A total of 254 flashes observed in 14 mesoscale convective systems in Chongqing, China during the summers of 2014–2015 were used to investigate the characteristics of lightning flashes in stratiform regions (stratiform lightning flashes). The data were analyzed and combined with data from an S‐band Doppler radar system. The results show that the reflectivity characteristics of stratiform lightning flashes are different from those of convective lightning flashes. More than 90% of the stratiform lightning flashes had close spatial relationship with the areas in which bright bands were identified in the vertical direction. The reflectivity at the first detected very high frequency sources of most stratiform lightning flashes decreased with increasing core reflectivity within the lightning extension area. Further investigations showed that only a small proportion (≤10%) of the stratiform lightning flashes were directly initiated by the charge corresponding to the reflectivity cores. It suggests that the relationship between the reflectivity cores (mostly bright bands) and stratiform lightning flashes is close in spatial, but different in causality. Some In situ electrifications in stratiform regions, such as non‐riming non‐inductive electrification and melting electrification, are inferred to cause this relationship. The stratiform lightning flashes initiated from lower altitudes tended to have a lower maximum reflectivity within their lightning areas, but a higher maximum reflectivity in the vertical direction of their initiation locations than flashes initiated at higher altitudes.

Data from an S‐band Doppler radar system and a three‐dimensional very high frequency (VHF) radiation source location system in Chongqing, China were combined to analyze the characteristics of stratiform lightning flashes associated with the charge layer near the 0^oC isotherm (SL0s) In 10 mesoscale convective systems during the summers of 2014–2015. Most of the SL0 events occurred during the dissipating stage of two thunderstorms. The bright band was found to have a very close relationship with the initiation of the SL0 events. The non‐inductive and inductive charging mechanisms associated with the process of melting ice particles were inferred to contribute to the charge of the bright band area. The reflectivity at the first located VHF radiation source (FirstS) of the SL0s was always weaker than that in the reflectivity core within the lightning area. The stronger the reflectivity core, the greater the difference between the reflectivity and the reflectivity core. The SL0s generated by the thunderstorms with low SL0 frequency tended to have weaker reflectivity at the FirstS, but a stronger reflectivity core in the lightning area than that of the thunderstorms with high SL0 frequency. In the storms with low SL0 frequency, SL0s occurred only when the initiation height of the stratiform lightning flashes decreased gradually towards the height range of the SL0s; but in one storm with high SL0 frequency, the SL0s were generated simultaneously with the stratiform lightning flashes initiated at a high level. It gives a clue that the melting charging mechanisms may enhance the charge density of the bright band area.

Using a 10‐year data set of cloud‐to‐ground lightning (CG) flashes, the climatological characteristics of ±CG flashes with a large peak current (>75 kA or <−75 kA) (±LPCCGs) are for the first time obtained in China’s most populous areas in terms of density distribution, seasonal variation, and monthly and diurnal evolution. The results show that the distribution of +LPCCG flashes has evident seasonal variations, while the activity center of −LPCCG flashes always remains in Southwest China. The diurnal evolution of +LPCCG flash percentages in southern China’s Mainland shows an opposite trend to that in the north. Furthermore, the peak current distributions of +LPCCG flashes in most of China’s mainland are found to be distinct from those shown in other regions of the world. Additionally, Southwest China is found to be an important and special area for LPCCG flash activity in China. Not only is it the density center of ±LPCCG flashes, but the peak current distribution of −LPCCG flashes in this region also shows an evidently different pattern from those in other regions. The diurnal evolution of the ‐LPCCG/+LPCCG flash frequencies in Southwest China also shows a different pattern from that in other regions.

To investigate the characteristics of regions exhibiting multiple lightning initiations within a finite volume and a short time, the lightning location data obtained from the convective regions of 14 mesoscale convective systems were analyzed in combination with data from radar. In total, 415 out of 5996 radar grids (1 km × 1 km × 0.5 km) were found to initiate more than one flash within 6 min. Only 49 grids showed an initiation density of more than two flashes within 6 min. The grids with high flash initiation densities were found to have a similar distribution to those with one lightning initiation within 6 min, in terms of altitude and reflectivity relative to altitude. They also showed similar trends in their frequency evolution. The grids with higher initiation densities seemed to be more concentrated in the altitude range of 9–13 km. However, only one was found to form at a lower altitude near the melting level when lightning initiation clearly declined. Moreover, the spatial relationship of this lower higher-initiation density grid to the reflectivity core was different to that in the main altitude range. In this paper, the possible dynamic and electrical mechanisms of the formation of this lower higher-initiation density grid are discussed.

To investigate the characteristics of extension areas (mainly the propagation areas of negative leaders in this study), the lightning location data of 254 lightning flashes initiated in the stratiform regions (stratiform lightning flashes) of 14 mesoscale convective systems (MCSs) are analyzed. The results show that most of the flashes have a relatively small lightning area (LA) (≤100 km²), although they are initiated in the stratiform regions. In small or developing MCSs, most negative leaders of stratiform lightning flashes concentrate within the 9–12‐km altitude range. In other MCSs with a large‐sized and developed stratiform region, besides being in this high‐altitude range, the negative leaders are also found to propagate more frequently in a low‐altitude range of 5–7 km. Further analysis indicates that most of the stratiform lightning flashes with a large LA (>100 km²) propagate their negative leaders within the high‐altitude range, no matter where they are initiated. Moreover, the stratiform lightning flashes with or near the largest LA tend to be initiated 4–6 km below their negative leaders, while most of the stratiform lightning flashes usually propagate their negative leaders horizontally within ±1 km of the first detected very‐high‐frequency (VHF) radiation source. It is inferred that some in‐situ electrifications occurring before and during the formation of the high reflectivity layers in the low‐altitude range contribute to these flashes, although the influence of the advection charges from the convective regions still cannot be totally ruled out.