Electromagnetic wave propagation and scattering in rain and other hydrometeors

Numerical models of interactions between microwaves or mm-waves propagating through fields of hydrometeors are reviewed, with attention given to the problem of earth-space communications. Attenuation occurs in communications links at frequencies above 5 GHz, with the causative agents being rain, snow, or ice crystals at high altitudes. The dielectric properties of the hydrometeor objects are defined and consideration is given to the shape, fall velocity, and behavior of the raindrops, snowflakes, and ice particles in order to model their scattering properties and characterize the bulk attenuation and depolarization properties of the medium containing the hydrometeors. An adaptive depolarization cancellation technique for communications is described, as is remote sensing to determine the type of hydrometeors in the broadcast path. Finally, incoherent scattering effects such as amplitude and phase fluctuation, polarization distortion and bandwidth coherency are investigated.