## 7 Influence of Tall Structures on Atmospheric Electrical Activity
It is relatively easy to locate its radiation source, through electrical detection, and optical detection [35; 44; 118]. Figure 12 depicts the electromagnetic signals captured during the initial phase of the artificial lightning experiment. According to the statistical analysis, the peak current of precursors ranges between 10 and 35 A, with an average value of 25.4 A, and the waveform duration averages approximately 2.1 \(\upmu\)s. The peak current of the upward leader (UPL), on the other hand, falls between 18 and 45 A, with an average value of 32.7 A, and its waveform duration averages about 3.7 \(\upmu\)s. Both currents are greater than those of the precursors. These observed results align closely with previous research findings [49; 119]. According to the leader model [53; 54; 55; 56], a heightened environmental electric field facilitates the ability of the upward leader to initiate. Conversely, a space charge with a higher density increases the likelihood of leader development failure. Furthermore, a space charge region with a smaller radius enhances the propensity of the upward leader to initiate. Among these parameters, the environmental electric field is the most significant factor [120]. Figure 11: Guangzhou Tower was struck by lightning from the network (**a**). Before the completion of Guangzhou Tower (**b**), and after the completion (**c**), the lightning distribution within 1 km of Guangzhou Tower, and the red triangle represents the location of Guangzhou Tower [116]. Figure 12: Channel-base current waveform (black line) and close B-field signals (blue line) at the triggered site, during the precursory stage of negative rocket-triggered lightning flashes (self-drawing). [PERSON] et al. [121] used the physical model of the leader to calculate the minimum environmental electric field (\(E_{stab}\)) at different heights and established a functional relationship between \(E_{stab}\) and height through nonlinear fitting:  
\[E_{stab+}(H)=[\frac{306.7}{1+H/6.1}+\frac{21.6}{1+H/132.7}]\delta \tag{8}\]  
\[E_{stab-}(H)=[\frac{723}{1+H/10}+4]\delta \tag{9}\]  
\[\delta=(P/P_{0})(T_{0}/T) \tag{10}\]  
In the above formulas, \(P_{0}\) and \(T_{0}\) represent the standard atmospheric pressure and the standard atmospheric temperature, respectively, while \(P\) and \(T\) represent the ambient pressure and ambient temperature. By applying these formulas, the minimum environmental electric fields required for the UPL at different heights can be determined. These values are plotted in Figure 13.  
It can be observed that as the height increases, the \(E_{stab}\) required by the UPL decreases significantly. Specifically, at a height of 20 m, the \(E_{stab}\) is approximately 160 kV/m, while at 50 m, it rapidly drops to 49 kV/m. Therefore, whether the upward leader can develop continuously is primarily determined by the environmental electric field and the height of the building. In other words, taller buildings are more susceptible to lightning strikes. This finding provides valuable insights for the study of urban lightning activity characteristics and the lightning protection of buildings.