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1.
《中国科学:地球科学》2016,(5)
为了进一步认识强雷暴中正地闪偏多的原因,本文利用三维雷暴云动力-电耦合数值模式,通过模拟一次强雷暴过程,讨论了正地闪频发需要的条件.结果表明,云闪的发生需要较强的上升气流,而正地闪的发生不仅需要更强的上升气流,还需要云低层存在强的下沉气流,即正地闪发生在强雷暴云成熟阶段后期,对应固态降水强度最大时段.此时,云内主上升气流区内的各电荷区被强上升气流抬升,短暂地呈现反三极性结构,非感应起电机制作用使大量的霰粒子带正电荷,形成了中部电荷密度较大、范围较深厚的正电荷区.而下沉气流区比上升气流区电荷结构更复杂,呈正、负交替的多层结构.由于雷暴云上部负电荷区中部分带负电荷的霰和雹粒子被下沉气流输送到低层,及低层区域感应起电机制的共同作用,使上升气流区外围的对流降水区中的霰和雹粒带上负电荷,在近地面形成一个较强的、范围较大的负电荷区.强雷暴云中下部存在的这个偶极性电荷结构为正地闪的发生提供了有利条件.正地闪发生阶段对应着上升气流、雹粒子体积和总闪的快速增强阶段.因此,强雷暴中正地闪的发生可作为雷暴强度及冰雹形成的一个指示因子. 相似文献
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本研究利用加入起电、放电参数化方案的数值模式（Weather Research and Forecasting Model（Version 3.7.1）,WRF3.7.1_ELEC）,通过设计五组不同非感应起电及感应起电参数化方案敏感性试验,对发生在青藏高原东北部青海大通地区的一次雷暴过程进行模拟研究,对比分析了不同非感应起电机制及感应起电机制对雷暴云电荷结构的影响.结果表明：在雷暴云发展旺盛阶段,Saunders（S91）、Riming Rate（RR）、和Saunders和Peck（SP98）三种非感应起电方案模拟的雷暴云最低层均为负电荷区,而混合方案（Brooks and SP98,BSP）模拟的雷暴云最低层为正电荷区,主电荷区自下而上为"+-+-"排列的四层电荷结构.与甚高频辐射源定位法推算的结果对比,BSP方案模拟的本次高原雷暴云电荷结构更接近实际情况;几种不同非感应起电方案模拟的主电荷区外围与主电荷区电荷结构不同,说明在雷暴发展的不同阶段雷暴云的电荷结构是不同的;几种非感应起电方案模拟的电荷结构不尽相同,主要是由于霰、冰和雪粒子在不同高度所带电荷的极性及电量的大小不同,霰粒子的电荷密度对低层的影响较大,冰粒子和雪粒子的电荷密度对中上层的影响较大;加入感应起电机制后,雷暴云电荷结构分布几乎没有变化,但能使雷暴云发展旺盛阶段低层和中层的正负电荷区电荷密度有所加强. 相似文献
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本文自主研制性能稳定的双金属球三维电场探空仪,并结合气象探空仪等构建了雷暴电场-气象综合探空系统,实现了雷暴云内三维电场及温度、湿度的同步测量.2019年夏季对华北平原地区雷暴开展穿云观测,并结合地面大气电场、雷达回波、变分多普勒雷达分析系统(VDRAS)反演的动力场等资料进行综合研究,首次给出该地区雷暴云内的电场和电荷结构分布特征.对2019年8月7日发生的一次中尺度对流系统电场探空发现,在雷暴减弱阶段,其弱回波区内存在5个极性交替的电荷区:4.4~5.6 km之间的上部正电荷区(0℃附近)、3.6~4.4 km之间的中部负电荷区和1.0~3.6 km之间的下部正电荷区,此外在1 km下方有一个负极性电荷区,雷暴云顶附近5.7~6.9 km之间为一个弱负极性屏蔽电荷区.其中,中部负电荷区和下部正电荷区由多个不同强度、不同厚度的电荷层构成.此外,电场探空系统在中部负电荷区高度范围内经历的上升—下沉—再次上升的往返探空数据表明,雷暴云内动力环境复杂,电荷结构分布相似但又有所差异,反映了实际雷暴云内电荷分布的时空不均匀性和复杂性. 相似文献
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《中国科学:地球科学》2016,(7)
上行地闪是一种始发于超高建筑物(高度至少在100m以上)顶端的大气放电现象,目前对其的认知主要通过地面观测,而相应的理论模式研究较为缺乏.本文在已有的双向先导随机模型的基础上,创建上行地闪随机放电参数化方案,并耦合到雷暴云起、放电模式中,进行了二维高分辨率上行地闪放电的模拟实验,得到的上行闪电与观测结果具有较好的一致性.通过分析雷暴云电荷结构给出了常规地闪起始的有利云内环境特征,并分析了正、负上行地闪一些特征的异同,结果表明:模拟得到的上行正地闪多为诱导触发的上行地闪,通常是三极电荷结构下次正电荷区与地面之间的一种放电现象,前次云闪过程对空间环境电场的影响为其起始提供了有利条件,整个放电过程延伸范围有限、分叉少、放电不充分;上行负地闪多为偶极电荷结构中主负电荷区与地面之间的放电过程,温度层结的高度低以及降水粒子的下沉使电荷区高度降低是其起始的根本原因,上行负地闪发展旺盛,分支较多;诱导触发的上行地闪主要发生于雷暴成熟期,而自行触发的上行地闪则更容易在雷暴消散期起始. 相似文献
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2016年夏季在青海大通地区获得一次局地雷暴云内的电场探空资料,结合雷达、地闪定位资料,详细分析了该雷暴的地闪活动特征及云内的电荷结构.结果显示,该雷暴过程的负地闪在时间上呈间歇性发生,在空间分布上表现为不连续,且所有的正地闪都发生于雷暴的成熟阶段.在雷暴成熟阶段与消散阶段过渡期获得云内的垂直电场廓线表明,雷暴内的电荷结构在探空阶段呈四极性,最下部为处于暖云区内负电荷区,往上依次改变极性.最上部的正电荷区由于数据丢失无法判断其上边界外,其余3个电荷区的海拔高度分别为:5.5～5.7km(3.4～2.3℃)、5.7～6.2km(2.3～-0.4℃)和6.2～6.6km(-0.9～-1.7℃),对应的电荷密度为-1.81nC·m-3、2.47nC·m-3和-1.76nC·m-3.其中,下部正电荷区的强度最大,其次为上部的负电荷区.通过分析电荷区分布与正地闪活动的关系,认为暖云区内负电荷区的形成有利于诱发下部正电荷区的对地放电. 相似文献
