Further Studies of Lightning Initiation, Propagation, and Evolution

雷暴及其伴随的闪电每年在美国造成大量人员伤亡和财产损失。然而，我们仍然不了解导致闪电的第一个火花的物理机制，也不知道是什么让火花成长为一个导电通道，首先通过云层，然后通过空气传播到地面。云内闪光，那些只在云内部和周围移动（但不移动到地面）的闪光，对刚刚发射的飞机和太空火箭是一种危险。该项目旨在更好地了解闪电产生的重要过程，闪电在云和空气中的传播，以及闪电从一个小火花到长达数英里的放电的演变过程，这些过程可以在相隔数英里的多个地点发生。该项目将使用来自一组独特传感器的现有数据。知识价值：该项目将利用2011年夏天在佛罗里达州的NASA肯尼迪航天中心（KSC）周围收集的数据，该数据是在先前的NSF奖励下收集的。这些数据来自六组传感器的组合，每一组传感器都能揭示关于闪光灯的不同信息。KSC运行了三个系统，提供了闪电路径（由短步组成）、闪电总电荷和闪电击地点的数据。两个研究阵列的电场变化传感器提供了闪光灯不同部位的位置和电流大小的数据；这些水流可以在千分之一秒或更短的时间内传播50码到几英里。第六个传感器是一个高速摄像机（以50,000 fps的速度运行），它可以产生有关闪电任何发光特征的详细信息，包括闪光起始和正负电荷运动。使用该数据集已经发表了七篇科学论文，还有七篇正在审查或撰写中。然而，可用的多传感器数据集仍然非常丰富和深入。例如，有一天（2011年8月14日），在KSC 50英里范围内有25,500个云内和1,700个云对地闪光，并且在15个风暴日也有类似的良好数据。因此，有许多尚未研究的数据可以用来了解有关闪电产生、传播和进化的新细节。该项目将得到许多计算机工具的帮助，这些工具是在先前的NSF奖励中开发的；这些工具将从项目的第一天起加强数据分析。该项目还将扩展以前的数据集，包括位于KSC附近的墨尔本国家气象局雷达的存档数据。额外的雷达数据将允许将闪电的发生、传播和发展与天气预报员使用的雷暴反射率参数（和其他雷达参数）进行比较。因此，该研究的主要知识价值在于，它将利用现有数据来推进对闪电机制的理解，并更好地表征整个雷暴生命周期中闪电结构的演变。更广泛的影响：肯尼迪航天中心位于每年闪电数量最多的地区之一；这些闪光危及工作人员、太空飞行器和KSC的特殊设备。美国宇航局的任务是安全发射运载卫星和宇航员的火箭，因此对闪电尤为关注。为了继续减少对公众和NASA的闪电威胁，有必要更好地了解闪电是如何工作的；这个项目旨在促进这种理解。该项目将对培养几名新科学家具有重要意义，其中包括一名博士后研究员、一名助理研究员、两名研究生和两名对科学研究感兴趣的物理学本科生。培训包括针对闪电电磁测量的数据分析技术，以及在许多情况下普遍适用的技术（包括计算机编程、计算建模和口头和书面传播结果）。预期的8名项目人员中有4名是妇女。该项目的结果也将在同行评议的文献中广泛传播。因此，该项目主要的更广泛的影响是，在更好地了解闪电和培训新的、多样化的科学家和工程师的基础上，有可能减少闪电威胁。

Thunderstorms and their accompanying lightning flashes are responsible for a substantial number of casualties and property damage each year in the USA. However, we still do not understand the physical mechanisms that cause the first spark of a lightning flash or that allow the spark to grow into a conducting channel that travels to ground first through the cloud and then through the air. Intracloud flashes, those which move only inside and around a cloud (but not to ground), are a hazard for aircraft and space-bound rockets just after launch. This project aims to gain a better understanding of the important processes in lightning initiation, lightning propagation through cloud and air, and lightning evolution from a small spark to an electrical discharge that is miles long and can strike in multiple locations that are miles apart. The project will use existing data from a unique array of sensors.Intellectual Merit: This project will utilize data collected in summer 2011 around NASA Kennedy Space Center (KSC) in Florida, under a prior NSF award. The data come from a combination of six sensor sets, each of which reveals different information about a flash. Three systems were operated by KSC and provided data on the lightning paths (composed of short steps), the overall lightning charge, and lightning ground strike points. Two research arrays of electric field change sensors provided data on the location and amount of electric current for different parts of the flash; these currents can travel 50 yards to several miles in one-thousandth of a second or less. The sixth sensor was a high-speed video camera (operating at 50,000 fps) which yields detailed information on any luminous features of the lightning, including flash initiation and positive and negative charge motion. Seven scientific articles have already been published using this dataset and seven more are either under review or being written. However, the available multi-sensor dataset remains very rich and deep. For example, on one day (August 14, 2011) there were 25,500 intracloud and 1,700 cloud-to-ground flashes within 50 miles of KSC, and there are similarly good data on 15 storm days. Thus, there is much as-yet-unstudied data that can be used to learn new details about lightning initiation, propagation, and evolution. The project will be aided by many computer tools developed in a prior NSF award; these tools will enhance the data analysis from day one of this project. This project will also extend the previous dataset by including archived data from the Melbourne National Weather Service radar located near KSC. The additional radar data will allow comparisons of lightning initiation, propagation, and development to the thunderstorm reflectivity parameters (and other radar parameters) used by weather forecasters. Thus, the main intellectual merit of the study is that it will use existing data to advance the understanding of lightning mechanisms and better characterize the evolution of lightning structure throughout the thunderstorm lifecycle.Broader Impacts: Kennedy Space Center is located in a region with one of the largest numbers of lightning flashes per year; these flashes endanger the workers, space-bound vehicles, and special equipment at KSC. With its mission to safely launch rockets carrying satellites and astronauts, NASA is especially concerned about lightning. To continue reducing the lightning threat for the general public and for NASA, it is essential to better understand how lightning works; this project aims to advance that understanding. The project will be important for the development and training of several new scientists, including one post-doctoral researcher, one research associate, two graduate students, and two undergraduate physics students interested in scientific research. The training involves data analysis techniques that are specific to electromagnetic measurements of lightning as well as techniques that are generally applicable in many situations (including computer programming, computational modeling, and oral and written dissemination of results). Four of the eight anticipated project personnel are women. The results of this project will also be broadly disseminated in the peer-reviewed literature. Thus, the main broader impacts of this project are the potential reduction in lightning threats based on better understanding of lightning and the training of new and diverse scientists and engineers.