山东地区冰雹云的闪电活动特征

利用山东电力部门提供的雷电定位资料,对10次冰雹过程的地闪活动特征进行了分析。通过分析发现,雹暴中正地闪占总地闪的比例平均为57.39％,远高于当地正地闪比例的气候特征值13.48％。地面降雹区基本出现在正地闪密集（活跃）区或邻近区域。在雹云快速发展阶段,地闪频数存在明显的“跃增”;在减弱消散阶段,地闪频数显著减少,但正地闪比例有所提高。负地闪频数峰值的出现通常提前于降雹0～20 min,正地闪频数峰值的出现一般滞后于降雹发生时间。整个降雹阶段对应于正地闪的活跃阶段。另外,结合对卫星观测的总闪电资料分析,发现冰雹云的云闪与地闪的比值远高于一般的雷雨过程,其云闪密度也远高于雷雨过程。以上这些特征对于冰雹的识别和对冰雹的超短时预报具有指示意义。     

基于TRMM/LIS资料的浙江省及周边地区闪电特征和气象要素分析

利用TRMM/LIS 0.1°超高分辨率闪电定位产品, 分析了浙江省及周边地区(117.5~123.0°E, 26~32°N)卫星闪电资料的时空分布特点; 并结合中国区域地面气象要素驱动数据集、亚洲大陆气溶胶光学厚度数据集, 分析了该区域闪电与气象要素的关系。结果表明: 研究区域内闪电平均密度为5.97 f1/(km2·a), 其中陆地闪电平均密度为7.94 f1/(km2·a), 海洋闪电平均密度为2.09 f1/(km2·a), 陆地闪电平均密度为海洋闪电平均密度的3.80倍; 平均闪电密度值逐月变化特征在陆地和海洋区域有很好的一致性, 夏季闪电密度最大, 冬季闪电密度值最小; 陆地闪电密度日变化呈现单峰结构, 海洋闪电密度日变化呈现双峰双谷波形。该区域陆地气温、地面辐射、比湿及降水率均与闪电密度的月变化成正相关, 其中地面降水率和闪电密度月变化相关系数最高, 为0.858 0;气溶胶光学厚度与闪电密度月变化呈现弱的负相关, 相关系数为-0.397 8。      

A multiparameter radar case study of the microphysical and kinematic evolution of a lightning producing storm

Summary We examine the co-evolving microphysical, kinematic, and electrical characteristics of a multi-cell thunderstorm observed on 21 May 1993 along the Front Range of Colorado using data collected with the 11 cm, multiparameter, CSU-CHILL Doppler radar. The measured polarimetric variables provide information on the size, shape, orientation, and thermodynamic phase of hydrometeors. Recent modeling and observational advances in weather radar polarimetry now permit the inference of bulk-hydrometeor types and mixing ratios, and the measurement of precipitation rate in mixed-phase (i.e., hail and rain) environments. We have employed these and other radar techniques, such as dual-Doppler analyses, to investigate the correlation between the convective life cycle of a multi-cell storm and the evolution of lightning type and flash rate.The observations suggest a strong correlation between the radar-inferred graupel volume suspended in a vigorous updraft in upper-portions of the storm and the in-cloud (IC) lightning flash rate. Our analyses reveal that maxima in the hail rate are related to peaks in the cloud-to-ground (CG) lightning flash rate. Both correlation's are consistent with the non-inductive charging mechanism which relies on collisions between graupel/hail particles and ice crystals in the presence of supercooled water. Peaks in storm outflow are shown to either lag or to coincide with maxima in both the CG flash rate and hail rate. The amount and vertical location of ice in this storm was also related to the strength and polarity of the electric field through observations of a Field Excursion Associated With Precipitation (FEAWP) and a subsequent microburst. We demonstrate that the FEAWP was coincident with the descent of graupel and small hail below the charge reversal level as explained by the non-inductive charging mechanism, and that the further descent of graupel and small hail below the melting level aided in the generation of a microburst near the surface. Using observations of the FEAWP, we present some comparative speculation on the microphysics of the associated lower positive charge center and the applicability of various laboratory charging studies.With 14 Figures     

