A Case Study of Terrain Influences on Upscale Convective Growth of a Supercell
A Case Study of Terrain Influences on Upscale Convective Growth of a Supercell
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DOI：
10.1175/mwr-d-19-0099.1
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发表时间：
2019-11
影响因子：
3.2
通讯作者：
J. Mulholland;S. Nesbitt;R. Trapp
中科院分区：
文献类型：
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作者：
J. Mulholland;S. Nesbitt;R. Trapp
卫星和地面雷达观测表明，南美洲阿根廷的北方是一个易受深层湿对流快速增长为较大的有组织的中尺度对流系统（MCS）的区域。特别是，假设科尔多瓦山脉的复杂地形对这一升级增长过程至关重要。一个典型的地形超级单体到MCS过渡的案例研究进行了分析，以确定复杂的地形对高档对流增长过程的影响。进行了高分辨率数值模拟试验，通过提高或降低1 000米以上的地形高度，系统地修改了科尔多瓦山脉的地形高度。地形的改变对风暴形态有直接和间接的影响。直接影响包括地形对冷池的阻挡，而间接影响包括地形引起的相关风暴环境参数的变化（例如，垂直风切变、对流可用势能）。当地形升高时，低层和深层垂直风切变增加，混合层对流有效位能减少，深层湿对流启动提前，冷池受阻，且普遍变强变深。当地形降低时，情况正好相反，导致一个较弱的超级单体不能成长为MCS。控制模拟超级单体显示了最深的冷池和相应的最快的过渡从超级单体到MCS，可能揭示了独特的地形配置的Sierras de科尔多瓦是支持观察到的快速高档对流增长的地形超级单体。
Satellite- and ground-based radar observations have shown that the northern half of Argentina, South America, is a region susceptible to rapid upscale growth of deep moist convection into larger organized mesoscale convective systems (MCSs). In particular, the complex terrain of the Sierras de Córdoba is hypothesized to be vital to this upscale-growth process. A canonical orographic supercell-to-MCS transition case study was analyzed to determine the influence that complex terrain had on processes governing upscale convective growth. High-resolution numerical modeling experiments were conducted in which the terrain height of the Sierras de Córdoba was systematically modified by raising or lowering the elevation of terrain above 1000 m. The alteration of the terrain lead to both direct and indirect effects on storm morphology. A direct effect included terrain blocking of cold pools, whereas indirect effects included terrain-induced variations in pertinent storm environmental parameters (e.g., vertical wind shear, convective available potential energy). When the terrain was raised, low-level and deep-layer vertical wind shear increased, mixed-layer convective available potential energy decreased, deep moist convection initiated earlier, and cold pools were blocked and generally became stronger and deeper. The reverse occurred when the terrain was lowered, resulting in a weaker supercell that did not grow upscale into an MCS. The control simulation supercell displayed the deepest cold pool and correspondingly fastest transition from supercell to MCS, potentially revealing that the unique terrain configuration of the Sierras de Córdoba was supportive of the observed rapid upscale convective growth of this orographic supercell.