【作者】 石玉恒；

【导师】 张义军；

【作者基本信息】 中国气象科学研究院 ， 大气物理学与大气环境， 2011， 硕士

【摘要】 闪电活动的发生、发展和演变与雷暴的微物理以及动力条件有着密切的关系,然而它们关系到目前为止还不十分明确,因此进一步深入开展这方面的研究是十分必要的,这对闪电活动预警预报技术的发展具有重要意义。本研究基于多普勒雷达和闪电探测资料,利用北京以及上海地区多个雷暴个例,分析讨论了雷暴的雷达回波特征参数与闪电活动的相关关系,给出了参数化方案。并在此基础上结合先前研究,提出了对闪电活动结束的预警方案。通过这些分析,本文得到了以下主要结论:1、闪电活动与雷暴的雷达回波特征参数的相关关系北京与上海地区的雷暴雷达回波特征参数与闪电活动都具有较好的相关性。其中北京地区的雷暴,相比超过40dBZ和50dBZ的回波体积,超过30dBZ的回波体积与总闪频次的相关性更好,其中相关系数最高的为-15℃层以上的超过30dBZ回波体积。两个地区的地闪活动也表现出与北京地区全闪活动较为相似的性质。对北京地区雷暴的全闪频次以及地闪频次与各回波体积参数做线性拟合和指数拟合,从拟合结果来看,所有回归方程指数拟合的效果要优于线性拟合。从两个地区的拟合结果可以看出,这两个地区的雷暴在相同层结高度以上的起电过程有一定程度的相似。通过双多普勒雷达反演风场,反演了上海地区4个雷暴个例,对这些个例进行统计发现,雷暴的动力参数与地闪活动有着较好的相关关系。从选取的动力参数来看,较强回波区的上升气流体积与地闪频次的相关性比超过5m/s的上升气流体积以及超过10m/s的上升气流体积高。对雷暴雷达回波参数进行验证,-15℃层以上超过30dBZ的回波体积与0℃层以上的超过30dBZ区域的上升气流体积、超过5m/s的上升气流体积以及超过10m/s的上升气流体积的相关性达到了0.93、0.90和0.86,显示了很高的相关性,从而说明了雷达回波特征参数能较好的表征雷暴的动力条件。2、闪电活动与雷暴动力场的时空关系从上海地区8月25日个例分析来看,将地闪按频次分为三个阶段,在初始发展阶段和成熟阶段,其位置与强回波中心有较好的对应,而在地闪衰减期,其发生位置并不在强回波中心,而是发生在较强回波中心;三个时期的地闪位置都发生在水平风场风速辐合,且风速较小区域,这可能是由于携带电荷的冰相粒子在起电后被风场带入这一地区并“堆积”所致;三个时期的地闪位置都分布在上升气流较强区,并非分布在最强上升区域;三个时期的地闪都分布在雷暴的水平散度的负值区域;在雷暴的发展成熟期,地闪并不分布在强涡度的中心。地闪活动与雷暴的回波以及动力特征有着较好的相关性,在地闪发展初期,雷暴中无强回波（超过50dBZ）体积与强上升气流（超过10m/s）体积以及低层的低散度(小于-10^-2s^-1)体积;在地闪发展活跃期,各参数的体积同地闪频次都具有较高的水平,表现出较好的一致性,这一时期,雷暴的强涡度(大于10^-2s^-1)体积最大值与地闪频次最大有着较好的对应;在地闪衰减期,各参数变化较为一致,雷暴中无强回波和强涡度体积,且强上升气流体积,尤其是0℃层以上的强上升气流体积明显减小,而这一时期开始的高层低散度体积有所增大,这也预示雷暴也开始减弱。3、对闪电活动结束的临近预警方案通过分析北京地区雷暴发现,不但可以使用40dBZ的回波顶高、-15℃层以上超过30dBZ的回波体积及其所占雷暴总体积的百分比可以作为预警参数,还可以使用VPF结合闪电频次来对闪电活动的结束进行预警。并且这两种方案都能取得较好的预警效果。更多还原

【Abstract】 The current research results suggest that there is a close relationship, which is not yet clarified in detail, between lightning activity and thunderstorm’s micro-physics and dynamic conditions. Therefore, it is necessary to carry out further research on this relationship. And it is of vital significance for studying of lightning activity and improving the lightning warning and forecast system.The parameterization scheme between lightning activity with thunderstorm’s micro physics and dynamic conditions is given, according to the data of radar, lightning detection and air sounding for 23 thunderstorms in Beijing and Shanghai area. Based on this and combined with previous studies, a warning method of the end of lightning activity is also gained. The main conclusions are as follows:1. The lightning activity has a strong correlation with the micro-physics and dynamic conditions of thunderstorm in both areas. In Beijing area, the echo volume above -15℃level with reflectivity exceed 30dBZ (V30t-15) has the highest correlation coefficients with total lightning frequency in all temperature levels with reflectivity exceed 30dBZ, which is better than that with 40dBZ and 50dBZ. The feature between echo volume and CG lightning frequency in the two sites is similar to the relationship of echo volume and CG lightning frequency in Beijing site.The result of power fit of the echo volume as a function of total lightning frequency and CG lightning frequency is better than linear fit. Compared the results of data fitting , it shows that the thunderstorm’s Radar Echo Characteristics are similar in both sites.The statistic on 4 cases in Shanghai shows that the CG lightning activity has a good correlation with dynamic condition, in which the volume of updraft in strong echo area is the strongest. The correlation coefficients between V30t-15 and updraft volume, which include updraft volume in 30dBZ area above 0℃layer and above 0℃layer with speed exceed 5m/s and 10m/s updraft volume, are 0.93, 0.90 and 0.86. The result proves that the dynamic condition could be characterized by echo volume.2. Analyzing the case of Shanghai, it is found the following results. The CG lightning activity is divided into three periods, including initial period (P1), active period (P2) and decline period (P3). The CG lightning locates in the strongest echo area in P1 and P2, while in stronger echo place in P3. In three periods, the position of CG lightning locates in wind convergence region, in where the wind has lower speed. The CG lightning position does not locate in strongest updraft area but in stronger area.There is strong relationship between CG lightning activity and the features of echo and dynamic structure. There is no exceeding 50dBZ echo volume and faster than 10m/s updraft volume and no volume of lower than -10-2s-1 divergence in P1. In P2, the CG lightning frequency has a good consistency with all kinds of the volumes. In P3, there is no exceeding 50dBZ echo volume and no volume of more than 10-2s-1 vorticity existing, and the volume of updraft above 0℃layer has a dramatic decline.3. Through analyzing thunderstorms in Beijing site, two warning methods of the end of lightning activity are obtained. There are several parameters could be used as warning factor, which include 40dBZ echo top and V30t-15 with its percent of total thunderstorm volume and echo volume per flash.更多还原