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雷暴云内闪电双层、分枝结构的数值模拟 总被引：2，自引：0，他引：2
试验了一种逃逸启动、双向随机发展的放电参数化改进方案, 并进行了12.5 m的高分辨率、二维雷暴云数值模拟试验, 模拟再现的雷暴云内闪电特征在通道扩展范围和双层、分枝结构以及与位势阱位置的相互配合等方面与实际VHF源定位观测资料分析结果是一致的. 进一步发现: (1) 闪电在雷暴云内相邻的正、负电荷区边界附近触发后, 负先导向正电荷区发展、正先导向负电荷区发展. 存在正负两种极性的云闪, 他们的极性由云中相邻正、负电荷累积区位置的上下配置决定. (2) 电荷累积区的空间分布制约着闪电的空间范围. 云闪几乎遍及其所传播的电荷堆, 遭遇到局域性、与通道极性相同的电荷堆时, 通道将转向、绕开该电荷堆. (3) 电位的空间分布形态同样制约着闪电通道传播方向和几何结构: 先导通道进入正或负位势阱之前沿着最大电位梯度方向传播; 当先导通道穿过它们的中心之后通道更趋于电位变化缓慢的地方发展. (4) 云闪通道在穿过电荷累积区中心以前, 有较好的分形特征, 幂指数约为1.45; 而其后向低电荷浓度地区延伸时, 幂指数随着半径增加而减小. (5) 放电结束后通道感应生成的异极性电荷沉积在正、负先导通道经过的区域, 形成新的、复杂的云内电荷空间分布, 位势极值可由200下降到20 MV. 相似文献
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基于三亚(109.6°E,18.4°N)VHF电离层相干散射雷达观测,分析了我国低纬电离层E区场向不规则结构连续性回波的发生特征.研究结果表明:白天,E区连续性回波的多普勒速度范围为-50至25m/s,多普勒宽度主要分布在20至70m/s;连续性回波的高度大约以1km/h的速度缓慢下降,与偶发E层(Es)底部所在高度(hbEs)有很好的相关性,表明在背景电场影响下,Es经梯度漂移不稳定性产生场向不规则结构,引起E区连续性回波.夜间,E区连续性回波的多普勒速度范围为-50至50m/s,多普勒宽度为20至110m/s,回波在时间-高度-强度图上常呈现多层结构,可能与潮汐引起的多个离子层相关;而E区连续性回波的短暂中断,以及120km以上高E区连续性回波的发生,则可能归因于赤道扩展F极化电场的影响.此外,对E区连续性回波多普勒速度与全天空流星雷达风场观测的比较发现,在100km以下,多普勒速度与子午风场有很好的相关性. 相似文献
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中低纬电离层E区不规则体准周期雷达回波现象,在地球不同经度区被观测到并开展了有关研究.本文利用三亚(109.6°E,18.4°N)VHF相干散射雷达2011年2月6日的观测,第一次给出了中国低纬电离层E区准周期回波的发生和变化特征.观测结果表明:准周期回波发生在地方时夜间2100—2200LT的110km高度上,与连续性回波可同时发生;准周期回波斜纹在雷达探测的高度-时间-强度(HTI)图上可延伸5～20km,持续时间为5～15min,回波斜纹高度随时间以20～30m/s下降,斜纹在HTI图上彼此间隔10km和10min左右.此外,雷达回波多普勒谱和雷达干涉分析显示不同高度准周期回波的多普勒速度随高度-时间表现出不同的变化趋势,与回波条纹斜率无明显联系,不同高度准周期回波对应的不规则体在东西方向也表现出截然不同的运动特征.分析结果表明,三亚电离层E区准周期回波的发生可能并不是由散块Es随着中性风周期性的经过雷达探测区域所致,而可能和Es中的扰动结构相关. 相似文献
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雷暴云底部正电荷区对闪电类型影响的数值模拟 总被引：2，自引：0，他引：2
在经典的雷暴云三极电荷结构的假定下结合已有的随机放电参数化方案,进行了二维高分辨率闪电放电的模拟实验,定量的探讨了雷暴云底部正电荷对闪电类型的影响．结果表明：（1）雷暴云底部正电荷对负地闪和反极性云闪的产生起了关键作用,随着底部正电荷区的电荷密度大小或分布范围的增大,闪电类型依次从正极性云闪向负地闪再向反极性云闪变化;（2）相对于电荷区分布范围而言,底部正电荷区的电荷密度大小对闪电类型的影响起主导作用．只有当雷暴云底部正电荷区的最大电荷密度取值在一定范围内时,才会出现负地闪,并且负地闪的发生概率相对固定;（3）在该范围内,负地闪的发生由底部正电荷区的电荷密度大小以及分布范围共同决定,且其与云闪触发条件之间存在一个线性边界;（4）底部正电荷区的电荷密度大小以及分布范围的共同效果是改变底部正位势阱的分布,当闪电启动参考电位接近0MV时生成反极性云闪,而当其远小于0MV时则更容易形成负地闪． 相似文献
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ZHAGN Yijun DONG Wansheng ZHAO Yang ZHANG Guangshu Zhang Hongfa CHEN Chengpin ZHANG Tong 《中国科学D辑(英文版)》2004,47(Z1)
The comprehensive observations on lightning discharges were conducted in Naqu area of Qinghai-Tibet Plateau in summer of 2002. The electric structures of thunderstorms and the characteristics of lightning discharges at initial stage were analyzed by using the observation data. The results show that most of intracloud (IC) lightning flashes were polarities inverted in thunderstorms with tripole electric