Development of the First Stroke Leader in Negative Cloud‐to‐Ground Lightning During Thunderstorm Evolution

Abstract Using continuous broadband sferic observations, we reveal for the first time how the horizontal development and duration of the first stroke leader evolve throughout the life cycles of thunderstorms, based on the spatiotemporal characteristics of initial breakdown pulses and the first return strokes in negative cloud‐to‐ground flashes (NCGs). It was found that the horizontal propagation and duration of leaders are significantly longer in the incipient stage than in the mature stage. During the mature stage, NCGs with stronger peak currents and higher multiplicities tend to exhibit shorter leader durations, leading to a shift in the overall distribution toward shorter timescales. In contrast, weaker and lower multiplicities NCGs tend to produce leaders with greater horizontal extents and longer durations. First stroke leaders with short duration and limited horizontal propagation tend to initiate along the edges of convective cores and in regions of weak radar reflectivity, where the associated first return strokes exhibit stronger peak currents. Conversely, leaders initiated within the convective cores typically exhibit more extensive horizontal propagation and longer durations but are associated with weaker peak currents. Statistical results show that leader duration decreases with increasing peak current following a power‐law relationship and increases linearly with horizontal propagation distance. The potential influence of storm‐stage‐dependent charge structure distributions on the initiation and propagation of the first stroke leader is discussed, suggesting that the development of the low positive charge region plays a regulatory role.