Attachment Process of A Downward Negative Flash with Multiple Return Strokes Struck to a 356-m-Tall Tower in Southern China

A downward negative flash with nine return strokes struck to the 356-m Shenzhen Tower was analyzed. The high-speed camera captured upward connecting leader (UCL) channels in the first and two subsequent strokes of F1612. The observation results show that none of the downward negative leader channels completely propagated to the tower tip before the occurrence of return stroke (RS), so that the UCL was supposed to be initiated from the tower tip and the attachment process occurred in each RS of this flash. The possible altitude range of the attachment point in each subsequent RS was different. It was found that the larger value of downward dart leader speed might cause the higher altitude of the attachment point. These results could help researchers gain a better understanding of the lightning attachment process, especially occurred in the subsequent return stroke.