Microphysical Structure and Lightning Initiation in Hokuriku Winter Clouds
Microphysical Structure and Lightning Initiation in Hokuriku Winter Clouds
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DOI：
10.1029/2018jd030227
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
T. Takahashi;S. Sugimoto;Tetsuya Kawano;K. Suzuki
中科院分区：
文献类型：
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作者：
T. Takahashi;S. Sugimoto;Tetsuya Kawano;K. Suzuki
北陆冬季的云层会从相对较浅的云层中产生频繁的正闪电。为了理解这一现象，从日本柏崎发射的Videosondes和Videosonde-HYVIS联合探空仪的数据与雷达和闪电定位系统网络数据进行了分析。主要的电荷载体是霰粒子和冰晶，和空间电荷增加与他们的数量浓度一致的雾凇起电。在云的生命过程中，云的结构发生了很大的变化。在成熟阶段，云上层空间电荷为正（由正冰晶携带），中层空间电荷为负（由负<$球和负冰晶携带），下层空间电荷为正（由正<$球携带）。闪电只出现在具有以下所有特征的云层中：云顶温度1.2 km，空间电荷>2-3 pC/L，冰晶数浓度>500 m−3，和粒子数浓度>20 m−3。正性云地闪电的优势与<$p数浓度<200 m−3和<$p峰值直径≤4 mm有关。+CG闪电区倾向于从−CG闪电区向下剪切。资料表明，−CG主要由对流单体中的中层负启动，而+CG则由高空正冰晶启动，并被风切变移动和下降。冰晶数密度的一个主要贡献者是一种新的冰增殖过程，在这种过程中，大量的<$apel表面冰分支被折断，随后生长成冰晶。
Hokuriku winter clouds produce frequent, positive lightning from relatively shallow clouds. To understand this phenomenon, data from Videosondes and Videosonde‐HYVIS conjoined sondes, launched from Kashiwazaki, Japan, were analyzed with radar and Lightning Location System network data. The main charge carriers were graupel particles and ice crystals, and space charge increased with their number concentrations consistent with riming electrification. Cloud structure evolved greatly over the course of cloud life. In the mature stage, space charge was positive in the cloud upper level (carried by positive ice crystals), negative in the middle level (carried by negative graupel and negative ice crystals), and positive in the lower level (carried by positive graupel). Lightning was only seen in clouds that had all of the following characteristics: cloud top temperature 1.2 km, space charge >2–3 pC/L, ice crystal number concentration >500 m−3, and graupel particle number concentration >20 m−3. Predominance of positive cloud‐to‐ground (+CG) lightning was associated with graupel number concentration <200 m−3 and graupel peak diameter ≤4 mm. The +CG strike zone tended to be downshear from the −CG strike zone. The data suggest that −CG is initiated mainly by middle‐level negative graupel in the convective cell, while +CG is initiated by positive ice crystals in the upper domain, displaced by wind shear and descending. A major contributor to ice crystal number density is a novel ice multiplication process in which graupel‐surface ice branches are broken‐off in large numbers and subsequently grow into ice crystals.