charge structure and occurred between negative charge region located in the middle of the thunderstorm and positive charge region located at the bottom of the thunderstorm. The radiation characteristics of discharge processes in cloud with longer lasting time involved in Cloud-to-Ground (CG) lightning flashes were similar to that of IC discharges.A lot of radiation pulses were produced in these discharge processes. Because the IC discharges took place at the bottom of thundercloud and were near the ground, they may produce more serious damage to equipment on the ground therefore should not be neglected in lightning protection. 相似文献
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本文利用已有的随机放电参数化方案,结合四次探空资料,进行了12.5 m的高分辨率二维雷暴云数值模拟实验,得到了各种雷暴云电荷结构下的地闪个例,并就地闪击地点与空间电荷、电位分布之间的相互关系进行了分析.结果表明:(1)由空间电荷唯一确定的电位分布决定了先导的传播最大趋势,而闪电传播的随机性所带来的地闪击地点的不确定范围被限制在3 km之内,利用动态聚类法迭代得出的三个击地点位置之间的差为1 km左右.(2)负地闪的初始点与击地点的位置差主要分布在0~6 km范围内,且93%的负地闪分布在0~4 km范围内,正地闪的分布相对较广,0~3 km范围内占48%,3~6 km范围内占34%,6~10 km范围内占18%.(3)正、负地闪主要产生于离地面最近的一对电荷堆之间,其起始高度越高,初始点与击地点位置差分布越广;另外,产生于三级性雷暴云电荷结构下的正地闪,其起始于上部的主正电荷堆与中部主负电荷堆之间,由于下行正先导会绕过底部的次正电荷堆,因此其击地点与初始点的距离基本在6 km以上. 相似文献
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FengXia Guo Yang Li ZhaoChu Huang ManFei Wang FanHui Zeng ChunHao Lian YiJun Mu 《中国科学:地球科学(英文版)》2017,60(12):2204-2213
Based on the Weather Research Forecasting (WRF) model that features charging and discharging parameterization, relationships between tornado, hail and lightning were investigated for a tornado-producing (EF4 intensity) supercell thunderstorm over Yancheng City in Jiangsu Province, China, on 23 June 2016. Based on a sounding at 0800, there was a low lifting condensation level, substantial convective available potential energy (CAPE), and strong vertical wind shear near Yancheng City, which promote supercell development. At 1400, observations revealed that hail production and a dramatic increase of positive cloud-to-ground flash rates occurred simultaneously, maximizing five minutes later. The tornado occurred 30 min after the hail production. The time of minimum positive cloud-to-ground flash rates was 15 min later. The simulation indicated that the tornadic supercell moved eastward and that positive cloud-to-ground flash rates increased dramatically at 1400, the same as observed, but their maximum was 5 min later than observed. The simulated updraft volume peaked at 1425 and the simulated downdraft volume maximized 5 min later, when the mesocyclone formed. Simulated reflectivities showed no hook echo and horizontal winds for different height at mid-low levels had a different cyclonic shear at 1430, favorable to mesocyclone formation. Based on the simulated results, the region of positively charged graupel ascended resulting from the region of high liquid water content was lifted by the strong updraft, forming a mid-level strong positive charge region. A lower negative charge region formed by the inductive charging mechanism of collisions between graupel and droplets at the bottom of the cloud, conducive to positive cloud-to-ground flashes. 相似文献
