Lightning represents a frequent natural hazard that severely compromises the safety and reliability of power systems. Current lightning location and inversion methodologies predominantly rely on idealized flat terrain models, while existing research on topographic effects has primarily examined isolated mountain configurations. To bridge this critical knowledge gap, this investigation develops a comprehensive finite-difference time-domain (FDTD) framework incorporating realistic multi-peak terrain features. Through systematic parameterization studies, the model evaluates how variations in mountain elevation and sensor placement affect both temporal and amplitude characteristics of lightning electromagnetic fields. The findings reveal that electric field attenuation at foothill-proximal observation points is overwhelmingly dominated by outer mountains, achieving maximum attenuation of 97.28%. Furthermore, propagation delays exhibit significantly greater sensitivity to outer mountains than to intermediate terrain features across both foothill and distant observation locations. Outer mountain elevations of 1000 m amplify time delays by factors of 2.01 at the distant observation points, while intermediate elevations below the lightning strike height demonstrate negligible impact.