Forward and backward scattering from liquid and solid hydrometeors of arbitrary orientation

The paper examines the applicability of the Rayleigh approximation (Van der Hulst, 1957) in both the forward and backward scattering direction for raindrops, hails and ice crystals of various shapes and sizes. The validity of the Rayleigh approximation is discussed in some detail. Rules enabling forward and backward scattering at any angle to be generated simply from on-axis scattering amplitudes are given and shown to be generally valid for various scattering approximations in the forward direction but far less general in the backward direction. The use of the Rayleigh approximation to interpret radar returns from hydrometeors and to determine their size, shape, orientation and constituents must be viewed as highly suspect.