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Yijun Zhagn Wansheng Dong Yang Zhao Guangshu Zhang Hongfa Zhang Chengpin Chen Tong Zhang 《中国科学D辑(英文版)》2004,47(1):108-114
The comprehensive observations on lightning discharges were conducted in Naqu area of Qinghai-Tibet Plateau in summer of 2002. The electric structures of thunderstorms and the characteristics of lightning discharges at initial stage were analyzed by using the observation data. The results show that most of intracloud (IC) lightning flashes were polarities inverted in thunderstorms with tripole electric charge structure and occurred between negative charge region located in the middle of the thunderstorm and positive charge region located at the bottom of the thunderstorm. The radiation characteristics of discharge processes in cloud with longer lasting time involved in Cloud-to-Ground (CG) lightning flashes were similar to that of IC discharges. A lot of radiation pulses were produced in these discharge processes. Because the IC discharges took place at the bottom of thundercloud and were near the ground, they may produce more serious damage to equipment on the ground therefore should not be neglected in lightning protection. 相似文献
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YongBo Tan Chao Chen JieChen Zhou BoWen Zhou DongDong Zhang XiuFeng Guo 《中国科学:地球科学(英文版)》2016,59(7):1440-1453
The upward lightning (UL) initiated from the top of tall buildings (at least above 100 m) is a type of atmospheric discharge. Currently, we understand the nature of the UL from ground observations, but the corresponding theoretical research is lacking. Based on an existing bidirectional leader stochastic model, a stochastic parameterization scheme for the UL has been built and embedded in an existing two-dimensional thundercloud charge/discharge model. The ULs simulated from the experiments with two-dimensional high resolution agree generally with the observation results. By analyzing the charge structure of thunderstorm clouds, we determined the in-cloud environmental characteristics that favor the initiation of conventional cloud-to-ground (CG) flashes and analyzed the differences and similarities of some characteristics of the positive and the negative UL. Simulation results indicate that the positive