The Attachment Process of Negative Connecting Leader to the Lateral Surface of Downward Positive Leader in a Positive Cloud‐To‐Ground Lightning Flash

Using high‐speed video cameras operating with framing rates of 20 and 50 kiloframes per second, we captured an attachment process during a positive cloud‐to‐ground flash, which demonstrates the connection of the negative connecting leader (NCL) to the lateral surface of the downward positive leader (DPL) for the first time. When the NCL was initiated, the tip of the DPL had passed the initiation position of the NCL for about 50 m. A common streamer zone (CSZ) was observed when the three‐dimensional distance between the NCL tip and the lateral surface of DPL was about 30 m. It is remarkable to note that a luminous segment (space stem/leader) with a length of about 7 m was captured within the CSZ during the attachment process. The connection between the NCL tip and the lateral surface of the DPL was caused by the development of the CSZ and its inner space leader. Plain Language Summary In the lightning attachment process, the leader connecting behavior is an interesting topic. In the attachment process of a negative cloud‐to‐ground (CG) lightning flash, the “Tip to the lateral surface” connection type has been widely observed, and researchers have carried out a series of studies and discussions on the characteristics and the physical mechanisms of the leader connecting behavior. However, is there also a “Tip to the lateral surface” connecting behavior in the attachment process of the positive CG lightning flash? In this study, we analyzed the attachment process in a positive CG lightning flash that struck on a super‐high building, and focused on the development characteristics of the negative connecting leader and the downward positive leader, as well as the connecting behavior between them. The results allow one to see the detail of leader connecting behavior needed for improving our understanding of lightning attachment process mechanisms. Key Points A rare positive cloud‐to‐ground lightning flash terminated on a 530‐m‐high structure was observed by multi‐stations simultaneously The attachment process of negative connecting leader to the lateral surface of downward positive leader was presented A space stem/leader‐like luminous segment formed within the common streamer zone was observed