Climatology of lightning activity in South China and its relationships to precipitation and convective available potential energy

This study examined lightning activity and its relationship to precipitation and convective available potential energy(CAPE) in South China during 2001–12, based on data from the Guangdong Lightning Location System, the Tropical Rainfall Measuring Mission satellite, and the ERA-Interim dataset. Two areas of high lightning density are identified: one over the Pearl River Delta, and the other to the north of Leizhou Peninsula. Large peak-current cloud-to-ground(LPCCG) lightning(75 kA) shows weaker land–offshore contrasts than total CG lightning, in which negative cloud-to-ground(NCG) lightning occurs more prominently than positive cloud-to-ground(PCG) lightning on land. While the frequency of total CG lightning shows a main peak in June and a second peak in August, the LPCCG lightning over land shows only a single peak in June.The ratio of positive LPCCG to total lightning is significantly greater during February–April than during other times of the year. Diurnally, CG lightning over land shows only one peak in the afternoon, whereas CG lightning offshore shows morning and afternoon peaks. The rain yield per flash is on the order of 10~7–10~8kg per flash across the analysis region, and its spatial distribution is opposite to that of lightning density. Our data show that lightning activity over land is more sensitive than that over offshore waters to CAPE. The relationships between lightning activity and both precipitation and CAPE are associated with convection activity in the analysis region.     

雷暴闪电活动特征研究进展

从一般雷暴、灾害性雷暴和台风的闪电活动特征以及雷暴闪电尺度特征四个方面对相关研究进行梳理.一般雷暴通常具有正常极性电荷结构,云/地闪比例在3左右(中纬度地区),地闪中正地闪占比为10％左右,负地闪位置往往更集中于对流区.灾害性雷暴倾向具有活跃的云闪,低比例的地闪,易出现反极性电荷结构,正地闪比例偏高.闪电活动与灾害性天...     

青藏高原闪电与NO_2的分析及中国内陆地区LNO_x产量的估算

为了进一步认识闪电活动与对流层氮氧化物的关系及更准确地估算中国地区闪电产生的氮氧化物(LNOx)总量,选取人口稀疏,工业生产水平较低的青藏高原地区作为研究区域,基于LIS(Lightning Imaging Sensor)和GOME-2(The Global Ozone Monitoring Experiment-2)卫星探测仪资料,分析了青藏高原中部区域2009年1月至2012年2月闪电与对流层NO2垂直浓度(VCD)月均值资料的时空分布特性和相关性。在此基础上,结合Beirle et al.(2004)的LNOx估算方法,估算了中国内陆地区的LNOx产量。结果表明:青藏高原地区对流层NO2与闪电与在年际趋势、空间分布及季节变化上保持很好的一致性,闪电密度与NO2VCD的线性拟合相关系数为0.84,这表明青藏高原地区NOx受人为源影响小,是研究LNOx的理想区域。基于拟合结果,估算得到中国内陆地区LNOx的年均产量为0.15(0.03~0.38)Tg(N)a-1。这一结论进一步缩小了以往研究中中国地区LNOx产量估算的不确定范围,有助于更清楚地认识闪电在中国气候变化中的重要作用。     

一次特大暴雨过程三维和二维系统闪电特征对比分析

利用三维(ADTD-2C)和二维(ADTD)闪电定位系统资料, 对比分析了湖北省一次特大暴雨过程中两套系统闪电活动特征, 得出以下结论: (1)本次过程中地闪多于云闪, 二者均以负极性为主。(2)三维系统正地闪在地闪中的占比低于正云闪在云闪中的占比, 高于二维系统正地闪在地闪中的占比。(3)三维系统雷电流幅值集中分布在0~30 kA, 较二维系统(10~50 kA)更集中, 三维系统的雷电流累积概率较湖北省多年统计结果明显偏小, 二维系统的雷电流累积概率略高于统计值。(4)两套系统总地闪和负地闪活跃时段基本一致。(5)两套闪电定位系统地闪密集区基本一致, 且和云闪密集区基本重合, 闪电分布集中程度高, 主要分布在槽前正涡度平流区。三维系统地闪密度大于二维系统, 最大值分别为5.78 fl/(km2·d)和2.39 fl/(km2·d)。三维系统中正、负闪电交错分布, 二维系统中正、负地闪局部存在空间分离现象。(6)云闪密度大小与二维地闪相当、水平分布特征与三维地闪一致。垂直方向上, 云闪主要发生在10 km以下, 其中2~4 km云闪分布密集, 占总云闪的47.24%。      

