资源环境科技发展态势分析平台

High-speed video and electric field change data have been used to examine the initiation and propagation of 21 recoil leaders, 7 of which evolved into dart (or dart-stepped) leaders (DLs) initiating return strokes and 14 were attempted leaders (ALs), in a Canton-Tower upward flash. Three DLs and two ALs clearly exhibited bidirectional extension. Each DL was preceded by one or more ALs and initiated near the extremity of the positive end of the preceding AL. The positive end of each bidirectional DL generally appeared to be inactive (stationary) or intermittently propagated along the positive part of the preceding AL channel and extended into the virgin air. A sequence of two floating channel segments was formed ahead of the approaching positive end of one DL, causing its abrupt elongation. Plain Language Summary In this paper, we present high-speed video observations of recoil leaders (RLs) which were not obscured by the cloud. We examined the initial positions, morphology, and dynamics of RLs in a Canton-Tower upward flash. Out of a total of 21 RLs, 7 evolved into dart (or dart-stepped) leaders, attaching to the Tower and producing return strokes, and 14 failed to reach the Tower, that is, were attempted dart (or dart-stepped) leaders. We infer that all the RLs were bidirectional with the negative end steadily extending toward the Tower and the positive end generally being stationary or showing intermittent propagation. Each dart (or dart-stepped) leader initiated near the extremity of the positive end of the preceding bidirectional attempted leader. The positive end of one dart (or dart-stepped) leader extended abruptly via connection of at least one floating channel to the positive channel tip.