Cell Merger Potential in Multicell Thunderstorms of Weakly Sheared Environments: Cell Separation Distance versus Planetary Boundary Layer Depth
Cell Merger Potential in Multicell Thunderstorms of Weakly Sheared Environments: Cell Separation Distance versus Planetary Boundary Layer Depth
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DOI：
10.1175//2556.1
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发表时间：
2003-08
影响因子：
3.2
通讯作者：
J. Stalker;K. Knupp
中科院分区：
文献类型：
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作者：
J. Stalker;K. Knupp
使用高分辨率的三维数值实验，本文表明，细胞分离距离尺度为0.75倍的行星边界层（PBL）的深度，成功的细胞合并之间的建设性相互作用的细胞在多细胞雷暴。这种边界层缩放确定从几个模拟的对流细胞对一个固定的PBL深度，并被证明是有效的其他敏感性模拟更大的PBL深度。这项研究建立了一个强大的风暴前的环境条件和细胞合并的潜力有用的多细胞雷暴的多方面的细胞合并过程的研究工作之间的定量关系。1991年8月9日对流和降水/电气化实验（CaPE）的多单体雷暴的弱剪切环境风暴前的条件被用来初始化的细胞对模拟。由于环境风和风切变被假定为零，只有简单的细胞合并，在这项研究中定义为细胞上升气流核心之间的连接，但不重叠的对流阶段，被证明是可能的。Stalker的粗分辨率模拟表明，环境风切变可能是强制单元合并所必需的，在本研究中，强制单元合并定义为初始上升气流核心分离的单元合并。在本研究中，重叠的初始上升气流核心的细胞合并的情况被认为是物理上无效的。
Using high-resolution three-dimensional numerical experiments, this paper shows that the cell separation distance scales as 0.75 times the planetary boundary layer (PBL) depth for successful cell mergers between constructively interacting cells within multicell thunderstorms. This boundary layer scaling is determined from several simulations of convective cell pairs with a fixed PBL depth and is shown to be valid for other sensitivity simulations with larger PBL depths. This research establishes a robust and quantitative relation between prestorm ambient conditions and cell merger potential useful for research efforts on the multifaceted cell merger process of multicell thunderstorms. The weakly sheared ambient prestorm conditions of the 9 August 1991 Convection and Precipitation/Electrification Experiment (CaPE) multicell thunderstorm are used to initialize the cell pair simulations. Since ambient wind and wind shear are assumed to be zero, only simple cell mergers, defined in this study as those between cell updraft cores joined but not overlapping in the convective stage, are shown to be possible. The coarse-resolution simulations of Stalker suggest that ambient wind shear may be necessary for forced cell mergers, defined in this study as those in which the initial updraft cores are found apart. The scenarios of overlapping initial updraft cores for cell merger are considered physically invalid in this study.