Lightning location relative to storm structure in a leading-line, trailing-stratiform mesoscale convective system
Lightning location relative to storm structure in a leading-line, trailing-stratiform mesoscale convective system
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DOI：
10.1029/2003jd004371
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发表时间：
2005-02-01
影响因子：
4.4
通讯作者：
Demetriades, NWS
中科院分区：
文献类型：
--
作者：
Carey, LD;Murphy, MJ;Demetriades, NWS
[1]2002年6月16日，达拉斯-沃斯堡闪电探测和测距(LDAR II)甚高频辐射源和雷达反射率的水平和线法线垂直截面和合成图像提供了一个独特的视角，显示了2002年6月16日在前线、拖尾层状(LLTS)中尺度对流系统(MCS)内的闪电路径。绝大多数VHF闪电源沿垂直方向呈双峰型出现在超前对流线内。假定甚高频源密度极大值很可能与正电荷有关，那么激光雷达II观测表明，MCS对流区的总电荷结构是一个三极，净正电荷集中在4.5公里AGL(3度C)和9.5公里AGL(-35度C)，净负电荷大致集中在VHF源密度最大值的相对最小处7公里AGL(-17度C)。持续闪电路径和推测的正电荷区在对流线上向后倾斜(40-50公里)，向下倾斜(4-5公里)，穿过过渡区，进入层状区的雷达亮带。在层状区，VHF闪电源和推测的正电荷集中在4.5、6和9 km AGL(分别为2度C、-11度C和-31度C)的三层中，这与以往对对称LLTS MCSs的电场研究一致。层状区的正地闪电起源于对流线，沿倾斜路径从对流核顶进入层状降水，具有水平广泛性、层状性和高度分支性。倾斜的闪电路径与雪粒的假设轨迹相同。这些观测结果进一步支持了雪上电荷沿倾斜路径的平流和水平闪电层中电荷的就地产生，它们是对流线后面带电和正闪电产生的主要贡献者。
[ 1] Horizontal and line-normal, vertical cross-sections and composite images of Dallas-Fort Worth Lightning Detection and Ranging ( LDAR II) VHF radiation sources and radar reflectivity over a 30-min period provide a unique perspective on lightning pathways within a leading-line, trailing-stratiform ( LLTS) mesoscale convective system ( MCS) on 16 June 2002. The overwhelming majority of VHF lightning sources occurred within the leading convective line in a bimodal pattern in the vertical. Assuming that VHF source density maxima were most likely associated with positive charge, then the LDAR II observations suggest that the gross charge structure of the convective region of the MCS was characterized by a tripole with net positive charge centered at 4.5 km AGL ( 3 degreesC) and 9.5 km AGL ( -35 degreesC) and net negative charge centered roughly in the relative minimum of the VHF source density maximum at 7 km AGL ( -17 degreesC). A persistent lightning pathway and inferred positive charge zone sloped rearward ( by 40-50 km) and downward ( by 4-5 km) from the upper VHF source maximum in the convective line, through the transition zone, and into the radar bright band of the stratiform region. In the stratiform region, VHF lightning sources and inferred positive charge were concentrated in three layers centered at 4.5, 6, and 9 km AGL ( 2 degreesC, -11 degreesC, and -31 degreesC, respectively), consistent with past electric field studies of symmetric LLTS MCSs. Positive cloud-to-ground lightning flashes in the stratiform region were initiated in the convective line and followed the slanting pathway from the top of convective cores to the stratiform precipitation, where they were horizontally extensive, layered, and highly branched. The sloping lightning pathway was identical to hypothetical trajectories taken by snow particles. These observations provide further support for the advection of charge on snow along the sloping pathway and the in situ generation of charge in the horizontal lightning layers as primary contributors to electrification and positive lightning production rearward of the convective line.