【作者】 易笑园；

【导师】 李泽椿； 姚学祥； 张义军；

【作者基本信息】 南京信息工程大学 ， 气象学， 2013， 博士

【摘要】 中国的强对流天气主要有两类：一类以对流性暴雨为主,影响范围大；另一类以冰雹、雷暴大风为主,变化剧烈,影响范围小。对应前者的重要强对流系统之一是α-中尺度对流系统(MαCS,α-Mesoscale Convective System),生命史可超过6小时；对应后者较多的是多单体雷暴或超级单体雷暴,为p或γ中尺度对流系统(Mβ CS或MγCS),生命史大多只有0.5-4小时。这两类强对流系统在发生发展的环境条件上有显著的差异(即MαCS需要有充足的水汽供应,而雷暴系统则需要较强的对流有效位能和垂直风切变)；在空间、热力动力结构及组织演变机制方面有不同的特点。另外,在组成强对流系统的最小单元—对流单体中,存在着动力场、微观场和电活动。本文大量利用观测资料,运用统计分析和个例诊断相结合的方法,对渤海西岸地区特殊的地理环境下,准圆形M a CS和多单体雷暴的多尺度结构演变及其形成机制开展了系统研究,特别是对这两类强对流系统内部闪电活动特征、电荷结构与系统结构的定量化关系进行了探索。主要研究内容和结论如下：1、来自黄海、渤海的偏东风气流对天津地区大雨以上天气过程影响显著。黄海、渤海的存在促使准圆形M α CS造成的对流性暴雨中心的范围扩大、强度增强。对流系统或单体的触发与倾斜的海风锋锋面上(向海洋一侧倾斜)的中尺度垂直环流有关；海风辐合线携带的水汽、辐合抬升等因素与其他对流系统合并,会促使原来的对流系统强烈地发展。2、准圆形MαCS的高层(中心在200hPa)是正涡度、辐散、冷性、反气旋中尺度扰动环流；其下部(400hPa-900hPa)主要为负涡度、辐合、暖心。在发展至成熟期,其云顶具有准圆形、边界光滑、结构紧实的特征与200hPa上存在的中尺度反气旋扰动流场有关,而此时700hPa的中尺度气旋扰动环流不明显,甚至没有。成熟期至消散期的MαCS,其准圆形云顶范围扩大、出现絮状云、边界模糊等特征,这与200hPa上中尺度扰动流场呈放射状出流有关；而此时在700hPa出现了中尺度气旋扰动环流。多单体雹暴合并时的类型不同其物理原因也不同。3、在多单体雹暴中,总闪频数与Set11的相关系数达到0.79。在强降水单体内地闪频数、云闪频数与upV40-6的相关系数在0.63-0.97。在旺盛阶段,固安强降水单体的H(即正电荷高度)不同于其他单体,H较低且正地闪的比例最大。4、无论是MβCS间的合并,还是嵌于MβCS内的M γ CS间的合并,还是对流单体间的合并,均可以通过雷达参量(upV40-6、upFV40-6、downFV40-6)表征,合并后,整个系统的强度和范围增强,而合并瞬间(6-12min)上升气流的强度受到消弱。合并瞬间,H有所下降,但闪电频数只是略有变化。更多还原

【Abstract】 There are mainly two types of severe convective weather in China:one is mainly with the convective torrential rain, which the influence scope is broad, and the other is mainly with hail and thunderstorm wind, changing dramatically and influencing small scope. The α-Mesoscale Convective System (MαCS), one of the systems corresponding to the former, lasts for more than six hours long. The multi-cell thunderstorm or supercell thunderstorm (i.e. α or γ Mesoscale convective system, MβCS or MγCS), most of the systems corresponding to the later, continues only for0.5-4hours long. The environmental condition of two kinds of severe convective weather is different significantly. MaCS needs adequate water supply, while the thunderstorm system requires severe convection effective potential and shear of vertical wind. Moreover, the two types can be distinguished from the view of space, thermal and dynamic structure and organization evolution mechanism. In addition, the severe convective system is composed of convection cell, in which existing the dynamic field, the microscopic field and the electric field having interaction between each other, respectively. In this paper, basing on observation data, using statistical analysis and diagnostic analysis of the case, in the particular geographical environment along the Bohai Sea, the multi-scale structure and formation mechanism of quasi-circle MaCS and multi-cell thunderstorms are researched, especially lightning activity characteristic, charge structure and its relationship with structure change of the severe convective system are analyzed. The content and conclusions of the study are as follows:1. Easterly airflow from the Yellow Sea and the Bohai Sea isa close relationship between the easterly winds and the heavy rain occurred in Tianjin. It is proved that the presence of the Yellow Sea and the Bohai Sea promotes the larger center range and the strengthener magnitude of the convective rainstorm, causing by the quasi-circle M a CS. It can be classified into two types including the triggering type and the touching type, and the landing sea breeze matches with unstable region triggering or strengthening the thunderstorm system. The original convection system will be strongly developed causing by merging with other convective system as a result of vapor, convergence uplift and so on.2. There are positive vorticity, divergence, cold, anti-cyclone mesoscale disturbance circulation in the MaCS high level (center in200hPa), while negative vorticity, convergence, warm heart below400hPa-900hPa. The cloud top of the mature MaCS is characterized by quasi-circle, clear and smooth boundary and compact structure relating to the mesoscale anticyclone disturbance flow field existing at200hPa. However, there is not clear and complete mesoscale cyclone disturbance flow field at700hPa. The physical reasons are diverse for different merge types.3. The correlation coefficient between total flash frequency (ground lightning and cloud flash) with Set11is0.79in multi-cell hailstorm. The correlation coefficient of ground flash frequency, cloud flash frequency and upV40-6is between0.63-0.97. In the exuberant phase, H of GUAN convection cell is different with others, the H is lower and positive CG has larger proportion.4. Regardless of the merger between MβCS, or the merger between MγCS within MβCS, or the merger between convective cells during multi-cell thunderstorm evolution, all of them can be described by the radar parameters (upV40-6, upFV40-6, down FV40-6). The strength and scope of the whole system enhancements after the merger, and the strength of updraft weaken at the moment (6-12min) with the system collapsing. Along with the merger, the height (H) of main positive charge region declines while lightning frequency changes slightly.更多还原