Remote sensing of path-averaged raindrop size distributions from microwave scattering measurements

A multichannel microwave propagation experimental system with frequencies of 1.7, 11.5, 34.5, and 81.8 GHz, is presented for measuring copolar attenuation and phase shift of centimeter and millimeter waves due to rain, as well as for inferring path-averaged raindrop size distribution N(D) from these measurements. The experimental system, which consists of five subsystems and includes a radio wave system and a distrometer, is described. The measurements constitute a Fredholm integral equation of the first kind which for the N(D) was solved numerically by several inversion techniques, and the results were compared with each other. The feasibility of the remote sensing of path-averaged raindrop size distribution from the microwave scattering measurements was clarified.