The lightning very high frequency(VHF) radiation location system based on the short-baseline time-difference of arrival(TDOA) technique provides an effective approach to describe the temporal and spatial development of lightning discharge in two dimensions with high resolution.A negative single-stroke cloud-to-ground(CG) lightning flash was analyzed in detail using the radiation location results and synchronic fast/slow electric field changes.The long-duration preliminary breakdown process appeared to propagate with bi-directional leader channels.The two negative simultaneous discharge channels sloped down with a considerable horizontal component in the lower positive charge region at speeds of about 105 m s-1.The stepped leader was clearly converted from one channel of the preliminary breakdown process and spread downwards with branches.The speeds of the stepped leaders were about 105 m s-1.The K processes after the return stroke could either directly initiate from the start region with negative polarity lightning discharge,or initiate from a new region in the cloud as negative recoil streamers.All K processes propagated along the preceding electrified channel,while not all K processes initiated from the tips of positive breakdowns.The speeds of the K processes were about 106–107 m s-1.
Gigantic jet(GJ) is a type of large-scaled transient discharge which occurs above thunderstorms.It connects the thunderstorms and ionosphere directly.Compared with the other transient luminous events(TLEs),gigantic jet is very difficult to be seen from the ground.We report a GJ event that was clearly recorded in eastern China(storm center located at 35.6°N,119.8°E,near the Huanghai Sea) at 20:16:22(local time) on 12 August,2010.It is by far the furthest from the equator ground-based GJ recorded over summer thunderstorm.The top altitude of this GJ was estimated to be about 89 km.The GJ-producing storm was a multi-cell thunderstorm and the GJ event occurred in the storm developing stage,with the lowest cloud-top brightness temperature about 73°C and the maximum radar echo top around 17 km.Altitudes with reflectivity of 45 dBZ were estimated to reach 12-14 km.Different from results from other countries that positive CGs(Cloud-to-ground lightnings) dominated during a time period centered at GJ,our study shows that negative CGs dominated during a time period centered at the GJ event and during most of the storm lifetime in this study,indicating a diversity of the lightning activity in the GJ-producing storms.It is interesting that two different storms produced two types of TLEs,that is,the GJ-producing storm only produced one GJ event during its lifetime and five sprites were produced over another storm,different from the other study that sprites and GJs were usually produced by the same storm,enriched the knowledge of GJ-producing storms.In addition,the GJ event in this study is located beyond the effective coverage area(30°S-30°N) of the ISUAL instruments onboard the FORMOSAT II satellite,and results of this study could be useful for GJ studies in the future.