The Characteristics of Cloud-to-Ground Lightning Activity with Severe Thunderstorm Wind in South and North China

The characteristics of cloud-to-ground（CG） lightning activity with severe thunderstorm wind（STW） in South and North China are analyzed using CG lightning data, radar data, and serious weather reports. The percentage of positive CG（PCG） flashes with STW in North China is larger than that in South China. STW takes place during the period when the total CG and PCG density is increasing fastest. STW also occurs close to the high-value center of CG and PCG density. In North China, the CG and PCG density in the grid of STW maximizes approximately 20 minutes after the STW occurs; while in South China, the PCG density and percentage of PCG in the grid of STW maximizes about 10 minutes before the occurrence of STW. The high-value centers of CG density and PCG density in North China move slightly faster than those in South China, which is opposite to the rate of increasing CG activity.     

北京城区相继多次降雹的一次强雷暴的闪电特征

受东北冷涡和低层暖湿气流影响,2016年6月10日北京午后爆发了相继5次降冰雹的一次强雷暴天气过程。利用国家“973”项目“雷电重大灾害天气系统的动力—微物理—电过程和成灾机理（雷暴973）”2016年夏季协同观测期间获得的闪电全闪三维定位和多普勒天气雷达等资料,详细分析了此次雹暴的闪电活动和雷达回波特征。此次雹暴过程包括三个孤立的单体相继发展、并合,所分析的4次降雹过程中,总闪电频数在降雹期间都有明显增多,最高可达179 flashes min?1。云闪占全部闪电的80%以上,其中3次降雹前出现正地闪突增,其比例升高,占全部地闪的比例最高达58%。降雹时雷达回波>45 dBZ的面积增大,顶高超过13 km。整个雹暴过程,闪电辐射源主要分布在6～10 km的高度区域,与强回波具有一致性。所分析的4次降雹过程均出现明显的总闪频数跃增,并通过2σ阈值检验,其中3次提前时间为8～18 min,说明总闪频数对于降雹过程有一定的预警能力。     

北京多频段闪电三维定位网及一次雷暴过程的闪电时空演化特征

北京多频段闪电三维定位网（Beijing Broadband Lightning NETwork,简称BLNET）是一个研究和业务相结合的区域性全闪三维定位网。2015年,对BLNET硬件、站网布局及定位算法等方面进行了更新升级,提高了传感器的灵敏度,提升了软件的运算效率和站网的探测性能。升级后的BLNET不仅具备了对云闪、地闪脉冲类型的快速识别和电流峰值估算等功能,也实现了对闪电辐射源脉冲的三维实时定位,以及通道可分辨的闪电放电过程精细定位。对2017年7月7日一次雷暴过程的闪电辐射源脉冲实时三维定位结果分析表明,这次雷暴过程一共观测到11902次闪电,以云闪为主,地闪占总闪的28%,正地闪较少,仅占总地闪的5%,在雷暴成熟期,最大闪电频数高达927 flashes (6 min)?1。通过对比分析闪电辐射源位置和对应时刻的雷达回波,发现辐射源基本集中在强回波范围内。对一次正地闪的精细定位表明,该正地闪初始阶段表现出明显的预击穿过程,闪电辐射源的始发位置位于海拔高度约5.4 km,随后通道向上发展,在约10 km高度,通道开始沿着水平发展。对一次负地闪的精细定位表明,初始阶段放电首先从约7.1 km高度处始发,通道向南水平发展,同时部分负先导分支向下发展,约38 ms后,通道短暂停止发展,17 ms后,通道始发处重新激发。以上结果表明,BLNET不仅具备对整个雷暴生命史闪电活动的三维实时定位和监测,而且可以实现对闪电三维放电通道的精细定位。     

