中国典型区域雷电活动气候特征及其机制分析

选取不同纬度不同下垫面的四川省、山东省和黑龙江省,利用2005-2010年地闪资料,研究了三个典型区域雷电活动气候特征及其物理机制.在不同时间尺度上,三省地闪变化呈现不同的年际、月际及日际变化特征.地闪极性上,四川省西部高原及黑龙江省正地闪比例较四川省东部盆地和山东省高,这是由于高海拔、高纬度地区雷暴云顶高度及南北方雷暴云电荷结构差异造成的.地面盛行风系与地形对雷电活动影响很大,迎风坡为雷电活动频发区域,且直接热力环流圈迎风坡地闪比例较间接热力环流圈高.雷电活动具有较大的区域性,其对气温及不稳定参量有较好的响应,雷暴过程中黑龙江省北部对流有效位能(CAPE)及对流抑制能量(GIN)远小于四川省东部及山东省中部,中层相对湿度及700 hPa相当位温四川省东部最大,山东省中部次之,黑龙江省北部最小.     

一次雹暴的闪电特征和电荷结构演变研究

综合利用SAFIR3000三维闪电定位系统的全闪定位资料与雷达结合对2005年5月31日发生于北京的一次冰雹过程的闪电活动和电荷结构演变特征进行了综合分析.结果表明:该雷暴的闪电活动有两次活跃期,第一个活跃期产生了降雹,降雹结束后,闪电活动突然减少,之后的活跃期产生了更多的闪电,其中一部分处于云砧区.闪电活动峰值超前降雹5 min左右,闪电活动中的地闪仅占6.16%,但正地闪占总地闪的比例达20%,且降雹前的正地闪比例较降雹后要高·降雹发生后,正地闪很少发生.降雹阶段,参与放电的主要电荷区表现为反极性结构,-40℃左右区域为参与放电的主负电荷区,-15℃左右区域为参与放电的主正电荷区,在正电荷区之下,短暂存在一个较弱的负电荷区.降雹结束后,电荷结构经历了持续的快速调整过程,在第2次闪电活跃期,参与放电的主要区域表现为正常的三极性结构,即上正-中负-下正,受西风气流的影响,此三极性结构出现倾斜.动力和微物理过程的分析表明,闪电活动和电荷结构的特征与雷暴云内的动力、微物理过程紧密相关.文中对反极性电荷结构形成的可能机理进行了讨论,并且认为,具有强烈上升气流的灾害性天气可能更易形成反三极性的电荷结构,并在下部两个电衙区的作用下产生较多的正地闪.     

高分辨中尺度雷电预报模式GRAPES_LM的建立及其初步应用试验

为了探索雷电天气的数值预报新方法,在高分辨GRAPES_Meso中尺度预报模式中添加了各种水成物电荷密度预报方程组,同时从传统基于云模式的三维雷电模式中剥离出起电过程和放电过程参数化方案,作为中尺度模式的一种物理过程参数化方案嵌套进中尺度模式,使得整套中尺度模式包含了大气动力、雷电过程及各种物理过程,建立了大气动力-物理过程和雷电过程一体化的数值预报模式GRAPES_LM,建立的GRAPES_LM模式包含了多种复杂的微物理过程参数化方案,其中,包括中国气象科学研究院开发研制的双参数对流云参数化方案;包含了霰/雹与冰晶/雪晶碰撞回弹的非感应起电、霰/雹与云滴碰撞的感应起电及霰碰撞大云滴造成冰晶繁生的次生冰晶起电3种起电参数化方案以及最新的随机双向放电参数化。并利用美国CCOPE观测试验中的个例观测资料(1981年7月19日),进行了初步应用模拟试验,对模式的雷电数值预报的可行性进行了验证分析。结果表明,高分辨率GRAPES_LM模式对1981年7月19日的雷电过程个例做出了成功的模拟预报,较好地给出了雷暴云的动力、微物理和电过程的时空演变,雷电天气数值预报新方法的可行性得到了初步验证。     

人工观测与闪电定位探测雷暴日资料的对比分析

在对比分析人工观测雷暴日资料与闪电定位探测雷暴日资料的基础上,揭示了造成2种资料不一致的原因,并提出了应用闪电定位探测雷暴日资料时应注意的问题。研究结果认为,随着器测资料的积累。可提供1个客观的雷暴日分布场,从而改变人们对雷电分布的固有看法,以消除人工观测资料受多种因素影响而不够客观的局限。     

雷电落点概率和强度预报方法初探

雷电灾害被联合国有关部门列为最严重的十种自然灾害之一,中国国家电工委员会称其为“电子时代的一大公害”。江西是雷电灾害较严重的省份,全省年平均雷暴日为82．9d,每年因雷电灾害造成的直接经济损失达5000～8000万元,伤亡近百人。为减轻雷电灾害损失,迫切需要对雷电落点和强度作出预报。为此,文中根据雷电闪击发生的天气、物理成因,结合国内外有关研究现状,综合应用闪电、雷达、卫星以及中尺度模式、对流参数等资料,采用多参数集成方式,研制分县雷电落点概率和强度预报方法。经试报和实报,雷电有无预报的Ts评分为0．61以上,雷电强度预报均通过了α=0．05的χ^2检验。     

