Automated analysis and statistics of lightning leader speed, local flash rates and electric charge structure in thunderstorms

We introduce new methods for the analysis of complex three-dimensional lightning data produced by Lightning Mapping Arrays and illustrate them by cases of a mid-latitude severe weather producing thunderstorm and a tropical thunderstorm in Colombia. The method is based on the characteristics of bidrectional leader development as observed in LMA data (van der Velde and Montanyà, 2013), where mapped positive leaders were found to propagate at characteristic speeds around 2 · 10^4 m s-1, while negative leaders typically propagate at speeds around 10^5 m s-1. We fit slopes (t-x, t-y, t-z) to approximate leader speed, which can be used to determine the polarity, and summarize flash rate and polarity characteristics in a 3D grid over time. The summarized data can be used to follow charge structure evolution over time, as well as climatological studies comparing lightning parameters with the meteorological environment of storms