Characteristics of the two active stages of lightning activity in two hailstorms

Two hailstorms that occurred in Beijing and Tianjin, respectively, are investigated, based mainly on the total lightning data observed by the System d’Alerte Fondre par Interferometric Radioelecctrique (SAFIR3000), the cloud-to-ground (CG) lightning data of a CG lightning location system, and the echo data of a Doppler radar. Both hailstorms exhibited two lightning frequency peaks: the first was before the hailfall and the second was after the hailfall, with the second peak greater than the first. The dominant polarity of the CG lightning was positive in the stage around the first frequency peak, but changed to negative in the stage around the second frequency peak. The evolution of radar echoes and the height distribution of lightning radiation sources are explored, revealing that both hailstorms had stronger convection and the main positive charge occurred at mid levels during the stage around the first frequency peak. However, whilst the Beijing hailstorm experienced the enhancement of convection, with the main positive charge at upper levels around the second frequency peak, the Tianjin hailstorm generated its second frequency peak during the period when the convection kept weakening and the main positive charge dropped to mid–lower levels. Through evaluation of the radar parameters, we investigate the mechanisms responsible for the second stage of active lightning discharge. Furthermore, the lightning activity exhibited a close relationship with radar echo parameters and hailfall. Lightning jump signals were found before the hailfall and were associated with the change ratio of the 40-dBZ echo volume above the ?15°C level, which demonstrates the application value of lightning data in severe weather warning.     

青藏高原中部闪电活动与相关气象要素季节变化的相关分析

利用 1995年 4月至 2 0 0 2年 12月间卫星观测的闪电资料与NCEP再分析资料中的地表降水率、云功函数和热通量 ,分析了青藏高原中部闪电活动与相关气象要素季节变化之间的关系。研究发现 :青藏高原中部闪电活动的峰值出现在 7月份 ,并在春季表现出明显的闪电活动 ;相关气象要素中 ,最能够准确描述闪电活动的季节变化及其春季异常特征的仅有地表总热通量 ;降水 (或云功函数 )与鲍恩比 (感热通量和潜热通量之比 )的乘积能够较好地反映闪电活动的季节分布特征与春季的“异常”。结果表明 ,感热通量或鲍恩比可能在对流有效位能向对流上升动能的转化过程中起着重要的作用 ,鲍恩比可作为修正闪电产生效率的一个重要参量。     

放电后电荷重置对雷暴云电荷结构及闪电行为的影响

为探究放电后电荷重置对雷暴云电过程的影响,在已有的三维雷暴云起、放电模式中分别加入两种不同的电荷重置方案:一种是植入法即放电后闪电通道上的感应电荷与原空间电荷叠加(简称ZR方案);另一种是中和法即放电后直接按一定比例降低闪电通道处的空间电荷浓度(简称ZH方案)。利用长春一次探空个例进行敏感性试验,发现放电后重置方式的不同会导致闪电特征存在明显差异:1)ZR方案下的云闪发生率比ZH方案下的云闪发生率少。闪电放电后ZR方案在云中植入异极性电荷,对雷暴云中电荷的中和量比ZH方案多,摧毁云中电场的能力更强;2)ZR方案下的正、负地闪发生率均比ZH方案多。相对于ZH方案,ZR方案中主正电荷区的分布范围大于主负电荷区,导致其出现了更多的正地闪;ZR方案中的云顶屏蔽层与主正电荷区的混合程度高,混合时间长,导致ZR方案在主正电荷区与主负电荷区之间触发了更多的负地闪;3)ZR方案下的闪电通道长度比ZH方案下的闪电通道长度短。ZR方案在云中植入异极性电荷,导致云中难以形成大范围同极性电荷堆,闪电通道传播局限在一对较小的异极性电荷堆内,而ZH方案不改变云中电荷分布,存在大范围同极性电荷堆,闪电通道传播范围较大。     

广东地闪时空特征及与降水关系分析

利用2016-2020年粤港澳闪电定位数据和广东86个国家地面观测站逐小时降水资料,分析了广东地闪频次和地闪强度的时空分布特征,以及地闪与降水量、强降水频次之间的相关关系.结果表明:(1)广东逐月地闪频次与降水变化均呈双峰型分布,峰值在6和8月,两者相关系数达到0.95.日变化中,地闪频次高值集中在12:00-20:0...     

