Electrical Alignment Signatures of Ice Particles Before Intracloud Lightning Activity Detected by Dual‐Polarized Phased Array Weather Radar

Abstract The cloud electrification process has great significance in understanding the microphysical properties, electrical characteristics, and evolution of thunderstorms. This study employs an X‐band dual‐polarized multiparameter phased array weather radar (MP‐PAWR) to observe the electrical alignment signatures of ice particles before the first intracloud (IC) lightning flash, and to explore the evolution of the upper charge region in the early electrification stage of an isolated thunderstorm. Negative K DP signatures associated with vertically oriented ice particles by strong electric fields in the upper parts of the thunderstorm are analyzed by introducing composite K DP , which is defined as a minimum K DP value observed in a vertical column across all elevation scans at each specific horizontal grid point at and above a designated layer. About 7 min before the first IC lightning flash, the mean canting angle of ice particles in the upper parts of the cloud changed from horizontal to vertical by strong electric fields, and the concentration of vertically aligned ice particles on the top of the cloud reached the maximum 30 s before the first IC lightning flash. These signatures exhibit an early electrification process in the upper parts of the thunderstorm. These results indicate that with the high spatial and temporal resolution, MP‐PAWRs have the ability not only to detect the rapid evolution of microphysical structures but also to observe the early electrification of thunderstorms, which will facilitate forecasting IC lightning flash initiation combined with graupel presence signatures in the mixed‐phase region in normal operation.