Mechanisms of Banner Cloud Formation
Mechanisms of Banner Cloud Formation
复制标题
横幅云的形成机制
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
V. Wirth
中科院分区：
文献类型：
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作者：
Matthias Voigt;V. Wirth
摘要 旗云是陡峭山脉或尖锐山脊背风处的云。先前假设它们的形成是由于三种不同的机制：（i）背风涡旋（具有水平轴）中的垂直隆起，（ii）沿准水平轨迹的绝热膨胀（所谓的伯努利效应），以及（iii）混合云（即通过两个不饱和气团的混合而凝结）。在目前的工作中，通过大涡流对这些假设进行了测试和定量评估模拟。选择模型设置来代表横幅云形成的理想但典型的条件。在这种设置中，背风涡机制显然是横幅云形成的主要机制。一个重要方面是拉格朗日垂直隆升中明显的迎风-背风不对称性，在山的直接背风处有大量正值；这使得背风区域能够从更靠近地表的地方汲取潮湿的空气......
AbstractBanner clouds are clouds in the lee of steep mountains or sharp ridges. Their formation has previously been hypothesized as due to three different mechanisms: (i) vertical uplift in a lee vortex (which has a horizontal axis), (ii) adiabatic expansion along quasi-horizontal trajectories (the so-called Bernoulli effect), and (iii) a mixing cloud (i.e., condensation through mixing of two unsaturated air masses).In the present work, these hypotheses are tested and quantitatively evaluated against each other by means of large-eddy simulation. The model setup is chosen such as to represent idealized but prototypical conditions for banner cloud formation. In this setup the lee-vortex mechanism is clearly the dominant mechanism for banner cloud formation. An essential aspect is the pronounced windward–leeward asymmetry in the Lagrangian vertical uplift with a plume of large positive values in the immediate lee of the mountain; this allows the region in the lee to tap moister air from closer to the surface...
影响因子：
4.3
作者：
D. Reinert;V. Wirth
通讯作者：
D. Reinert;V. Wirth