Some aspects of the correlation between lightning and rain activities in thunderstorms

The lightning activity of convective systems is a sometimes fruitful indicator of their precipitation production. The present study compares rain volume with different types of lightning activity in several convective systems. The study uses data obtained in the Paris area where two lightning detection systems coexist. The Météorage network provides the location and the polarity of cloud-to-ground flashes, while the SAFIR system detects the total flash activity: cloud-to-ground, intra-cloud flashes and VHF individual sources within a given time window. The overall spatial correlation between rain and lightning appears to be very consistent for all lightning types. A pixel-to-pixel study shows that positive CG flashes are associated with higher rainwater volume than negative flashes. Introducing a weight coefficient for positive CG flashes considerably improves the correlation between rain amount and lightning production. Taking into account the specific contribution of each type of lightning flash, the amount of rain can be estimated from the total electrical activity of each system. Comparison with the amount derived from radar measurement shows reasonable agreement. Finally, the parallel time evolutions of rain and lightning rates display quite similar characteristics.     

暴雨和雹暴个例中闪电特征对比

暴雨与雹暴过程中对应的闪电活动特征显著不同,为了对比这两类对流过程中的闪电活动特征差异,该文选取了两种比较有代表性的雷暴个例——暴雨过程和雹暴过程,利用全闪（包括云闪与地闪）定位数据,分析了两者闪电活动特征以及闪电活动与对流降水之间的关系。研究发现:暴雨过程中地闪频次和正地闪比例均低于雹暴过程;相对于暴雨过程,雹暴过程的主正电荷区放电高度更高,主正电荷区所处的温度偏低;暴雨过程中,总闪频次与对流降水量、总闪频次与对流降水强度的相关性均优于雹暴过程。总体而言,雹暴过程中闪电活动特征及其与降水的关系更为复杂,这可能与雹暴过程具有更为复杂的动力和冰相过程有关。     

Fine-resolution simulation of cloud-to-ground lightning and thundercloud charge transfer

2-D 12.5 m-resolution simulations of cloud-to-ground (CG) lightning discharge processes have been performed using an improved stochastic lightning model for different types of cloud charge distributions, such as dipole, tripole, bi-dipole and multi-layer charge structures produced from the numerical simulation of thundercloud electrification. The modelling produced the fine branched channel structure of CG lightning and the results illustrate the relations between CG lightning channel propagation and cloud charge distribution. The simulated features of CG lightning are associated with the observed results. The simulation studies are essential in our understanding of complex charge transfer processes caused by CG lightning discharges in thunderclouds. The induced charges of opposite polarity are deposited or embedded in the local volumes where the bidirectional leaders passed during a CG lightning discharge. Although the embedding affects charge structure only in a pair of significant positive and negative charge regions closest to the ground, the electric field strength acutely weakens and electrostatic energy in thunderclouds is significantly consumed when the discharge terminates. In addition to simulating the upward and downward breakdown of the initial leader to ground and the ensuing return stroke (RS), the simulation assumes that current continues to flow in the channel to ground and determines the upward breakdown until the end of the discharge. For the subsequent discharge sub-process, the upward leader channel tends to transfer the charges with the same polarity as the RS, while the downward leader channel favors transfer of opposite charge to ground. In the sub-processes of a few CG flash simulations, the magnitude of the opposite charges from the downward leader exceeds that of charges with the same polarity from the upward leader so that the net charges transferred to the ground have a reversed polarity to the RS. The simulation presents similar features of CG lightning as those observed in realistic bipolar CG lightning.     

雹暴系统中单体相互作用宏微观物理过程研究

为探究雹暴过程中单体相互作用的演变特征,利用X波段双线偏振天气雷达和二维闪电监测数据,结合常规气象探空和ERA5再分析资料,分析了贵州威宁县2018年4月30日一次雹暴天气过程中单体合并特征。结果表明:本次雹暴天气主要受两单体合并影响,合并初期有“云桥”现象发生,两单体的强降水促进了连接处的增长;合并使对流系统整体加强发展,初期上升气流和下沉气流的相互作用使雷暴回波顶高降低;冰雹粒子在合并阶段呈现增长趋势,大值主要出现在合并结束前6 min和合并后6 min。本次天气过程中,负地闪频次占总地闪的94%;闪电频次在合并阶段出现跃增现象且达到峰值,较大的上升速度使得低密度霰和冰晶的增速超过高密度霰增速的5倍,低密度霰与冰晶粒子之间非感应碰撞是主要的起电过程;合并完成后,回波顶高下降,上升气流减弱,大粒子下落,受附近新生对流的影响,系统的霰粒子与冰晶粒子数短暂增加,闪电发生频次再次上升。      

