A Numerical Study of the 6 May 2012 Tsukuba City Supercell Tornado. Part II: Mechanisms of Tornadogenesis
A Numerical Study of the 6 May 2012 Tsukuba City Supercell Tornado. Part II: Mechanisms of Tornadogenesis
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DOI：
10.1175/mwr-d-15-0122.1
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发表时间：
2016-08
影响因子：
3.2
通讯作者：
Wataru Mashiko
中科院分区：
文献类型：
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作者：
Wataru Mashiko
第一部分利用水平网格间距为50m的高分辨率数值模拟结果，研究了2012年5月6日日本筑波超级单体中低空中气旋的涡度来源。在第二部分中，分析扩展到龙卷风发生的机制。龙卷风是在后侧下沉气流(RFD)外流涌出的前沿产生的。后向轨迹和涡线分析表明，RFD外流涌动是龙卷风发生的触发因子，强RFD外流区周围的水平涡度被龙卷风吞噬。为了确定龙卷风的涡量来源，研究了龙卷风周围物质环流的演变。在龙卷风发生前约10分钟，由于水流星中心下降时，由于水流星尖端的斜压性(下称“水钩回波”)，环流从负值迅速增加。安娜。
AbstractIn Part I, the vorticity sources of midlevel and low-level mesocyclones in the 6 May 2012 Tsukuba City, Japan, tornadic supercell were investigated by using high-resolution simulation results with a 50-m horizontal grid spacing. In Part II, the analyses are extended to the mechanisms of tornadogenesis. The tornado was generated at the leading edge of a rear-flank downdraft (RFD) outflow surge. Backward-trajectory and vortex line analyses revealed that the RFD outflow surge was a triggering factor for tornadogenesis and that horizontal vorticity around the strong RFD outflow region was ingested into the tornado. To identify the vorticity source of the tornado, the evolution of circulation along a material circuit surrounding the tornado was investigated. Owing to baroclinity at the tip of a hook-shaped distribution of hydrometeors (hereafter hook echo), the circulation increased rapidly from a negative value when the core of the hydrometeors was descending, about 10 min prior to tornadogenesis. Ana...