Investigating the Transition from Elevated Multicellular Convection to Surface-Based Supercells during the Tornado Outbreak of 24 August 2016 Using a WRF Model Simulation
Investigating the Transition from Elevated Multicellular Convection to Surface-Based Supercells during the Tornado Outbreak of 24 August 2016 Using a WRF Model Simulation
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使用 WRF 模型模拟研究 2016 年 8 月 24 日龙卷风爆发期间从高位多细胞对流到地基超级细胞的转变
DOI：
10.1175/waf-d-18-0209.1
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发表时间：
2019
影响因子：
2.9
通讯作者：
Jeffrey W. Frame
中科院分区：
文献类型：
--
作者：
Kevin T. Gray;Jeffrey W. Frame
2016年8月24日，印第安纳州、俄亥俄州和安大略省爆发龙卷风，造成26次龙卷风。高空的多细胞对流发展成基于地表的超级细胞，产生了几个龙卷风，特别是在差热边界附近。由于这种对流模式的转变相对罕见，因此特别令人感兴趣。WRF模型的模拟准确地捕捉到了这次爆发期间的环境和风暴演变。轨迹分析表明，多细胞上升气流最初是升高的。由于几乎所有的垂直风切变都被限制在最低的1公里处，在风暴开始吸收近地面空气之前，水平涡度的倾斜并没有产生显著的旋转。由于垂直混合，近地面垂直风切变在云层外减少，而它在铁砧下被保留，使得0 - 1公里的风暴相对螺旋度的大值在差异加热边界以北持续存在。WRF模式输出的扰动压力场分析表明，相对较大的非线性垂直扰动压力梯度的发展与近地面空气开始进入上升气流的时间一致，导致最低2 km处的上升加速度低于最大旋转水平。在加强上升气流的过程中，向上的浮力扰动压力加速度可能抵消了最大旋转水平以上的向下的非线性扰动压力加速度，从而使上升气流进一步加强。
On 24 August 2016, a tornado outbreak impacted Indiana, Ohio, and Ontario with 26 confirmed tornadoes. Elevated multicellular convection developed into surface-based supercells that produced several tornadoes, particularly near a differential heating boundary. This convective mode transition is of particular interest owing to its relatively rare occurrence. A WRF Model simulation accurately captures the environment and storm evolution during this outbreak. Trajectory analyses indicate that the multicellular updrafts were initially elevated. Since nearly all of the vertical wind shear was confined to the lowest 1 km, significant rotation did not develop via tilting of horizontal vorticity until the storms began ingesting near-surface air. Near-surface vertical wind shear decreased outside of cloud cover owing to vertical mixing, while it was preserved under the anvil, allowing for large values of 0–1-km storm-relative helicity to persist north of a differential heating boundary. Analysis of the perturbation pressure field from the WRF Model output indicates that the development of relatively large nonlinear vertical perturbation pressure gradients coincided with when near-surface air began to enter the updrafts, resulting in upward accelerations in the lowest 2 km, below the level of maximum rotation. In strengthening updrafts, upward-directed buoyancy perturbation pressure accelerations may have offset the downward-directed nonlinear perturbation pressure accelerations above the level of maximum rotation, allowing the updrafts to intensify further.
影响因子：
3.2
作者：
J. Marsham;S. Trier;T. Weckwerth;James W. Wilson
通讯作者：
J. Marsham;S. Trier;T. Weckwerth;James W. Wilson
影响因子：
3.1
作者：
S. Trier;J. Marsham;C. Davis;D. Ahijevych
通讯作者：
S. Trier;J. Marsham;C. Davis;D. Ahijevych