Scattering from a land/sea transition

In order to completely characterize the fields of an infinitesimal dipole above a lossy Earth, the effects of any impedance transition or inhomogeneity, such as caused by a river or land/sea interface must be accounted for. In general, geometrical theory of diffraction (GTD) methods have been applied to solve this type of problem, however they are valid only for abrupt transitions. In this paper the perturbation technique is applied to study the effects of a land/sea transition on the total fields of a dipole above an impedance surface. It is shown that the effects of the transition on the total fields is significant for observation distances far from the transition and independent of the gradient of the transition when both source and observation are near the impedance surface.