Visualization of lightning location data is a necessary step in analyzing and researching lightning activity patterns. This article uses C# and the cross-platform .NET framework to develop a lightning location data analysis class library and the data-driven client to help lightning researchers improve work efficiency and avoid repeated wheel invention. Lightning Location System Data Analyzer (LLSDA) is a suite of software tools that includes a .NET class library for software developers and a desktop application for end users. LLSDA supports a wide range of lightning location data formats, such as the University of Washington (University of Washington) Global Lightning Location System (WWLLN) and Beijing Huayun Dongfang ADTD Lightning Location System data format, and maintains scalability, allowing the addition of other lightning location data Format. The class library can easily read, parse, and analyze lightning location data, and combined with third-party frameworks can realize grid analysis. The desktop application can be combined with MeteoInfo (a geographic information system open-source project) for secondary development. It has a good GUI and is an open-source tool suite for viewing and visualizing lightning location system datasets.

A rocket-triggered lightning flash containing negative–positive–negative current polarity reversal during its initial stage is analyzed using multiple synchronized observation data. The flash was triggered under a thunderstorm transition zone between the convective region and the stratiform region. Both positive leaders developing in the transition zone and negative leaders developing toward the convective region could be identified. As the negative initial continuous current (ICC) declined, a negative leader was transformed from a recoil leader which turned to break down virgin air off the preconditioned positive leader branch. As the negative leader developing forward, a reactivated breakdown leader bridging the grounding trunk channel and the initiation region of the negative leader caused the current polarity reversed from negative to positive 0.22 ms later, which is reported for the first time. The negative leader channel terminated after propagating for 71.08 ms, and the ICC reversed to be negative again owing to the propagation of another positive branch. The horizontal dipole charge structure contributed to the branching of positive leader and the initiation of negative leader, which combined to produce the upward bipolar lightning. During the positive ICC stage, both positive and negative channels simultaneously contributed to the channel-base current and several negative recoil leaders injecting negative charge to the grounding trunk channel produced a fast decrease of the current.