基于大气层结和雷暴演变的闪电和降水关系

选取2006—2008年发生在北京及其周边地区的28次雷暴过程,基于大气不稳定度参数和雷达参量对雷暴过程进行分类,分析了不同分类条件下的总闪电活动 (SAFIR3000三维闪电定位系统观测) 和对流降水 (雷达反演) 的关系。结果表明:整体而言,总闪对应降水量的平均值为1.92×107 kg·fl-1。依据对流有效位能和抬升指数对雷暴进行分类的分析表明,较强的不稳定状态对应了较小的总闪对应降水量,同时总闪频次和对流降水量的相关性更好。基于雷达特征参数的分类分析表明,总闪对应降水量在对流运动较弱情况下最小,其次是对流运动较强的情况下,而对流运动适中时最大。     

人工触发闪电不同放电阶段电流特征关系

分析了2019年夏季在广州从化人工引雷试验场获取的14次人工触发闪电通道底部电流数据,以有无回击(RS)和初始连续电流(ICC)持续时间长短2个标准对数据进行分类,研究不同触发闪电和不同放电阶段的差异和规律。研究表明:相比无回击的触发闪电,产生回击的触发闪电具有更大的先驱放电脉冲(PCP)及初始先驱放电脉冲(IPCP)的平均峰值电流、更多的IPCP总体转移电荷量、更大的ICC平均电流和总体转移电荷量以及更长的ICC持续时间;初始连续电流持续时间是回击平均峰值电流大小、首次继后回击转移电荷量大小和首次继后回击峰值电流大小的重要影响因素,且长初始连续电流的触发闪电对应的PCP及IPCP平均峰值电流也更大、平均转移电荷量也更多;PCP和IPCP平均峰值电流与ICC持续时间相关性最强,是决定ICC放电持续时间的重要因素,未能产生初始连续电流的PCP脉冲簇其平均转移电荷量小于初始先驱放电脉冲簇,其转化的关键阈值之一是平均转移电荷量大于25.91 μC。     

一次暖云强降水主导的对流单体闪电活动特征

利用中国气象局雷电野外科学试验基地(CMA_FEBLS)三维闪电观测数据,结合广州双偏振雷达观测数据,分析了2017年5月7日广东一次暖云强降水对流单体的闪电活动及其与云降水结构的关系。该单体在4 h内产生1250个闪电,地闪比例约24%。绝大多数闪电出现在4~12 km高度,对应温度层为0℃至-40℃;闪电放电活动的峰值高度出现在8.5 km,对应环境温度约-19℃。分析的强降水单体宏观上呈现上正、中负、下正的三极性电荷结构,中部负电荷核心区约为-8℃至-15℃。在闪电活动区域中,由干雪粒子主导区域占比约82%,霰粒子主导区域占比约11%,且大部分与闪电活动关联的霰粒子主要位于4~8 km高度。总闪频数与30 dBZ雷达回波顶高、-20℃温度层上大于20 dBZ的回波体积具有较好的相关性。闪电活动的平均位置高度与20 dBZ雷达回波顶高和-20℃温度层上大于30 dBZ的回波体积具有较好的相关关系。闪电活动与最大降水强度之间具有较好的时序对应关系,单个闪电表征降水量的值为107 kg/fl量级。     

通道感应电荷对放电活动特征的影响

为探究闪电放电后电荷重置方案中异极性电荷植入法对雷暴云放电效应的影响,利用已有的三维雷暴云起放电模式,结合2011年8月12日发生在南京地区一次典型的雷暴个例,通过控制倍数改变闪电通道感应电荷量进行大量敏感性试验。模拟结果表明:闪电通道感应电荷量对空间电荷结构分布和云闪通道长度有明显影响。通道感应电荷量增加,即空间异极性电荷堆增多,加大空间电荷结构复杂程度;云闪通道在发展过程中难以穿越与自身极性相同的电荷堆,导致短通道云闪频次增加。通道感应电荷累积总量相同,不同闪电通道感应电荷量下云闪频次与通道电荷平均累积量呈负相关,即通道感应电荷平均累积量增大,云闪频次减少。而地闪频次、类型与通道感应电荷量相关性不明显。     

闪电电磁辐射中的爆发式窄脉冲序列分析

分析了发生于闪电放电过程中一类特殊放电现象\_\_爆发式窄脉冲序列。结果表明, 在30 min内测得的69例闪电放电过程中, 全部存在此类爆发式窄脉冲序列。针对6例典型闪电中包含的190例爆发式窄脉冲序列进行了详细分析, 发现窄脉冲典型宽度约为1 μs, 典型脉冲间隔4~8 μs。根据脉冲时间间隔变化和极性转换将其划分为正常型、 反向型、 对称型和反转型。负地闪和云闪产生的爆发式窄脉冲序列特征无明显差别, 而正地闪中的爆发式窄脉冲序列极性反转较为频繁。分析认为, 不同类型的RBPs可能对应流光等击穿过程在不同极性小电荷区间行进的过程。     