ULs are typically other-lightning-triggered ULs (OLTUL) and are usually a discharge phenomenon between the ground and the lower positive charge region appearing below the main middle negative charge region. The effect of the previous in-cloud lightning (IC) process of space electrical field provides favorable conditions for the initiation of a positive UL. Its entire discharge process is limited, and the branches of the leader are fewer in number as its discharge is not sufficient. A negative UL is generally a discharge phenomenon of the dipole charge structure between the ground and the main negative charge region. The lower temperature stratification and the sinking of the hydrometeors typically initiate a negative UL. Negative ULs develop strongly and have more branches. The OLTUL is initiated mainly during the development stage of a thunderstorm, while the self-triggered UL (STUL) is initiated mainly during the dissipation stage of a thunderstorm. 相似文献
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Numerical simulation of the effect of lower positive charge region in thunderstorms on different types of lightning 总被引：2，自引：0，他引：2
Combined with the existing stochastic lightning parameterization scheme, a classic tripole charge structure in thunderstorms is assumed in the paper, and then 2-dimensional fine-resolution lighting discharge simulations are performed to quantitatively investigate the effect of lower positive charge (LPC) on different types of lightning. The results show: (1) The LPC plays a key role in generating negative cloud-to-ground (CG) flashes and inverted intra-cloud (IC) lightning, and with the increase of charge density or distribution range of LPC region, lightning type changes from positive polarity IC lightning to negative CG flashes and then to inverted IC lightning. (2) Relative to distribution range of charge regions, the magnitude of charge density of the LPC region plays a dominant role in lightning type. Only when the maximal charge density value of LPC region is within a certain range, can negative CG flashes occur, and the occurrence probability is relatively fixed. (3) In this range, the charge density and distribution range of LPC region jointly determine the occurrence of negative CG flashes, which has a linear boundary with the trigger condition of IC lightning. (4) The common effect of charge density and distribution range of the LPC region is to change the distribution of positive potential well of bottom part of thunderstorms, and inverted IC lightning occurs when the initial reference potential is close to 0 MV, and negative CG flashes occur when the initial reference potential is far less than 0 MV. 相似文献