Observation of Electrical Alignment Signatures in an Isolated Thunderstorm by Dual-Polarized Phased Array Weather Radar and the Relationship With Intracloud Lightning Flash Rate

The electrical alignment signatures of ice crystals in the middle and upper parts of a thunderstorm have a physical connection with the strong electric fields within the cloud. By taking advantage of the high spatio-temporal resolution of an X-band dual-polarized multiparameter phased array radar, this paper employs negative K_DP signatures to investigate the variation of electric fields in an isolated thunderstorm within its evolution, and the relationship between the negative K_DP signatures and intracloud (IC) lightning activity. The results show that the radar-inferred strong electric fields distributed in a region of about 8.5–10 km during the developing stage, then extended from about 10 km to the cloud top during the mature stage, with an increasing IC lightning flash rate before the end of the mature stage. Subsequently, the electric fields weakened associated with a large amount of IC lightning discharges. The qualitative analysis results indicate that the evolution of the radar-inferred electric fields associated with the upper charge regions is consistent with the electrification process in the isolated thunderstorm, inferred by the IC lighting activity. In addition, there is a tendency for the increased IC lightning rate as the decrease in average composite K_DP in the middle and upper layers of the thunderstorm, with a time lag of about 5.5 min between the minimum average composite K_DP and the peak IC lightning rate, while a good correlation between the negative K_DP volume and the IC lightning flash rate at a lag of approximately 9 min.