doi:  10.3878/j.issn.1006-9895.1805.18128
北京一次强飑线过程的闪电辐射源演变特征及其与对流区域和地面热力条件的关系

Evolution of lightning radiation sources of a strong squall line over Beijing metropolitan region and its relation to convection region and surface thermodynamic condition
摘要点击 827  全文点击 174  投稿时间:2018-02-10  修订日期:2018-05-07
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基金:  国家重点基础研究发展计划,国家自然科学基金
中文关键词:  飑线,闪电辐射源,雷达回波,相当位温,对流云区
英文关键词:  squall line, lightning radiation source, radar reflectivity, equivalent potential temperature, convection cloud region
                          
作者中文名作者英文名单位
孙凌Sun Ling中国科学院大气物理研究所中层大气与全球环境探测重点实验室;中国科学院大学
陈志雄中国科学院大气物理研究所中层大气与全球环境探测重点实验室;中国科学院大学
徐燕中国科学院大气物理研究所中层大气与全球环境探测重点实验室;中国科学院大学
孙竹玲Sun Zhuling中国科学院大气物理研究所中层大气与全球环境探测重点实验室
袁善锋中国科学院大气物理研究所中层大气与全球环境探测重点实验室;中国科学院大学
王东方中国科学院大气物理研究所中层大气与全球环境探测重点实验室;中国科学院大学
田野中国科学院大气物理研究所中层大气与全球环境探测重点实验室;中国科学院大学
徐文静中国科学院大气物理研究所中层大气与全球环境探测重点实验室;中国科学院大学;北京城市气象研究所
郄秀书中国科学院大气物理研究所中层大气与全球环境探测重点实验室;中国科学院大学;南京信息工程大学气象灾害预报预警与评估协同创新中心
引用:孙凌,陈志雄,徐燕,孙竹玲,袁善锋,王东方,田野,徐文静,郄秀书.2018.北京一次强飑线过程的闪电辐射源演变特征及其与对流区域和地面热力条件的关系[J].大气科学
Citation:Sun Ling,Sun Zhuling.2018.Evolution of lightning radiation sources of a strong squall line over Beijing metropolitan region and its relation to convection region and surface thermodynamic condition[J].Chinese Journal of Atmospheric Sciences (in Chinese)
中文摘要:
      利用“雷暴973”2015年夏季协同观测期间获得的北京闪电综合探测网(BLNET)总闪辐射源定位、多普勒天气雷达、地面自动气象站和探空资料,详细分析了2015年8月7日北京一次强飑线过程不同阶段的闪电特征,并探讨了闪电与对流区域和地面热力条件之间的关系。飑线过程整体上以云闪为主,根据雷达回波和闪电频数可以将飑线过程分为发展、增强及减弱三个阶段。发展阶段表现为多个孤立的γ中尺度对流降水单体,随着北京城区降水单体的迅速发展,强回波顶高延伸到 -20 oC温度层高度,闪电辐射源高度也逐步增加,闪电明显增多,但总闪电频数整体低于80次/min。增强阶段单体合并,闪电频数快速增长,0 ℃层以上及以下的强回波(>40 dBZ)体积明显增长,飑线形成后,总闪和地闪均达到峰值,分别约248次/min和18次/min,负地闪占总地闪比例90%,辐射源主要分布在线状对流降水区内,辐射源密度峰值出现在5~9 km 高度层。减弱阶段飑线主体下降到0 oC以下并迅速衰减,辐射源分布明显向后部层云降水区倾斜。95 %的闪电发生在对流线附近10 km范围内,即对流云区和过渡区。在系统发展和增强阶段,对流云区与层云区辐射源的活跃时段基本一致;系统减弱阶段,对流降水云区辐射源数量迅速减少。在系统的不同发展阶段,闪电活跃区域对应于冷池出流同平原暖湿气流在近地面形成的相当位温强梯度带内
Abstract:
      Based on the data from "Storm 973" 2015 summer campaign in Beijing area, including the total lightning location data from Beijing Lightning Network (BLNET), S-band Doppler radar data, ground-based automatic weather station observations and radiosonde data, the evolution of lightning activities of a severe squall line process occurring over Beijing metropolitan region on 7 August 2015 was analyzed, and its relation to the convection region and surface thermodynamic condition was also discussed. According to the radar echo and lightning frequency, the whole squall line process can be divided into three stages: developing, intensifying and weakening, and the intra-cloud (IC) lightning flashes predominated during different stages in general. During the developing stage, several isolatedγmesoscale convective cells rapidly developed. With the echo top height of the storm cell over Beijing metropolitan region extending to -20oC level, lightning activities significantly increased, and the lightning radiation sources gradually spread to the upper altitude, but lightning rate was still less than 80 fl/min for the whole system. During the intensifying stage, the flash rate increased rapidly associated with the merging process of the cells. When the squall line formed, the volume of strong radar echo (>40dBZ) for both above and below 0℃ level increased significantly, and total flash and cloud-to-ground (CG) flash peaked with a rate of 248 fl/min and 18 fl/min, respectively. The negative CG flashes accounted for 90% of the total CG flashes. The lightning radiation sources were mainly detected in the linear convection area, and the density of radiation sources peaked at 5~9 km layer. In the weakening stage, the core of squall line dropped below 0 oC level and quickly decayed, with the radiation sources obviously sloping backward to the stratiform clouds. About 95% of total flashes occurred within 10 km of the convective line, namely the convection and transition region. During intensifying and weakening stages, radiation sources reached active period simultaneously in the convection and stratiform region, while during the weakening stage, radiation sources in the convection region declined abruptly in the number. Lightning flashes mainly occurred over regions with strong surface equivalent potential temperature gradient formed by the outflow of convectively-generated cold pool and the relatively warm moist airmass from the plain.
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