Large Eddy Simulation of Dust Devils in a Diurnally-Evolving Convective Mixed Layer
Large Eddy Simulation of Dust Devils in a Diurnally-Evolving Convective Mixed Layer
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DOI：
10.2151/jmsj.2010-105
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发表时间：
2010-02
影响因子：
3.1
通讯作者：
J. Ito;R. Tanaka;H. Niino;M. Nakanishi
中科院分区：
文献类型：
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作者：
J. Ito;R. Tanaka;H. Niino;M. Nakanishi
用大涡模拟方法研究了日演变对流混合层中沙尘暴的形成。结果表明，较弱的总风和较强的地面热通量有利于沙尘暴的形成，其中胞状对流占优势，而滚流对流占优势。模拟结果表明，当总风较弱时，对流混合层的最大垂直涡度是w*的单调递增函数，其中w*是对流混合层的对流速度尺度。因此，沙尘暴最多发生在下午早些时候，此时热通量大，对流混合层发展到一个显著的高度。模拟的尘暴被发现具有与观测到的更大的尘暴相当的水平长度尺度。它们要么有单细胞结构，要么有两细胞结构。其中一些细胞最初具有单细胞结构，但后来演变为两细胞结构。
Formation of dust devils in diurnally-evolving convective mixed layers is studied by means of a large eddy simulation. It is found that a weaker general wind and a stronger surface heat flux for which cellular convection rather than roll convection prevails are favorable for the formation of dust devils. The simulation results show that when the general wind is weak, the maximum vertical vorticity in the convective mixed layer is a monotonically increasing function of w * , where w * is the convective velocity scale for a convective mixed layer. Therefore, dust devils occur most frequently in the early afternoon when the heat flux is large and the convective mixed layer grows to a significant height. The simulated dust devils are found to have a horizontal length scale comparable with observed larger dust devils. They have either one-celled or two-celled structure. Some of them have a one-celled structure initially, but later evolve into a two-celled structure.