罗琪,郑永光,陈敏. 2019. 2017年北京北部一次罕见强弓状飑线过程演变和机理[J]. 气象学报, 77(3):371-386, doi:10.11676/qxxb2019.026
2017年北京北部一次罕见强弓状飑线过程演变和机理
Evolution and development mechanisms of a rare strong arc-shaped squall line that occurred in northern Beijing in 2017
投稿时间:2018-07-20  修订日期:2018-10-23
DOI:10.11676/qxxb2019.026
中文关键词:  弓形回波  飑线  超级单体  演变  机理
英文关键词:Bow echo  Squall line  Supercell  Evolution  Mechanism
基金项目:国家重点研发计划(2018YFC1507504、2018YFC1506804)、国家自然科学基金项目(41375051)。
作者单位E-mail
罗琪 中国气象科学研究院, 北京, 100081
国家气象中心, 北京, 100081
北京城市气象研究院, 北京, 100089 
 
郑永光 中国气象科学研究院, 北京, 100081
国家气象中心, 北京, 100081 
zhengyg@cma.gov.cn 
陈敏 北京城市气象研究院, 北京, 100089  
摘要点击次数: 249
全文下载次数: 362
中文摘要:
      2017年7月7日下午至午夜,河北西北部和北京中北部发生了一次罕见的最大瞬时风力将近12级并伴有大冰雹的强弓状飑线过程,其触发、演变和维持机制等具有较高研究价值。综合多种观测资料和NCEP分析资料,利用“配料法”分析了该次飑线过程的环境条件、触发、演变、风暴结构和弓形回波的形成与维持机制。飑线发生在500 hPa冷涡西南部的前倾槽和低空急流形势下;超过2000 J/kg的对流有效位能(CAPE)、强0—6 km和0—3 km风垂直切变为弓状飑线及其相关超级单体的生成和维持、大冰雹和地面强风的形成提供了有利条件;较低的湿球温度0℃层(~3.8 km)是有利于大冰雹形成的融化层高度;对流层中层高达30℃温度露点差与大的垂直减温率造成环境大气具有强的下沉对流有效位能(DCAPE),利于弓形回波和地面大风的形成。初始对流形成于西北风和西南偏西风之间的地面辐合线附近。地面大风和冰雹主要分布于低黑体亮温(TBB)和以正闪为主的闪电活跃处。雷达回波显示飑线先由线状对流系统发展成为团状超级单体对流系统,最后演变成弓状飑线。超级单体阶段和飑线阶段都有明显的回波悬垂、弱回波区、中气旋(飑线成熟后期为中涡旋)、强后侧入流及其伴随的入流缺口等;对流层中层急流和大的温度露点差是形成强下沉气流并发展出弓状特征的主要原因;大的对流有效位能和下沉对流有效位能以及强风垂直切变是飑线维持的原因。
英文摘要:
      Based on the NCEP (National Centers of Environmental Prediction) analysis data and various observations from automatic weather stations (AWS), cloud-to-ground lightning positioning system, stationary meteorological satellites and weather radars, the present study uses a "ingredient-based method" to comprehensively analyze environmental conditions, evolution characteristics, trigger and development mechanisms of a rare strong arc-shaped squall line with maximum instantaneous wind on nearly F12 scale and large hails. The squall line originated on the southwestern side of a 500 hPa cold vortex and swept northwestern Hebei Province and central and northern Beijing during the period from afternoon to midnight on 7 July 2017. The strong low-level jet, large convective available potential energy (CAPE) above 2000 J/kg and intense 0-6 km and 0-3 km vertical wind shears were very favorable for the development and maintenance of the squall line. A supercell storm embedded in the squall line produced large hails and high winds. The lower level of 3.8 km altitude for the wet bulb temperature 0℃ was in favor of producing large hails. Dew-point deficit that was up to 30℃ in the middle troposphere and large vertical temperature lapse rate caused large downdraft convective available potential energy (DCAPE), which promoted the formation of bow echoes and high winds. The convection initiation of the squall line was triggered near a surface convergence line between northwesterly winds and southwesterly winds. High winds and large hails were mainly located in the low TBB and active positive cloud-ground lightning area. Radar observations show that the squall line developed from a linear convection system to a cluster supercell storm, and finally to an arc-shaped squall line with significant overhang echoes, weak echo regions, mesocyclone (or mesovortex) and strong rear inflows which caused rear inflow notches. Intense downdraft induced by the strong jet in the middle of the troposphere and high dew-point deficit was the main cause for the formation of the bow echoes in the squall line. The mechanisms of maintaining the squall line and bow echoes include large CAPE and DCAPE and strong vertical wind shear.
HTML   查看全文   查看/发表评论  下载PDF阅读器
分享按钮