Squall lines are known to be the consequence of the interaction of low-level shear with cold pools associated with convective downdrafts. Also, as the magnitude of the shear increases beyond a critical shear, squall lines tend to orient themselves. The existing literature suggests that this orientation reduces incoming wind shear to the squall line, and maintains equilibrium between wind shear and cold pool spreading. Although this theory is widely accepted, very few quantitative studies have been conducted on supercritical regime especially. Here, we test this hypothesis with tropical squall lines obtained by imposing a vertical wind shear in cloud resolving simulations in radiative convective equilibrium. In the sub-critical regime, squall lines are perpendicular to the shear. In the super-critical regime, their orientation maintain the equilibrium, supporting existing theories. We also find that as shear increases, cold pools become more intense. However, this intensification has little impact on squall line orientation.

中文翻译：

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热带飑线的切变-对流相互作用和方向

众所周知，飑线是低层切变与与对流下降气流相关的冷池相互作用的结果。此外，随着切变的幅度增加到超过临界切变，飑线往往会自行定向。现有文献表明，这种方向减少了进入飑线的风切变，并保持风切变和冷池扩散之间的平衡。尽管这一理论被广泛接受，但很少有人对超临界状态进行定量研究。在这里，我们用通过在辐射对流平衡中的云解析模拟中施加垂直风切变获得的热带飑线来检验这一假设。在亚临界状态下，飑线垂直于切变。在超临界状态下，他们的方向保持平衡，支持现有的理论。我们还发现，随着切变的增加，冷池变得更加强烈。然而，这种强化对飑线方向的影响不大。