Using the Translation Speed and Vertical Structure of Gust Fronts to Infer Buoyancy Deficits within Thunderstorm Outflow
Using the Translation Speed and Vertical Structure of Gust Fronts to Infer Buoyancy Deficits within Thunderstorm Outflow
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利用阵风锋的平移速度和垂直结构来推断雷暴流出中的浮力不足
DOI：
10.1175/mwr-d-18-0439.1
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发表时间：
2019
影响因子：
3.2
通讯作者：
Bryan, George
中科院分区：
文献类型：
--
作者：
Hutson, Abby;Weiss, Christopher;Bryan, George
本研究探讨能否从后方阵风锋面的传播速度和垂直结构来推断超级单体后方外流的热力学。为了量化外流热力亏损与阵风锋面结构之间的关系，采用CM1作为二维冷池模式，评估了不同环境切变构型下不同强度冷池的垂直斜率。模式在自由滑移和半滑移下边界条件下运行，并将结果与德克萨斯理工大学Ka波段移动雷达捕获的强雷暴外流观测结果进行了比较。在自由滑移模型中模拟的冷池达到了冷池理论所预测的传播速度，而在半滑移模型中模拟的冷池速度传播较慢。将密度流理论应用于观测到的冷池，并预测冷池速度约为2m S−1。自由滑移和半滑移模式的结果都表明，在相同的切变流动中，强冷池的边缘比弱冷池的边缘倾斜度小。弱环境切变条件下的冷池比强环境切变条件下的冷池具有更大的坡度。对两个模型的数据进行了非线性回归，得到了斜率与浮力和切变的适当关系，但自由滑移模型不能在可接受的误差范围内预测观测斜率，而半滑移模型对所有观测情况的冷池斜率都有过高的预测，但由于切变估计存在不确定性。
This study investigates whether the thermodynamics of supercell rear-flank outflow can be inferred from the propagation speed and vertical structure of the rear-flank gust front. To quantify the relationship between outflow thermodynamic deficit and gust front structure, CM1 is applied as a two-dimensional cold pool model to assess the vertical slope of cold pools of varying strength in different configurations of ambient shear. The model was run with both free-slip and semislip lower boundary conditions and the results were compared to observations of severe thunderstorm outflow captured by the Texas Tech University Ka-band mobile radars. Simulated cold pools in the free-slip model achieve the propagation speeds predicted by cold pool theory, while cold pool speeds in the semislip model propagate slower. Density current theory is applied to the observed cold pools and predicts the cold pool speed to within about 2 m s−1. Both the free-slip and semislip model results reveal that, in the same sheared flow, the edge of a strong cold pool is less inclined than that of a weaker cold pool. Also, a cold pool in weak ambient shear has a steeper slope than the same cold pool in stronger ambient shear. Nonlinear regressions performed on data from both models capture the proper dependence of slope on buoyancy and shear, but the free-slip model does not predict observed slopes within acceptable error, and the semislip model overpredicts the cold pool slope for all observed cases, but with uncertainty due to shear estimation.
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影响因子：
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DOI：
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发表时间：
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DOI：
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