A New Approach to Backscattering of Pulsed Beam Waves from Hydrometers

This paper deals with the backscattering of millimeter pulsed beam waves from hydrometeors. A new approach is presented for a solution of the time-dependent three dimensional vector radiative transfer equation for the Stokes vectors to discuss the multiple scattering effects of beam waves on radar echoes. General solutions including multiple scattering for beam waves are then derived explicitly in an integral form without any approximation. Time dependent second-order solutions for the radar echoes of pulsed beam waves are obtained to predict the multiple scattering effects depending on the variation in an incident beam size. It is shown that the inhomogeneity of the radial direction of beam waves causes the mode coupling of waves between the azimuth directions in the scattering matrix and that the mode coupling depends on the ratio of the incident beam size to the mean free path length of the medium.