Study of the total lightning activity in a hailstorm

A thunderstorm that developed over northeastern Spain on 16 June 2006 is analyzed. This severe thunderstorm produced hailstones as large as 40 mm and had a lifetime of 3 h and 30 min. Radar cross-sections show strong vertical development with cloud echo tops reaching an altitude of 13 km. The specific characteristics of the lightning activity of this storm were: (i) a large amount (81%) of negative cloud-to-ground (−CG) flashes with very low peak currents (< 10 kA in absolute value), (ii) a very large proportion of intra-cloud (IC) flashes with an IC/CG ratio reaching about 400, (iii) a large number of “short” IC flashes (with only 1-VHF source according to SAFIR detection), (iv) a large increase of the −CG flash rate and of the CG proportion near the end of the storm. The rate of −CG flashes with a low peak current were observed to evolve similarly to the rates of IC flashes. Most of them have been assumed to be IC flashes misclassified by the Spanish Lightning Detection Network (SLDN). They have been filtered as it is usually done for misclassified +CG flashes. After this filtering, CG flash rates remained very low (< 1 min^− 1) with +CG flashes sometimes dominant. All the particular lightning activity characteristics similar to those observed in the Severe Thunderstorm Electrification and Precipitation Study (STEPS) campaigns support the hypothesis that this thunderstorm could have had an inverted-polarity or complex charge structure. The maximum IC flash rate (67 min^− 1) peaked 24 min before the presence of reflectivity higher than 60 dBZ. The IC activity abruptly decreased during the period when reflectivity was dramatically increasing. The time of maximum reflectivity observed by radar was consistent with the times of reported hail at the ground.     

Transient currents in the global electric circuit due to cloud-to-ground and intracloud lightning

Intracloud (IC) and cloud-to-ground (CG) lightning flashes produce transient changes in the electric field (E) above a thundercloud which drive transient currents in the global electric circuit (GEC). Using in-cloud and above-cloud E data from balloons, ground-based E data, and Lightning Mapping Array data, the above-cloud charge transfers due to lightning transients are estimated for five IC and five CG flashes from four thunderstorms that occurred above the mountains in New Mexico, USA, in 1999. For the five CG flashes (which transferred − 4 to − 13 C to the ground), the transient currents moved + 1 to + 5 C of charge upward from cloudtop toward the ionosphere, with an average transient charge transfer of about 35% of the charge transferred to ground. For the five IC flashes (which neutralized 6 to 21 C inside the cloud), the transient currents moved − 0.7 to − 3 C upward, with an average transient charge transfer of about 12% of the lightning charge. Estimates for three thunderstorms indicate that the transient currents made only a small GEC contribution compared to the quasi-stationary Wilson currents because of the offsetting effects of IC and CG flashes in these storms. However, storms with extreme characteristics, such as high flash rates or predominance of one flash type, may make a significant GEC contribution via lightning transients.     

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。     

北京地区闪电特征初探

对信息产业部第22所研制的XDD03A雷电探测系统获取的2000～2003年北京地区云-地闪电资料进行了闪电的日变化、月变化、闪电的强度、闪电密度、极性等方面的分析,研究了北京地区的闪电分布特征。结果表明：云地闪中负闪占大多数;正闪的平均强度大于负闪;闪电的发生有明显的日变化,呈双锋双谷形式;最多闪电日数出现在7月和8月,几乎每天都出现闪电,而闪电次数最多则出现于8月份。北京地区闪电分布主要集中于4个区域,闪电的空间分布与地形及下垫面的性质有关。     

一次具有对流合并现象的强飑线系统的闪电活动特征及其与动力场的关系

受东北冷涡与副热带高压西北部暖湿气流影响,2015年7月27日北京地区爆发了一次具有明显对流单体合并特征的强飑线灾害性强对流天气过程。利用北京闪电定位网（BLNet）总闪定位、多普勒雷达和探空资料等,详细分析了此次飑线过程整个生命史期间不同对流区的总闪活动特征。结果表明,整个飑线过程以云闪为主,地闪活动以负地闪为主;对流单体合并时云闪数量激增,飑线过程后期正地闪比例跃增。93%的闪电主要分布在距对流线10 km范围内,层云区闪电较少;层云区的闪电电荷来源主要是由对流区的电荷经过过渡区输送而来,正地闪更易发生在过渡区和层云区。对流合并过程中有大量的水汽集中,垂直积分液态含水量（VIL）峰值超前闪电峰值24 min。利用变分多普勒雷达分析系统（VDRAS）对这次过程的三维风场进了反演,据此对单体合并期间闪电增强的动力原因进行了研究。根据VDRAS反演的动力场来看,对流云单体合并主要发生在低层辐合区内,合并后上升运动加强,上升气流范围变大,闪电活动显著增强,并主要发生在具有较强垂直风切变的区域,少部分闪电发生在对流区后部开始出现下沉气流的区域。     

