández-Bernal et al. 2021），我们对阿尔西亚山拉长云（AMEC）进行了观测分析。该云因其惊人的规模和形状、快速的动力学特征以及出现在火星沙尘季节而引人注目。观测表明，其形态可分为头部和尾部：头部位于火山西坡，直径约120公里；尾部向西延伸，长度超过1000公里，使AMEC成为迄今在太阳系中观测到的最长地形云。在本工作中，我们运行LMD（Laboratoire de Météorologie Dynamique，动力气象实验室）中尺度模式，以深入了解AMEC的物理机制。我们注意到，该云在地方时和季节性上与阿尔西亚山顶最快的风相吻合。西坡的下坡风暴之后出现类似水跃的现象，触发强烈的垂直上升气流，该气流在大气中向上传播，导致40-50公里高度处温度下降达30K，在空间和时间上与观测到的AMEC头部一致。然而，该模式未能再现此云的微物理过程：光学厚度过低，且模式中未出现尾部的扩展。模式正确捕捉到了云头部的观测日循环。本工作提出了新的问题，将为未来对AMEC的观测提供指导。
英文摘要：
In a previous work (Hernández-Bernal et al. 2021) we performed an observational analysis of the Arsia Mons Elongated Cloud (AMEC), which stands out due to its impressive size and shape, quick dynamics, and the fact that it happens during the martian dusty season. Observations show that its morphology can be split in a head, on the western slope of the volcano of around 120 km in diameter; and a tail, that expands to the west reaching more than 1000 km in length, making the AMEC the longest orographic cloud observed so far in the solar system. In this work we run the LMD (Laboratoire de Météorologie Dynamique) Mesoscale Model to gain insight into the physics of the AMEC. We note that it is coincident in terms of local time and seasonality with the fastest winds on the summit of Arsia Mons. A downslope windstorm on the western slope is followed by a hydraulic-like jump triggering a strong vertical updraft that propagates upwards in the atmosphere, causing a drop in temperatures of down to 30K at 40-50 km in altitude, spatially and temporarily coincident with the observed head of the AMEC. However the model does not reproduce the microphysics of this cloud: the optical depth is too low and the expansion of the tail does not happen in the model. The observed diurnal cycle is correctly captured by the model for the head of the cloud. This work raises new questions that will guide future observations of the AMEC.
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