Rain Resulting from Melting Ice Particles

Abstract

By means of a zenith-pointing radar, observations were made of the reflectivities and Doppler spectra in orthogonal planes as a dissipating shower exhibiting a bright band passed overhead. The observations have been used to test various procedures for estimating hydrometeor parameters from measurements of radar reflectivitity. They involve assumptions that the raindrop diameters were exponentially distributed, preferably in the manner prescribed by the Marshall-Palmer distribution. It is concluded that, in this case, such an assumption was not valid in regions where it was expected to be valid. As a consequence, estimates of median raindrop diameters and updraft velocities calculated from radar reflectivities were in error. The analyses indicate that raindrop size sorting under the influence of vertical wind shear can account for the observed non-exponential size distributions.