山东地区闪电的特征分析

利用1998～2000年山东地区雷电探测网获取的云对地闪电资料，从闪电的日变化、闪电的强度、闪电密度、极性等方面研究了山东地区的雷电分布特征。结果表明，云地闪电中负闪占绝大多数；正闪的平均强度大于负闪，在闪电强度较小和较大时发生的正闪占总正闪电总数的比例相应地高于负闪；闪电的发生也有明显的日变化，总体呈双峰双谷形式；闪电的空间分布与地形有关，也与下垫面的性质有关。对部分城市市区闪电密度的统计分析表明，济宁、莱芜、滨州、泰安、济南等位于鲁中地区的城市更应加强人工防雷工作。     

华北一次中尺度对流系统中的闪电活动特征及其与雷暴动力过程的关系研究

利用地面地闪定位资料、多普勒天气雷达和常规气象资料, 分析了一次具有前部对流线和后部大范围层状云降水(LLTS)的典型中尺度对流系统(MCS)的闪电活动演变特征。整个MCS生命史中负地闪占主导地位, 正地闪则表现不活跃。观测得到MCS消散阶段云闪与地闪的比例为2∶1, 地闪主要分布在地面相对位温和对流不稳定能量均达到高值的区域; 负地闪主要密集地分布在大于40 dBZ的回波范围内; 正地闪则稀疏地分布在30～40 dBZ的回波范围内。在低于-40℃的温度区域内地闪分布较多, 而密集的地闪分布在温度梯度大的区域内。结合单多普勒雷达的水平风场反演, 发现地闪集中出现在气流表现为气旋性切变或水平风呈现切变的区域。该区域与MCS的强回波区相对应, 并且地闪易发生在上升气流达到最大并开始出现下沉气流的阶段。     

OBSERVATION AND MODEL ANALYSES OF POSITIVE CLOUD-TO-GROUND LIGHTNING IN MESOSCALE CONVECTIVE SYSTEMS*

The analyses of spatial and temporal characteristics of positive cloud-to-ground(CG) lightning for four mesoscale convective systems and two severe local convective systems in 1989 and 1990 show that positive CG flash rate usually has two peak values.The major peak occurs during the developing stage of the storm and most of the positive CG flashes originate at the lower part of the storm.The minor occurs during the dissipative stage of the storm and most of the positive CG flashes originate at the upper part of the storm,especially in the region of the wind divergence in the storm anvil.The positive CG flash rate is almost an order of magnitude larger in the developing stage than in the dissipative stage.The appearing time of the peak of negative CG flash rate is in accordance with that of the valley of positive CG flash rate.The higher the intensity of the radar echo,the higher the positive CG flash rate.Most of the positive CG flashes occur when the weak echo area is larger,and mostly originate in the region where the radar echo intensity is about 10dBz and in the back region of the moving storms.The spatial distribution of the positive CG flashes is much more dispersive than that of the negative.The mesoscale analysis reveals a bipolar lightning pattern.The mean bipole-length reaches its minimum during the mature stage of the storm and reaches the maximum during the developing stage of the storm.The vertical distribution of the charge density is calculated by a one-dimensional charging model.Then,we discuss the producing condition of the positive CG lightning and forming cause of charge structure mentioned above.     

一次飑线过程的闪电活动特征

结合地闪定位资料和TRMM卫星LIS观测的总闪电资料对一次飑线过程闪电活动进行分析,结果如下:这次飑线过程的正地闪超过了负地闪,占地闪的54.7%.在系统发展的初始阶段全部为正地闪;在系统的快速发展阶段地闪频数明显增大,正地闪比例很高,均在75%以上.在系统成熟至减弱阶段,地闪频数开始下降,而正地闪比例下降,负地闪的比例却越来越大,并占据支配地位.正地闪发生在线对流区(即强回波区内或附近),负地闪发生在层状云区.正地闪并不对应于主上升气流区而是紧邻上升气流区的后部.该雷暴云内闪电活动非常频繁,云地闪比例高达26.1:1.降雹和地面大风区位于正地闪密集区内,地闪频数峰值对应于地面大风阶段.     

