# A 3D Numerical Model to Estimate Lightning Types for PyroCb Thundercloud
## 3 Simulation Results and Discussion
### Influence of Aerosol Concentrations on PyroCb Electrification
For different aerosol concentrations, the simulated absolute value of peak \(\sigma\) and their effect on developing probable lightning types are summarized in Table 5. Increased aerosol concentrations within pyroCb events can amplify the negative value of \(\sigma\), even amidst the horizontal displacement of UP charge by wind shear (see Figures 12 and 13). This justifies the occurrence of excessive LP charges within low-temperature regions of thunderclouds during high aerosol conditions, consequently generating high field strength in lower dipole regions. Under extreme aerosol concentrations, such electrical conditions may induce the development of downward positive leaders toward the Earth's surface. This results in the occurrence of +CG strikes primarily underneath the thundercloud core, as observed from the extracted \((x,y)\) coordinates given in Table 5. In the high aerosol case of \(N\geq 1000\) cm\({}^{-3}\), the wind shear extension of UP charge by 8 km from the thundercloud core reduces the field strength between the UP and MN charge layers (Figure 11(c2)) so that the LP charge region no longer shields the MN charge layer above from the ground and \(-\)CG strikes will occur with probable locations far away from +CG striking zones (summarized in Table 5). \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Charge Structure**} & \multirow{2}{*}{**Charge Regions**} & \multirow{2}{*}{**Peak Charge Density**} & \multicolumn{2}{c}{**Percentage of**} \\  & & **(nC/m\({}^{2}\)) at** & **Incernent Rate of** \\  & & \(N=100\) **cm\({}^{-3}\)** & **Density (per** \\  & & \(N=100\) **cm\({}^{-3}\)** & **1000 cm\({}^{-3}\) Rise of** \\  & & & **Aerosol)** \\ \hline \multirow{3}{*}{tripole} & SC & \(-1.1\) & Constant \\  & UP & 2.2 & 10\% \\ \cline{1-1}  & MN & \(-2.5\) & 10\% \\ \cline{1-1}  & LP & 1.5 & 20\% \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Increment rate of peak charge densities in tripole structure-based pyroCb. Figure 11: Figures illustrating (**a1–c1**) the electric potential \(V\) (MV) at maximum field point, and (**a2–c2**) the longitudinal electric field \(E_{z}\) (kV/m) for pyroCb thundercloud with wind shear extension values of (**a**) \(d=2\), (**b**) \(d=4\) and (**c**) \(d=8\) km. The threshold field value of initiation is shown by red dash-dotted lines. Figure 12: Variations in surface charge density \(\sigma\) in pyroCb for aerosol concentrations: \(N=1000\) cm\({}^{-3}\) (**a1–c1**) and 5000 cm\({}^{-3}\) (**a2–c2**) in the presence of wind shear. In brief, the objective of this research is to use numerical representation to depict the tripole structure of pyroCb thunderclouds and investigate the electrical states of the thunderclouds to approximate the probable lightning types and their striking zone on the ground surface. Through the model and simulation, the study has initially revealed the impact of enlarging the lower positive charge layer with the rise in potential and forming negative longitudinal electric field initiation at the thundercloud's bottom. This enlargement leads to a negative surface charge density underneath the pyroCb thundercloud, which can trigger +CG lightning strikes on the ground surface near the core of the storm. Later, the consequences of the wind shear extension on the electrical conditions in a pyroCb storm are investigated. As seen, the lightning initiation potential shifts to the negative value with the wind shear extension of upper charge regions in pyroCb to reduce the absolute field value and can generate \(-\)CG lightning with a large lower positive charge region. Figure 13: Variations in surface charge density \(\sigma\) in pyroCb for aerosol concentrations: \(N=\) 10,000 cm\({}^{-3}\) (**a1–c1**) and 20,000 cm\({}^{-3}\) (**a2–c2**). Additionally, high concentrations of aerosol produced by wildfires can have a significant impact on pyroCb lightning activities.