Precipitating Hydrometeor Characterization by a CW Doppler Radar

Abstract

The use of small monostatic Doppler radars to identify precipitating hydrometeors has been studied. Monostatic and bistatic configurations were simultaneously tested to select those best suited to the French meteorological network. Calculated and experimental velocity spectra are compared for drizzle, rain, and snow situations. Agreement is observed between the different spectra. Hydrometeor characterization involves the determination of velocity parameters derived from Doppler spectra: spectral peak velocity and standard deviation. A hydrometeor identification diagram drawn up using these parameters allows the system to recognize the main precipitating hydrometeors. Comparisons with human observations give, a detection score of more than 99% for all hydrometeors. For the two configurations, rain and snow identification scores are of the same order, except for the 74% snow score for the monostatic radar. This poorer result has been improved using an additional parameter, the maximum velocity, also derived from the velocity spectrum. The new snow score is 80%; no similar effect has been obtained for other hydrometeor identification scores.