Characteristics of cloud-to-ground lightning in warm-season thunderstorms in the Central Great Plains

In July 2005, a field campaign was conducted in the Central Great Plains to obtain 60-field/s video imagery of lightning in correlation with reports from the U.S. National Lightning Detection Network (NLDN) and broadband electric field waveforms from the Los Alamos Sferic Array (LASA). A total of 342 GPS time-stamped cloud-to-ground (CG) flashes were recorded in 17 different sessions, and 311 (91%) of these were correlated with reports from the NLDN. Only 6 of the 17 recording sessions were dominated by flashes that lowered negative charge to ground, and 11 were dominated by positive CG flashes. A total of 103 flashes recorded on video were correlated with at least one NLDN report of negative CG strokes, 204 video flashes were correlated with one or two positive stroke reports, and 4 had bipolar reports. In this paper, we will give distributions of the estimated peak current, I_p, as reported by the NLDN, of negative and positive first strokes that were recorded on video, the multiplicity of strokes that were recorded on video, and the number of ground contacts per flash that were resolved on video. 41 (40%) of the negative flashes produced just a single-stroke on video, and 62 (60%) showed two or more strokes. The observed multiplicity of negative flashes averaged 2.83, which becomes about 3.14 after correcting for the finite time-resolution of the video camera. 195 (96%) of the positive flashes produced just a single-stroke on video, and 9 (4%) showed two strokes; therefore, the observed multiplicity of positive flashes averaged 1.04. Five out of 9 (56%) of the positive subsequent strokes re-illuminated a previous channel, and 4 out of 9 (44%) created a new ground contact. Simultaneous video, LASA, and NLDN measurements also allowed us to examine the classification of NLDN reports during 3 single-cell storms (one negative and two positive). Based on the LASA waveforms, a total of 204 out of 376 (54%) NLDN reports of CG strokes were determined to be for cloud pulses. The misclassified negative reports had |I_p| values ranging from 3.8 kA to 29.7 kA, but only 58 (24%) of these had |I_p| > 10 kA, and only one misclassified positive report had I_p > 20 kA. Radar analyses showed that most of the negative and positive CG strokes that were recorded on video were produced within or near the convective cores of storms. The radar imagery also showed that single-cell storms tended to produce one polarity of CG flashes at a time, and that such storms could switch rapidly from negative to positive CG flashes when the reflectivity was near maximum. Multiple-cell storms produced both negative and positive flashes over a broad region, but each polarity tended to cluster near regions of high-reflectivity.     

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.     

基于IEC 62305-2的雷电灾害风险管理系统设计

介绍了一种基于国际标准IEC62305-2雷击灾害风险评估方法的雷击灾害风险管理系统的功能和结构。系统基于基础数据库,实现雷电灾害信息的检索与查询、数据统计以及输出,可为防灾减灾提供依据。整个系统主要由评价分析模块、基础数据库模块、决策支持模块和输出模块等组成。风险评估分析模块具有雷灾风险识别、风险评价、风险等级划分功能。决策支持模块能够快速、准确提供雷电灾害的评价结果,提出灾害防护措施,计算灾害补偿的范围和数额,以及对防灾工程和拟建防灾工程进行评价。     

确定雷电定位系统场地误差的参数化方法

本文提出一种根据多站雷电定位资料确定闪电定位系统(LLS)场地误差的方法。该方法假定场地误差具有有限阶三角级数的形式,由雷电方位的多站实测资料,经Orville的本征值技术处理,将问题化为一个非线性无约束极值问题,从而可由对目标函数求极值点来确定场地误差。文中利用1988年夏天在北京地区由三个雷电方位探测器(DF)记录到的4900个实际雷电资料求得了各DF站的场地误差曲线。95％以上的闪电经误差订正后的方位与实测方位的残余偏差在±1°以内,与雷达回波的一致性也有了明显改进。     

基于WRF模式对华北一次飑线过程中雷电活动的间接和直接模拟研究

将非感应起电机制和放电参数化方案耦合到WRF模式的Morrison双参数微物理方案中,并在模式中引入了闪电潜势指数LPI,在此基础上模拟了2009年6月16日华北一次飑线过程,讨论模式对闪电活动再现能力。模拟结果显示,模式能够较好地再现雷达回波和降水分布特征,说明模式对此次飑线过程的宏观和微观特征具有一定的模拟能力。利用计算闪电潜势指数LPI的间接模拟,能够指示出大致的闪电分布特征,但闪电潜势指数LPI分布范围明显大于实际闪电落区;而通过耦合电过程的WRF模式直接输出闪电密度的直接模拟,模拟结果与实际闪电密度分布的对应关系较好,但由于模式中输出的闪电密度为总闪电密度,与观测地闪密度资料相比,模拟的闪电密度偏大。