The properties of intense convective precipitation and their influence on microwave and millimetre-wave propagation-a review and application of new and current information

Three main areas of research measurements are reviewed, each of which relates directly to the determination of characteristic attenuation values in hail. These areas are: 1) the determination of the size distributions of hail and graupel particles, 2) determination of the terminal fall velocity of hail and graupel, 3) determination of the scattering properties of a range of particles which are composed of an ice:water:air mixture. Clearly the modelling problem is difficult because of the diverse nature of hail, both in terms of the complexity of the structure of individual particles and in the variability of hail events. An interesting objective is to provide simplifying formulations which would provide attenuation data for hail events in terms of equivalent rain rates