Deriving microphysical parameters of snow with a vertically pointing Doppler radar

Large uncertainties remain on the retrieving of the snow microphysical characteristics by radar due to the natural variability of the drop size distribution and of the bulk density of ice particles. In this context, a Z-R relationship may not represent this natural variability. In this paper a profiling algorithm (SPA) is proposed in order to derive snow microphysical characteristics, such as ice water content (IWC), mean particle diameter (Dm), equivalent rainfall rate (R) and the N0* parameter of stratiform precipitation. SPA is a profiling algorithm that uses the vertical profile of reflectivity (Z) as input. SPA models the aggregation, which is a major process in the stratiform precipitation. The basic hypotheses needed for SPA are the collision efficiency, the particle density and the number of ice nuclei at the cloud top. Retrieval of SPA using X band and UHF radar data over Canada are presented and compared with co-located drop size distribution measurements. The Doppler measurement is used to validate the retrieval profiles and in particular the bulk density hypothesis.