Distinguishing Characteristics of Tornadic and Nontornadic Supercell Storms from Composite Mean Analyses of Radar Observations
Distinguishing Characteristics of Tornadic and Nontornadic Supercell Storms from Composite Mean Analyses of Radar Observations
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从雷达观测的综合平均分析中区分龙卷风和非龙卷风超级单体风暴的特征
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发表时间：
2020
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影响因子：
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通讯作者：
A. Murphy
中科院分区：
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作者：
C. Homeyer;T. Sandmæl;C. Potvin;A. Murphy
为了更好地理解龙卷风和非龙卷风超级单体之间的共同差异，研究人员使用了位于美国邻近地区的NEXRAD WSR-88D极化雷达网的大量观测数据。特别是，在7年期间（2011-17年），478个非龙卷风和294个龙卷风超级单体的数据被用来产生微物理和运动学变量的概率匹配复合平均值。平均值以回波顶最大值为中心，在一个水平坐标系中旋转，使风暴运动点处于x正维，这些平均值是在相对于地面的高度产生的，在非龙卷风超级单体的回波顶高度峰值和中层旋转峰值的时间，以及在龙卷风超级单体中第一个龙卷风出现的时间和之前。超级单体类型之间存在显著差异，在龙卷风形成时和之前具有一致的特征。特别地，中气旋在龙卷风超级单体中垂直排列，而在非龙卷风超级单体中则不排列。发现的微物理差异包括：在龙卷风超级单体中，低空雷达反射率钩回波对准风暴中心右侧约10公里，而在非龙卷风超级单体中，低空雷达反射率钩回波向下移动5-10公里；在龙卷风超级单体中，低空雷达反射率偶极子更平行于风暴运动，而在非龙卷风超级单体中更垂直于风暴运动；在低层，增强的差分雷达反射率和特定的差分相位（具有独特的位移相对相关系数降低）之间的分离，在龙卷风超级单体中更垂直于风暴运动，而在非龙卷风超级单体中更平行。
An improved understanding of common differences between tornadic and nontornadic supercells is sought using a large set of observations from the operational NEXRAD WSR-88D polarimetric radar network in the contiguous United States. In particular, data from 478 nontornadic and 294 tornadic supercells during a 7-yr period (2011–17) are used to produce probability-matched composite means of microphysical and kinematic variables. Means, which are centered on echo-top maxima and in a horizontal coordinate system rotated such that storm motion points in the positive x dimension, are created in altitude relative to ground level at times of peak echo-top altitude and peak midlevel rotation for nontornadic supercells and times at and prior to the first tornado in tornadic supercells. Robust differences between supercell types are found, with consistent characteristics at and preceding tornadogenesis in tornadic storms. In particular, the mesocyclone is found to be vertically aligned in tornadic supercells and misaligned in nontornadic supercells. Microphysical differences found include a low-level radar reflectivity hook echo aligned with and ~10 km right of storm center in tornadic supercells and displaced 5–10 km down-motion in nontornadic supercells, a low-to-midlevel differential radar reflectivity dipole that is oriented more parallel to storm motion in tornadic supercells and more perpendicular in nontornadic supercells, and a separation between enhanced differential radar reflectivity and specific differential phase (with unique displacement-relative correlation coefficient reductions) at low levels that is more perpendicular to storm motion in tornadic supercells and more parallel in nontornadic supercells.