The Impact of Terrain on Three Cases of Tornadogenesis in the Great Tennessee Valley
The Impact of Terrain on Three Cases of Tornadogenesis in the Great Tennessee Valley
复制标题
地形对大田纳西河谷龙卷风发生的三个案例的影响
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
D. Schneider
中科院分区：
文献类型：
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作者：
D. Schneider
与西田纳西州和中田纳西州相比，东田纳西州大田纳西河谷遭受的龙卷风要少得多。这种差异的部分原因是大田纳西河谷复杂的地形。山谷的总体方向是西南向东北，这通常不利于近地表流向南或东南方向的低位支持。然而，在较大的山谷内，存在较小的地理特征，可以导致气候上有利于向东移动的对流系统的风暴相对螺旋度的局部增强。本研究检查了大田纳西河谷发生的三起龙卷风事件，以确定地形对龙卷风发生的影响。在一个或多个所研究的案例中，龙卷风发生的可能性似乎因以下原因而增强：1）较小山谷相对于盛行气流的方向导致近地表风的通道和后退，导致局部增强的风暴相对螺旋度； 2）当风暴从较高地形移动到较低地形时，涡度的垂直拉伸增加了中气旋强度； 3) 上升气流导致风暴上升气流增强和中气旋增强； 4）山体屏障作为边界，边界以北有更有利的龙卷风环境。
The Great Tennessee Valley of East Tennessee has experienced significantly fewer tornadoes in comparison to West and Middle Tennessee. This discrepancy can partly be explained by the complex terrain of the Great Tennessee Valley. The general orientation of the valley is southwest to northeast, which is typically not conducive to low level backing of the near-surface flow to a south or southeasterly direction. However, within the larger valley there are smaller geographical features that can lead to localized enhancement of storm-relative helicity for climatologically favored eastward-moving convective systems. This study examines three tornado events that occurred in the Great Tennessee Valley to determine the impact of topography on tornadogenesis. In one or more of the examined cases, the potential for tornadogenesis appears to have been enhanced by 1) the orientation of smaller valleys relative to the prevailing flow causing the channeling and backing of near-surface winds, resulting in locally enhanced storm-relative helicity; 2) vertical stretching of vorticity increasing mesocyclone strength when storms move from higher terrain to lower terrain; 3) upslope flow leading to intensification of storm updrafts and a strengthening mesocyclone; 4) mountain barriers acting as a boundary, with a more favorable tornado environment north of the boundary.