Far-Field Transient Backscattering by Water Drops

Abstract

Approximations to the far-field, backscattering response for an electromagnetic impulse are shown for two water sphere sizes. For small electrical sizes, the scattering is described by an electric dipole; for large electrical sizes, a combination of reflection from the front interface, creeping waves, and surface currents excited as the impulse moves across the sphere is used. It is shown that transient effects are confined effectively to an equivalent space period of less than six diameters and can be neglected in all operational applications of pulse radar to rain detection.