Validation of the FDTD method for lightning electromagnetic fields computation in the presence of mixed propagation path with slope-angle

In this paper, we evaluate theoretically the electromagnetic fields radiated by lightning in the presence of compound propagation path (land-ocean) with slope-angle. The electromagnetic fields are calculated by the use of the Finite-Difference Time-Domain method (FDTD) for solving the Maxwell's equations, above and under-ground and for different values of the slope angle. The results are compared with those published in the literature, obtained with the Finite-Elements Method (FEM). The results show that the FDTD method is a very effective approach in the modeling of geometries with slope angles, and that taking into account the slope-angle of the interface land- ocean is very important, where its effect is clearly visible on the electromagnetic fields of lightning.