# A 3D Numerical Model to Estimate Lightning Types for PyroCb Thundercloud
## 3 Simulation Results and Discussion
### Influence of Aerosol Concentrations on PyroCb Electrification  
PyroCb thunderstorms are a distinctive form of high-altitude storm, marked by the presence of aerosol particles emitted from fires. Wildfires are capable of generating high aerosol concentrations, typically ranging between 10,000 cm\({}^{-3}\) and 20,000 cm\({}^{-3}\), as reported in [41; 47; 48]. There is no significant observational evidence indicating that high aerosol concentrations increase cloud electrification in pyroCb storms. According to the sensitivity analysis presented in previous studies [34; 36; 39], there is a noticeable non-linear relationship between the values of positive and negative charge densities and aerosol concentrations which can significantly affect the cloud charge structure. However, this paper does not aim to determine any qualitative link between aerosol concentrations and electrification. Consequently, this study assumes a positive correlation between charge density and aerosol concentrations to conduct the sensitivity analysis of electrification in pyroCb thunderclouds under the effect of wind shear extension. To assess the influence of aerosol, further simulations are carried out for the tripole structure-based pyroCb thunderstcloud using four different values of aerosol concentration--\(N=1000\), 5000, 10,000, and 20,000 cm\({}^{-3}\)--while considering 100 cm\({}^{-3}\) as the base value. During the initial stage of a pyroCb storm, the thundercloud charge structure is typically formed by strong undiluted updrafts, which can create a small volume of positive charge at the cloud's bottom (low-temperature zone). According to the laboratory study by [PERSON] et al. [49], a highly effective liquid water content in the low-temperature zone results in graupel particles acquiring a positive charge and therefore can enhance the LP charge layer in tripole structure with a large background of aerosols. For \(N=100\) cm\({}^{-3}\), the magnitude of the peak density for different charge layers is considered similar to the value of configuration 2 of pyroCb given in Table 1. Similar to the method in Section 3.2, the same simulations are conducted after increasing the charge of the UP and MN regions by 10%, and the LP region by 20%  
Figure 10: Plots of surface charge density \(\sigma\) (**a**–**c**) for a pyroCb thundercloud under the effect of wind shear. of its initial value for each 1000 cm\({}^{-3}\) increase in aerosol concentration (summarized in Table 4). Figure 11(a1-c1,a2-c2) illustrate the variation in the electric potential \(V\) (at maximum field point) and vertical electric field \(E_{z}\) value for different aerosol concentrations \(N\) in pyroCb under the effect of wind shear extension. For \(d=2\) and 4 km, it is observed in Figure 11(a1,b1) that the potential \(V\) of the lightning initiation point increases and remains positive with high aerosol concentrations. When \(d=8\) km, \(V\) becomes negative with a decline in its absolute value for concentrations ranging from \(N=1000\) to 10,000 cm\({}^{-3}\) (Figure 11(c1)). Moreover, the increase in aerosol concentration increases the vertical electric field in the lower dipole (between MN and LP) region of the thundercloud and is also observed to exceed the threshold field value for lightning breakdown as seen in Figure 11(a2-c2). The levels of aerosols also greatly affect the electrical charges on the ground beneath pyroCb thunderclouds. Figures 12 and 13 depict the development of simulated surface charge density \(\sigma\) under the influence of different aerosol concentration levels. The value of \(\sigma\) consistently stays negative for aerosol concentrations ranging from 1000 to 20,000 cm\({}^{-3}\). Moreover, beyond 1000 cm\({}^{-3}\), there is a sharp increase in \(\sigma\), which in turn boosts the probability of +CG strikes.