A Sensitivity Study of Hodograph-Based Methods for Estimating Supercell Motion
A Sensitivity Study of Hodograph-Based Methods for Estimating Supercell Motion
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基于光速记录仪的超级细胞运动估计方法的灵敏度研究
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
C. Doswell
中科院分区：
文献类型：
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作者：
H. Ramsay;C. Doswell
研究了四种超原胞运动预测算法的速端分析参数。从本文提供的数据中导出的另一种方法，即所谓的偏移方法，用于使用观测到的风暴运动和平均风来制定上述方案的基线标准。它不是一个预报方案，因为它是基于对观测到的风暴运动的了解。这项工作探讨了这些算法的敏感性，他们的任意参数，系统地改变这些参数，使用394右移动的超级细胞的数据集，和相关的接近探测。在这些算法中使用的参数，以定义平流层深度和/或传播的超级单体尚未被证明是最佳的为此目的。这些任意参数组成平均风层的顶部和底部水平，以及通过该层定义的平均风的偏差矢量。两个最近开发的算法也实现了垂直风切变矢量在任意层深。已经发现，在其他结果中，使用平均风和垂直风切变的方案对平均风层的深度比对垂直风切变层的深度更敏感。还表明，当使用最简单的方案时，平均而言，通过使用深层平均风层（即，大于0-10公里）。事实上，所有的预报方案都显示出强烈的趋势，即预报风暴运动的u分量受平均风层深度的调节。另一方面，预测风暴运动的分量似乎受层平均风的偏差矢量控制。虽然使用垂直切变的方案比仅基于平均风的方案平均表现更好，但有时它们也会导致较大的预报误差。结果表明，在使用观察到的速端预测超单体运动的固有困难。
Four supercell motion forecast algorithms are investigated with respect to their hodograph-analysis parameters. Another method derived from the data presented herein, the so-called offset method, is used to develop a baseline standard for the aforementioned schemes, using the observed storm motions and the mean wind. It is not a forecast scheme, as it is based on knowing the observed storm motions. This work explores the sensitivity of these algorithms to their arbitrary parameters by systematically varying those parameters, using a dataset of 394 right-moving supercells, and associated proximity soundings. The parameters used in these algorithms to define the layer depths for advection and/or propagation of supercells have not been shown to be optimum for this purpose. These arbitrary parameters compose the top and bottom levels of the mean wind layer, and a deviation vector from the mean wind defined through that layer. Two of the most recently developed algorithms have also implemented the vertical wind shear vector over an arbitrary layer depth. It has been found that, among other results, the scheme using both mean wind and vertical wind shear is more sensitive to the depth of the mean wind layer than it is to the depth of the vertical wind shear layer. It has also been shown that, when using the simplest schemes, the most accurate forecasts, on average, are obtained by using deep mean wind layers (i.e., greater than 0–10 km). Indeed, all the forecast schemes show a strong tendency for the u component of the predicted storm motion to be regulated by the depth of the mean wind layer. The component of the prediction storm motion, on the other hand, appears to be controlled by the deviation vector from the layer-mean wind. Although the schemes using vertical shear are shown to perform somewhat better on average than schemes based on the mean wind alone, there are times in which they also result in large forecast errors. The results demonstrate the inherent difficulty in using an observed hodograph to predict supercell motion.