Evaluation of LPATS data using VHF interferometric observations of lightning flashes during the Eulinox experiment

During the Eulinox (European Lightning Nitrogen Oxides Project) campaign, two lightning sensors were available: a Lightning Position and Tracking System (LPATS), and the ONERA VHF interferometric (ITF) mapper. We looked for the typical VHF signature of positive and negative cloud-to-ground flashes in ITF records in order to separate intra-cloud (IC) flashes from cloud-to-ground (CG) flashes during five periods from 2 days. Then we used this set of data to check the efficiency of the South Germany LPATS. We concluded that this LPATS detected nearly all the negative CG flashes, but one-fourth of LPATS negative strokes are in fact IC flashes. The ratio of misinterpretation is much smaller (15%) for multi-stroke negative CG flashes. The LPATS recorded 62% of the positive strokes, but only 43% with the right polarity, and only 25% of LPATS positive strokes actually belonged to a positive CG flash. This reliability ratio is 100% if we consider only high-intensity LPATS strokes.     

A Comparison of the Characteristics of Total and Cloud-to-Ground Lightning Activities in Hailstorms

The region of Beijing-Tianjin-Hebei is covered by two different lightning detection networks: SAFIR (Systeme d’Alerte Fondre par Interferometrie Radioelecctrique) for total lightning, including IntraCloud (IC) flashes and Cloud-to-Ground (CG) flashes, and the ADTD (ADvanced TOA and Direction system; TOA denotes time of arrival) network of China for CG lightning. Fourteen isolated hail-bearing thunderstorms in this region were examined in this study, using the data of SAFIR and ADTD. The peak of lightning frequency, for both total lightning and CG lightning, was often observed in advance of the occurrence of hailstones on the ground, with a trend of a rapid increase of lightning frequency before the hail was reported. The average lead times of the two types of lightning jump before hail events were obtained (total lightning: 32.2 min; CG: 25.4 min) through the 2σ lightning jump algorithm. Additionally, in hailstorms with a high ratio of positive CG flashes, the diameter of hail was larger and the duration of hail was longer; when negative CG flashes dominated, the diameter of hail was relatively small. The comparison of the characteristics of total lightning and CG flashes in hailstorms in this study is expected to serve as a supplementary tool for hail forecasting.     

一次中尺度雷暴大风过程的闪电特征分析

2005年6月21日山东北部出现了一次中尺度对流系统,并伴有地面灾害性大风。作者综合闪电定位资料、雷达和卫星资料详细分析了这次中尺度对流系统的闪电活动特征,结果表明,在系统初始发展阶段地闪频数快速增加.成熟阶段地闪频数一直较高,且都在20次/5 min以上,在减弱消散阶段,正地闪比例超过负地闪。负地闪多发生在对流降水区,而正地闪则对应于稳定的层状云降水区。逐小时地闪次数峰值滞后于云顶最低温度峰值,小于-50℃的冷云覆盖面积峰值滞后于地闪次数峰值。这次地面大风主要是较强下沉气流底部外流造成的,利用WINDEX计算的地面最大风速潜势与观测的阵风值非常接近。地面大风阶段对应着剧烈的闪电活动,地闪频数的跃增略提前于地面强风发生时间,这对灾害性天气过程的监测预警具有一定的参考价值。     

OBSERVATION AND MODEL ANALYSES OF POSITIVE CLOUD-TO-GROUND LIGHTNING IN MESOSCALE CONVECTIVE SYSTEMS

The analyses of spatial and temporal characteristics of positive cloud-to-ground(CG)lightning for four mesoscaleconvective systems and two severe local convective systems in 1989 and 1990 show that positive CG flash rate usuallyhas two peak values.The major peak occurs during the developing stage of the storm and most of the positive CGflashes originate at the lower part of the storm.The minor occurs during the dissipative stage of the storm and most ofthe positive CG flashes originate at the upper part of the storm,especially in the region of the wind divergence in thestorm anvil.The positive CG flash rate is almost an order of magnitude larger in the developing stage than in thedissipative stage.The appearing time of the peak of negative CG flash rate is in accordance with that of the valley of pos-itive CG flash rate.The higher the intensity of the radar echo,the higher the positive CG flash rate.Most of the positive CG flashes oc-cur when the weak echo area is larger,and mostly originate in the region where the radar echo intensity is about 10dBzand in the back region of the moving storms.The spatial distribution of the positive CG flashes is much more dispersivethan that of the negative.The mesoscale analysis reveals a bipolar lightning pattern.The mean bipole--length reaches itsminimum during the mature stage of the storm and reaches the maximum during the developing stage of the storm.The vertical distribution of the charge density is calculated by a one-dimensional charging model.Then,we discussthe producing condition of the positive CG lightning and forming cause of charge structure mentioned above.