Electric fields at the top of tall building associated with nearby lightning return strokes

Using the finite-difference time-domain (FDTD) method for solving Maxwell’s equations, we have calculated the vertical electric field Ez due to lightning return strokes both in the presence and in the absence of building at the field point. Strikes to both flat ground and tall objects of height h=100, 200, or 500 m are considered. The magnitude of Ez is significantly influenced by the presence of either building at the field point or strike object. In the case of a lightning strike to flat ground, the magnitude of Ez on the roof of building having a plan area of Sb=40 × 40 m2 and a height of hb=20, 50, or 100 m located at a horizontal distance ranging from d =100 to 500 m from the lightning channel is about 1.5, 2, or 3 times, respectively, greater than that at the same horizontal distance on the ground surface in the absence of building. The enhancement factor for Ez due to the presence of building at the field point is essentially not influenced by the presence of strike object (up to 500 m in height).