【作者】 崔丹；

【导师】 王振会； 肖辉；

【作者基本信息】 南京信息工程大学 ， 大气遥感科学与技术， 2008， 硕士

【摘要】 闪电的形成和发展是云动力过程和微物理过程相互作用的产物,其中云微物理过程不可忽视。但闪电发生在瞬间,能够在极短的时间内观察到云中微物理变化过程是科学家们急要解决的难题,然而深入研究微物理过程的变化对闪电发生的影响,对深刻理解闪电发生过程及其本质有着重要意义。本文选择2007年5月15日的一次东北吉林地区的闪电发生过程作为研究个例,利用多参数雷达资料、闪电定位网监测资料及自动气象站降水资料分析了中尺度对流系统中闪电发生过程的天气背景、降水过程及红外云图演变特征。在此基础上详细分析了闪电发生前后云中的微物理变化过程,同时进一步分析了对降水物理过程的影响。结果表明:此次大范围的降雨及局部的强对流天气是由于中尺度对流云团从西南向东北移动过程中经过吉林省上空,在云团移动过程中,云团前端产生了小范围的强对流云团。通过分析多参数雷达的各个参量在闪电发生过程中的变化情况,找到了与闪电的发生紧密相关的偏振参量K_DP、Z_DR和φ_DP。分析发现闪电前后,对流云上部的差分传播相移率K_DP、差分反射率因子Z_DR和差相移φ_DP有明显的变化,这反映出云中冰相粒子排列取向随着云中电场分布结构的变化而变化。这种闪电发生时冰相粒子排列取向存在明显变化的信息,是一种较好预示闪电发生的方法。以及结合强度图可以更好的分析闪电前后的宏观变化,同时又利用了吉林省闪电定位监测网提供的地闪发生的时间、位置、强度和极性等数据来校验利用雷达资料预测闪电发生的时间位置的准确性,从而论证多参数雷达监测闪电这种方法的是可行的。而通过分析偏振参量数据在闪电前后对流系统的变化,发现在各自变化最明显的区域内,值的变化是完全符合理论的,但在以一个量为基准观察其他两个量时,是不完全符合理论的,是存在差异的,通过分析这些差异是可以确定闪电区域的。同时通过进一步分析地闪与对流性天气系统中降水的关系,发现雷暴中的强烈的电活动与强降水也有很好的对应关系,而与一般性的降雨对应关系较差。中尺度对流系统中的闪电资料可以用来确定对流过程以及其发展趋势和强度,而且闪电资料可以用来预报对流活动的发生和发展。闪电总数与灾害性天气的强弱没有明显的关系,同时负闪与雷暴天气的强弱之间也没有明显关系,只与降水存在一定的关系,负闪频数高,降水强;负闪频数低,降水弱。通过2007年5月15日这天的地闪频数统计分析可得正闪与总闪频次比例不高,但与剧烈的强天气现象却有明显的关系,高正闪电比例对应了剧烈的天气现象。此外,为了实际用图的需要,进行了双偏振雷达数据的产品软件开发,采用的开发语言是VC++,主要介绍了在开发过程中所用到的PPI图形和RHI图形的插值方法及其他一些关键技术。更多还原

【Abstract】 Forming and developing processes of lightning are the results of the interactions between the dynamic processes and cloud microphysical processes, and cloud microphysical processes should not be overlooked. Because lightning occurred in a flash, it is the urgent problem to observe the cloud microphysical processes in a very short period of time for scientists. However the influence of microphysical processes on lightning is significant for better understanding the essence of formation and development of lightning. In this paper, choose the lightning process in Jilin Province of northeast area on May 15, 2007 as a research case. Use multi-parameter radar data, lightning location network monitoring data and automatic weather station precipitation data to analyze the synoptic background, the precipitation process and evolution of cloud infrared images in lightning happening process of the mesoscale convective systems. On this basis, the cloud microphysical changes before and after lightning in the process are analyzed in detail, while further analysis of the influence to the physical processes of precipitation.The results show that the large-scale rainfall and partial strong convective weather due to the course of the mesoscale convective clouds moving from southwest to northeast over Jilin Province. In the process of clouds moving, the front of the cloud gives birth to a strong small-scale convective cloud. By analysis of the change of the various parameters of the multi-parameter radar in the Lightning occurred, we find the polarization parameters of K_DP,φ_dp and Z_DR which closely relate to the occurrence of the lightning. The specific differential phase shift K_DP, differential reflectivity factor Z_DR and differential phase shiftφ_dp change with the orientation of evolved ice particles in the top of the convective cloud before and after occurring of lightning. This could retrieve the changing distribution and structure of the electric field in the cloud. Using this clear discernable direction information of ice particles at the time of lightning has been the better method to forecast the occurrence of lightning. Meanwhile, combined with the strength map we can better analyze the macroscopical changes before and after the lightning. At the same time, use the data of time, location, strength and polarity of the flash occurrence which are provided by lightning positioning network to check the accuracy of the time, location of the lightning forecasted by radar data, this has proved the possibility in using this multi-parameter meteorology radar technology to forecast and monitor lightning earlier. And by analyzing the changes of the data of polarization parameters before and after the lightning in the convection system, we can find the most obvious changes in their respective regions. The changes are fully in line with the theory, but in a parameter-based observation of the other two, are not entirely consistent with the theory, there are some differences. Through the analysis of these differences, we can determine the lightning region.At the same time, further analysis of the relationship between cloud to ground lightning and precipitation in the convective weather systems, we found some strong electrical activity and heavy rainfall which also have a good corresponding relationship in the thunderstorms, and have a poor correlation with general rainfall. The lightning information in mesoscale convective systems can be used to determine the convection process and its development trends and strength. And lightning information can be used to forecast the occurrence and development of convective activity. The total number of lightning doesn’t have the clear relationship to the strength of disastrous weather, while the relationship between negative lightning and strength of the thunderstorm weather also doesn’t clear. There is only a certain relationship with precipitation. The higher frequency of negative lightning, the stronger precipitation, the reverse is also. Through the analysis of the statistical flash frequency in May 15, 2007, we found the positive lightning with the total flash ratio is not high frequency, but the strong and violent weather phenomenon has obvious. Positive lightning in a high proportion is corresponding with the intense weather phenomena.Furthermore, in order to satisfy the needs of practical figure use, we make software developments for these dual-polarization radar data products. The computer development language is used in Visual C++, introduced interpolation methods for the PPI graphics and RHI graphics and some other key Technology in the development process.更多还原