Time series data of lightning flash rates, aerosol optical depth (AOD), surface relative humidity, potential temperature, and convective available potential energy (CAPE) for 14 consecutive summers (2001–2014) over central eastern parts of China (32.5°–40°N, 100°–120°E) have been analyzed to investigate the impact of aerosol on the lightning flash rate. The Pearson correlation and the partial correlation are used to study the linear correlations between the lightning flash rate and AOD, potential temperature, surface relative humidity, and CAPE. The results show that the lightning flash rate is positively correlated (r = .64) with AOD under relatively clean conditions (AOD < 1.0), which may result from aerosol microphysical effect. In the situation of high aerosol concentration (AOD > 1.0), the correlation between AOD and lightning flash rate is not obvious (r = −.06), which may be due to the radiation effect of aerosol and the decrease of the number of large ice particles caused by excessive aerosol concentration. CAPE and surface relative humidity are both positively correlated with the lightning flash rates under relatively clean (AOD < 1.0) and relatively polluted (AOD > 1.0) conditions. Potential temperature is moderate positively correlated with the lightning flash rate under relatively clean conditions (r = .51, AOD < 1.0) but shows no significant linear relationship under relatively polluted conditions (r = .07, AOD > 1.0).

High temperature and pressure during lightning can quickly trigger multiple chemical reactions in the air, resulting in considerable impacts on aerosols, atmospheric chemistry, and air quality. Here, new particle formation (NPF) events motivated by lightning flashes were captured during an observation at Mt. Tai in summer 2017 for the first time. Numerous ultrafine particles were formed during the lightning events, leading to increases in nucleation and Aitken mode aerosols by 18.9 and 5.6 times, respectively. The formation rate (FR) and growth rate (GR) during lightning‐generated NPF were 67.1 cm⁻³·s⁻¹ and 20.1 nm·h⁻¹, which were 61 and 1.7 times higher than the averaged daytime NPF. Moreover, chemical composition of aerosols was strongly influenced by lightning NOx. Nitrate aerosol (NO₂⁻ and NO₃⁻) signals intensified significantly (by 11.9% and 12.4%, respectively) during the lightning‐generated NPF, which contrasted with the sulfate aerosols measured in previous studies (non‐lightning NPF). Meanwhile, lightning contributed noticeably to surface NO₂ concentrations. Accompanying the uplifting airflows before rainfall, surface air pollutants (SO₂, NH₃, and NOx, etc.) can be transported above the top of the planet boundary layer, which plays an important role in NPF. The NPF in the hot lightning channels resulted from pollution NOx and lightning NOx, with the latter dominating. Finally, lightning‐generated pollutants, including NOx and aerosols, were delivered down to the surface with descending airflows.

Numerical simulations are performed to investigate the effect of varying CCN (cloud condensation nuclei) concentration on dynamic, microphysics, electrification, and charge structure in weak, moderate, and severe thunderstorms. The results show that the response of electrification to the increase of CCN concentration is a nonlinear relationship in different types of thunderclouds. The increase in CCN concentration leads to a significant enhancement of updraft in the weak thunderclouds, while the high CCN concentration in moderate and severe thunderclouds leads to a slight reduction in maximum updraft speed. The increase of the convection promotes the lift of more small cloud droplets, which leads to a faster and stronger production of ice crystals. The production of graupel is insensitive to the CCN concentration. The content of graupel increases from low CCN concentration to moderate CCN concentration, and slightly decreases at high CCN concentration, which arises from the profound enhancement of small ice crystals production. When the intensity of thundercloud increases, the reduction of graupel production will arise in advance as the CCN concentration increases. Charge production tends to increase as the aerosol concentration rises from low to high in weak and moderate thundercloud cases. However, the magnitude of charging rates in the severe thundercloud cases keeps roughly stable under the high CCN concentration condition, which can be attributed to the profound reduction of graupel content. The charge structure in the weak thundercloud at low CCN concentrations keeps as a dipole, while the weak thunderclouds in the other cases (the CCN concentration above 100 cm⁻³) change from a dipole charge structure to a tripole charge structure, and finally disappear with a dipole. In cases of moderate and severe intensity thunderclouds, the charge structure depicts a relatively complex structure that includes a multilayer charge region.

The effects of the liquid water content (LWC) and mixing ratio of hydrometeors in the simulation of convective precipitation in Wuhan, Hubei Province, China, are investigated using a three-dimensional convective rainstorm model. The microphysical processes of warm and cold clouds are considered into microphysical parameterization. The warm-cloud process is dominated by the combined effects of condensation and drop coalescence. The cold-cloud process is initiated mainly by production of graupel, and the microphysical parameterizations are used to predict the mixing ratio of cloud droplets, rain, ice crystals, snow, and graupel. The simulations results show that 80% rainfall is derived from warm cloud microphysical processes, and the rest is produced by cold cloud microphysical processes. The mixed phase microphysical process can invigorate the production of convective rainfall and enhance the liquid water content (LWC). In addition, the vertical distribution of LWC is mainly concentrated at the height isotherms of −10 to −20 °C in precipitation and the concentration area of LWC matches the distribution range of graupel particles. However, the growth of graupel particles depend on the microphysical processes of nucleation and propagation between rain and graupel particles (NUrg) and collision and coalescence between cloud droplets and graupel (CLcg), in which NUrg is a major source of graupel particles and the contribution of the process accounts for 77% of the amount of graupel particles.

Previous studies have generally acknowledged that lightning propagation behaviors and lightning types are closely related to the unbalanced charge amount and vertical stratification of charge structure. In this study, the total charge amount remains nearly balanced (±5%) between the adjacent charge regions where discharges initiate to avoid the interference of a total charge imbalance. Significant influences on the leader propagation tendency and lightning type are revealed by investigating different horizontal charge distribution features emphasizing on the effects of the charge distribution uniformity and the relative position of the high‐density charge center. Sensitivity experiments are performed with a two‐dimensional stochastic discharge model and demonstrate the following. Under a symmetric charge distribution, the more uniform charge distribution is conducive for leaders propagate horizontally; the charge being more compact in the central zone is favorable for vertical extension of leaders. Under an asymmetric charge distribution, a horizontal shift of high‐density charge center is conducive to the extension of leaders in the offset direction. Different charge distributions will change the electrical energy of charge regions resulting in various lightning behaviors. Various charge distributions provide favorable conditions for some lightning flashes (including positive cloud‐to‐ground flashes [PCG], “bolt‐from‐the‐blue” [BFB] flashes and gigantic jets). PCGs are favorably triggered with the more compact upper positive charge (P) and more uniform middle negative charge (N), and BFB discharges can be triggered between the P and N regions when the high‐density charge center in the P region is horizontally shifted. A possible method is provided to explain various lightning behaviors.

A self‐sustained charge neutrality parameterization scheme of intracloud (IC) lightning is presented in this paper. The scheme contains the following features: simultaneous development of multiple branches, polarity asymmetry of positive and negative leaders, nonlinear electrical parameters, complete charge neutrality, and channel decay and reactivation. Nonlinear electrical parameters and charge neutrality are the key factors that determinate channel decay and reactivation. To demonstrate the simulation capacity of this scheme, two simulated intracloud flashes by this scheme under the tripole charge structure are chosen for analysis. These two IC flashes show clearly the above features, where reactivation processes that initiated from different branches and the real‐time changes in nonlinear electrical parameters are mainly analyzed. The simulation results are in line with the current knowledge on lightning, which also suggests that the new scheme may become a useful tool to deeply explore the discharge phenomena involving channel decay and reactivation.