Velocities of Positive Leaders in Intracloud and Negative Cloud‐to‐Ground Lightning Flashes

Abstract

AbstractWe have performed a statistical study on velocities of positive leaders in 553 intracloud (IC) and 220 negative cloud‐to‐ground (−CG) flashes. It is found that velocities of positive leaders in IC and −CG flashes have very similar distributions, with the vast majority in the range of 1 to 3 × 104 m/s. Average velocities are 1.64 and 1.55 × 104 m/s, respectively, for positive leaders in IC and −CG flashes. Velocities of positive leaders in IC flashes show a clear negative correlation with initiation altitudes and leader propagation altitudes, similar to negative leaders in IC flashes. The negative correlation also exists for positive leaders in −CG flashes but is relatively weak. We also found that positive leaders in both IC and −CG flashes propagate with a stable velocity, contrary to downward positive leaders in +CG flashes and upward positive leaders in negative upward and triggered flashes, which were usually found to accelerate during propagations. These results suggest that positive leaders in IC and −CG flashes and those in +CG, upward and triggered flashes propagate with essentially different velocities. The differences and possible reasons are discussed.