强风暴个例电荷结构及云闪放电差异的数值模拟

利用耦合电过程的冰粒子分档模式对长春地区两个降雹型和非降雹型强风暴个例的闪电特征进行了模拟和对比分析。结果表明,在雷暴云的初始发展期,由于上升气流较弱,两者电荷分布相似,均表现为弱的正偶极结构。随着云体不断发展,两者电荷分布开始表现出差异:降雹型个例中的上升气流较强,风切变较大,过冷水能被携带到较高的高度,冰相粒子也能被带到较高处或在较高处继续增长,使得不同区域均存在冰相粒子含量中心。因此,冰相粒子的发生范围不同、环境参数不同及荷电符号不同的非感应起电过程,形成多个电荷中心,电荷结构易出现多层分布。在不同的发展时期电荷结构均呈现出不同的形态,放电既可能在上升气流区触发,也可能在气流辐散区触发。相对而言,非降雹型个例中的上升气流较弱,风切变较小,冰相粒子的分布较规则,非感应起电过程较均匀,从而导致电荷分布始终较均匀。不同发展时期的电荷结构都相对有规则,满足放电条件的位置具有一定的相似性。     

The behavior of total lightning activity in severe Florida thunderstorms

The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier results for thunderstorm microbursts, the peak flash rate precedes the severe weather at the ground by 5–20 min. A distinguishing feature of severe storms is the presence of lightning ‘jumps' — abrupt increases in flash rate in advance of the maximum rate for the storm. The systematic total lightning precursor to severe weather of all kinds — wind, hail, tornadoes — is interpreted in terms of the updraft that sows the seeds aloft for severe weather at the surface and simultaneously stimulates the ice microphysics that drives the intracloud lightning activity.     

北京地区雷暴过程闪电与地面降水的相关关系

该文选取北京地区2006年夏季的18次雷暴过程,利用SAFIR3000三维闪电定位系统观测到的总闪数据,分析了闪电与雷达反演的对流活动区降水量和对流活动区面积的相关关系,结果表明:北京地区的雷暴活动中,单个闪电所表征的降水量的范围在0.86×10~7～6.57×10~7kg/fl之间,平均值为2.65×10~7kg/fl;闪电活动与对流活动区降水量的线性相关关系显著,相关系数达到0.826;闪电活动与对流活动区面积也具有显著的线性关系,相关性系数达到0.846。文中给出了基于6 min闪电频次估算6 min对流降水量以及对流活动区面积的拟合方程。分析还发现,总闪活动与降水的关系要明显好于地闪,总闪信息的应用极大提高了分析结果的质量和可信性,分析结果对于利用闪电信息估测降水具有参考意义。     

Semi-idealized modeling of lightning initiation related to vertical air motion and cloud microphysics

A three-dimensional charge–discharge numerical model is used, in a semi-idealized mode, to simulate a thunder-storm cell. Characteristics of the graupel microphysics and vertical air motion associated with the lightning initiation are revealed, which could be useful in retrieving charge strength during lightning when no charge–discharge model is available. The results show that the vertical air motion at the lightning initiation sites (W_ini) has a cubic polynomial correlation with the maximum updraft of the storm cell (W_cell-max), with the adjusted regression coefficient R² of approximately 0.97. Meanwhile, the graupel mixing ratio at the lightning initiation sites (q_g-ini) has a linear correlation with the maximum graupel mixing ratio of the storm cell (q_g-cell-max) and the initiation height (z_ini), with the coefficients being 0.86 and 0.85, respectively. These linear correlations are more significant during the middle and late stages of lightning activity. A zero-charge zone, namely, the area with very low net charge density between the main positive and negative charge layers, appears above the area of q_g-cell-max and below the upper edge of the graupel region, and is found to be an important area for lightning initiation. Inside the zero-charge zone, large electric intensity forms, and the ratio of q_ice (ice crystal mixing ratio) to q_g (graupel mixing ratio) illustrates an exponential relationship to q_g-ini. These relationships provide valuable clues to more accurately locating the high-risk area of lightning initiation in thunderstorms when only dual-polarization radar data or outputs from numerical models without charging/discharging schemes are available. The results can also help understand the environmental conditions at lightning initiation sites.