吴芳芳,俞小鼎,王慧,商建,周文君. 2019. 一次黄海之滨中尺度对流复合体多尺度结构特征观测研究[J]. 气象学报, 77(5):785-805, doi:10.11676/qxxb2019.057
一次黄海之滨中尺度对流复合体多尺度结构特征观测研究
An observational study of multi-scale structural features of MCC on the coast of the Yellow Sea
投稿时间:2018-08-22  修订日期:2019-03-12
DOI:10.11676/qxxb2019.057
中文关键词:  中尺度对流复合体  飑线  中尺度涡旋  龙卷  多尺度结构特征
英文关键词:MCC  Squall line  Mesovortices  Tornado  Multi-scale structural features
基金项目:国家自然科学基金(41775044)、中国气象局预报员专项(CMAYBY2017-028)、江苏省北极阁基金(BJG201902)。
作者单位E-mail
吴芳芳 江苏省盐城市气象局, 盐城, 224005  
俞小鼎 中国气象局气象干部培训学院, 北京, 100081 xdyu1962@126.com 
王慧 上海中心气象台, 上海, 200030  
商建 江苏省盐城市气象局, 盐城, 224005  
周文君 江苏省盐城市气象局, 盐城, 224005  
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中文摘要:
      2006年7月3日傍晚到4日凌晨,苏北到黄海的一个中尺度对流复合体(MCC)产生了系列龙卷、直线型对流大风和强降水,利用常规高空地面观测、区域自动气象站、卫星云图以及多普勒天气雷达资料,详细分析此次中尺度对流复合体的结构和产生的天气背景。主要结论如下:(1)该中尺度对流复合体高层为对应分离背景场的强辐散,中层在副热带高压西北侧和500 hPa东移的短波槽前,地面位于锋面气旋暖区内;该中尺度对流复合体发生在中等到强的对流有效位能、强的深层(0—6 km)和低层(0—1 km)风垂直切变环境下;(2)该中尺度对流复合体主要垂直环流特征为:近地层东南气流和其上的中低层西南暖湿气流从对流复合体南部流入到复合体中心,复合体后部对流层中低层和中层为较干冷的西北气流夹卷进入中尺度对流复合体,导致降水蒸发冷却形成强烈下沉气流,产生带有西北风动量的下沉气流,到地面形成β中尺度冷池,冷池与周边暖湿气流的交界处为β中尺度阵风锋,同时中尺度对流复合体位于对流层低层到地面部分形成深厚冷池导致的雷暴高压,阵风锋前部有β中尺度暖低压;中尺度对流复合体中高层由于水汽凝结潜热释放加热形成暖心结构,位于对流层中层的主要特征为β中尺度气旋性涡旋对应的中尺度低压,对流层高层存在β中尺度辐散反气旋环流;(3)多普勒天气雷达探测揭示该中尺度对流复合体成熟阶段主要呈现为线性结构,主要构成是一条尺度在150—200 km的活跃弓形飑线,还有数条较弱的呈气旋性弯曲的对流雨带,雨带旋入共同的涡旋中心,该涡旋中心与地面锋面气旋的中心相对应(重合),同时也是相应中尺度对流复合体的β中尺度气旋的中心,直径为40—60 km;(4)在上述活跃弓形飑线的前侧出现多个中尺度涡旋,4个EF2级龙卷和3个EF1级龙卷都发生在这些中尺度涡旋内,导致龙卷的中尺度涡旋水平尺度为4—5 km,旋转速度接近超级单体的强中气旋旋转速度,垂直伸展比超级单体中气旋浅薄,形成机制也与超级单体中气旋有明显差异;(5)该中尺度对流复合体成熟阶段的云系尺度为1000 km,其中低于220 K (-52℃)冷云盖的尺度在400 km左右,其内部结构的主要构成是一条150—200 km长的活跃弓形飑线,地面β中尺度冷池和阵风锋,沿着弓形飑线前侧出现多个尺度为4—5 km的中尺度涡旋,其中部分中尺度涡旋导致尺度只有几十至几百米的EF1和EF2级龙卷,呈现出明显的多尺度结构特征。
英文摘要:
      From the evening of 3 July to early morning of 4 July 2006, a mesoscale convective complex (MCC) from northern Jiangsu to the Yellow Sea spawned a series of tornadoes, linear convective winds and heavy precipitation. In this paper, the synoptic weather background and the MCC structure are analyzed in detail using conventional surface and upper-level observations, regional automatic weather station observations, satellite cloud images and Doppler weather radar data. The main conclusions are as follows. (1) In the upper levels, strong divergence developed in response to the background field. In the middle levels, the MCC was located in front of an eastward-moving short-wave trough to the northwest of the subtropical high at 500 hPa. In the surface, the MCC was located in the warm zone of a frontal cyclone, in the presence of medium-to-strong convective available potential energy (CAPE) and large vertical wind shear in a deep layer (0-6 km) as well as in the low level (0-1 km). (2) The main vertical circulation exhibits some characteristics. The southeasterly flow in lowest layer and the warm, moist southwesterly flow in the middle-lower levels transported air mass from the south of the MCC to the center of the MCC. Northwesterly flow prevailed in the rear of the MCC, was relatively dry entrained into the MCC, causing evaporative cooling and strong descending motion. The downdraft with momentum from northwesterly winds builded a meso-β scale cold pool near surface, and the meso-β scale gust front formed along the boundary between the cold pool and the surrounding warm and moist airmass. Cold high pressure formed from the ground to the lower troposphere (thunderstorm high pressure), while the meso-β scale low pressure developed in front of the gust front. A warm core emerged in the middle and upper levels of the MCC due to the latent heat release caused by condensation. In the middle troposphere, the MCC was characterized by a meso-β scale cyclonic vortex and low pressure; in the upper troposphere, meso-β scale anticyclonic divergent flow prevailed. (3) Doppler weather radar observations revealed that the MCC at mature stage mainly presented a linear structure. The main component of the MCC was an active bow squall line on the scale of 150-200 km, while several weak convective rain belts with a cyclonic curvature existed. Several rain belts merged into the common vortex center, which coincided with the center of the frontal cyclone in the ground and also the center of the meso-β scale cyclone of the corresponding MCC with a diameter of 40-60 km. (4) Multiple mesovortices appeared in front of the active bow squall line, and four EF2 tornadoes and two EF1 tornadoes occurred in these mesovortices. The mesovortices had horizontal scale of 4-5 km, with the rotation speed close to strong mesocyclones in super-cells but less vertical extension, and the formation mechanism was also significantly different from cyclones in supercells. (5) The scale of the cloud system at the mature stage of the MCC was 1000 km in which the coldest part below 220 K (-52℃) was about 400 km. The main internal structure of the MCC included a 150-200 km long active bow squall line, a meso-β scale cold pool and the gust front in the ground, and mesoscale vortexes on the scale of 4-5 km in front of the bow squall line. Some mesoscale vortices led to the formation of EF1 and EF2 tornadoes on scales of only tens to hundreds of meters. The entire system showed obvious multi-scale structural features.
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