Lightning Frequency in an Idealized Hurricane-Like Vortex from Initial to Steady-State Using a Coupled Meteorological and Explicit Bulk Lightning Model
Lightning Frequency in an Idealized Hurricane-Like Vortex from Initial to Steady-State Using a Coupled Meteorological and Explicit Bulk Lightning Model
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DOI：
10.1175/mwr-d-20-0110.1
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发表时间：
2021-03
影响因子：
3.2
通讯作者：
Yousuke Sato;Y. Miyamoto;H. Tomita
中科院分区：
文献类型：
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作者：
Yousuke Sato;Y. Miyamoto;H. Tomita
利用一个三维气象模式和一个显式闪电模式，研究了闪电频率对一个理想化热带气旋生命周期的依赖性。为了研究这种依赖性，进行了理想化的数值模拟，涵盖了理想化TC的初始状态到稳态（SS）。模拟结果与以往观测研究中闪电频率随时间的变化趋势一致。我们的分析表明，依赖性起源于在TC的生命周期中的对流云与闪电的类型的变化。在快速增强（RI）之前和RI的早期阶段，在高对流有效位能（CAPE）条件下形成的对流云单体是闪电的主要贡献者。当TC到达RI后期并接近SS时，次级环流变得突出，并在次级环流旁边的眼壁区域的对流云逐渐成为闪电的主要贡献者。在高CAPE条件下形成的对流云单体中，上升速度很强，并且通过<$子碰撞引起的非感应电荷分离提供了大的电荷密度。这种大的电荷密度经常在云中引发闪电。另一方面，眼壁垂直速度较弱，只有在热带气旋发展到成熟阶段时，眼壁垂直速度才对闪电有贡献。我们的分析意味着，最大的闪电频率之前发生的TC的最大强度对应的阶段的TC的生命周期中，对流云细胞产生最频繁，湿润对流层上部。
The dependence of lightning frequency on the life cycle of an idealized tropical cyclone (TC) was investigated using a three-dimensional meteorological model coupled with an explicit lightning model. To investigate this dependence, an idealized numerical simulation covering the initial state to the steady state (SS) of an idealized TC was conducted. The simulation was consistent with the temporal evolution of lightning frequency reported by previous observational studies. Our analyses showed that the dependence originates from changes in the types of convective cloud with lightning over the life cycle of the TC. Before rapid intensification (RI) and in the early stage of RI, convective cloud cells that form under high-convective available potential energy (CAPE) conditions are the main contributors to lightning. As the TC reaches the late stage of RI and approaches SS, the secondary circulation becomes prominent and convective clouds in the eyewall region alongside the secondary circulation gradually become the main contributors to the lightning. In the convective cloud cells formed under high-CAPE conditions, upward velocity is strong and large charge density is provided through noninductive charge separation induced by graupel collisions. This large charge density frequently induces lightning in the clouds. On the other hand, the vertical velocity in the eyewall is weak, and it tends to contribute to lightning only when the TC reaches the mature stage. Our analyses imply that the maximum lightning frequency that occurs before the maximum intensity of a TC corresponds to the stage of a TC’s life cycle in which convective cloud cells are generated most frequently and moisten the upper troposphere.