Effects of the Low-Level Wind Profile on Outflow Position and Near-Surface Vertical Vorticity in Simulated Supercell Thunderstorms
Effects of the Low-Level Wind Profile on Outflow Position and Near-Surface Vertical Vorticity in Simulated Supercell Thunderstorms
复制标题
模拟超级单体雷暴中低空风廓线对流出位置和近地表垂直涡度的影响
DOI：
10.1175/jas-d-17-0174.1
复制
发表时间：
2018
影响因子：
3.1
通讯作者：
Epifanio, Craig C.
中科院分区：
文献类型：
--
作者：
Guarriello, Felicia;Nowotarski, Christopher J.;Epifanio, Craig C.
利用理想数值模式模拟超级单体雷暴，分析环境低层风廓线的改变对近地面旋转的影响。具体地说，在几组实验中修正了低层垂直风切变的方向、大小和深度，并与规定层没有垂直风切变的控制模拟进行了比较。模拟超级单体的整体形态对低层风廓线的变化非常敏感。此外，最大近地面垂直涡度随着低层风廓线的改变而变化。结果表明，这主要是负浮力流出的有利动力强迫叠加在近地面环流最大值上的程度的结果。东风切变和较弱的风暴相对风在阵风锋深度上的模拟，与其他涡状图形状相比，促进了向前涌动的外流和近地面环流最大值与高空中气旋之间较小的分离。这在模拟中促进了近地表垂直涡度的增强。随着剪切层深度和剪切层上的大块剪切强度的变化，近地面垂直涡度作为低层剪切方向的函数也出现了类似的趋势。在不同的深层风廓线或热力学环境下，特定风图形状促进强近地表旋转的程度可能会有所不同；然而，本研究认为，近地面环流极大值和高空中气旋的有利定位是超级单体龙卷风形成的必要条件，这种有利定位可能受到低层风廓线的调节。
Supercell thunderstorms are simulated using an idealized numerical model to analyze the effects of modifications to the environmental low-level wind profile on near-surface rotation. Specifically, the orientation, magnitude, and depth of the low-level vertical wind shear are modified in several suites of experiments and compared to control simulations with no vertical wind shear in the prescribed layer.The overall morphology of the simulated supercells is highly sensitive to even shallow changes in the low-level wind profile. Moreover, maximum near-surface vertical vorticity varies as the low-level wind profile is modified. The results suggest this is principally a consequence of the degree to which favorable dynamic forcing of negatively buoyant outflow is superimposed upon the near-surface circulation maximum. Simulations with easterly shear and weaker storm-relative winds over the depth of the gust front promote forward-surging outflow and smaller separation between the near-surface circulation maximum and the mesocyclone aloft compared with other hodograph shapes. This promotes near-surface vertical vorticity intensification in these simulations. Similar trends in near-surface vertical vorticity as a function of low-level shear orientation are observed for varying shear-layer depths and bulk-shear magnitudes over the shear layer. The degree to which specific hodograph shapes promote strong near-surface rotation may vary with different deep-layer wind profiles or thermodynamic environments from those simulated here; however, this study concludes that favorable positioning of the near-surface circulation maximum and mesocyclone aloft are a necessary condition for supercell tornadogenesis and this positioning may be modulated by the low-level wind profile.
登录
查看更多内容
DOI：
--
发表时间：
2002
期刊：
--
影响因子：
--
作者：
J. Craven;H. Brooks;J. Hart
通讯作者：
J. Craven;H. Brooks;J. Hart
砧遮蔽对模拟超级单体雷暴的动力学影响
影响因子：
3.2
作者：
Jeffrey Frame;P. Markowski
通讯作者：
P. Markowski
影响因子：
3.2
作者：
R. Hastings;Yvette P. Richardson
通讯作者：
R. Hastings;Yvette P. Richardson
影响因子：
3.2
作者：
P. Skinner;C. Weiss;Michael M. French;H. Bluestein;P. Markowski;Yvette P. Richardson
通讯作者：
P. Skinner;C. Weiss;Michael M. French;H. Bluestein;P. Markowski;Yvette P. Richardson
双层剪切流中的密度流
DOI：
--
发表时间：
2007
期刊：
影响因子：
--
作者：
M. Xue
通讯作者：
M. Xue