Multiparameter radar and in situ aircraft observation of graupel and hail

Documenting simultaneous multiparameter radar observations of precipitation in conjunction with in situ hydrometeor sampling is important for the interpretation of multiparameter radar observations. In situ observation using aircraft-mounted probes is one of the best ways to collect such data. In situ observation of hail and graupel in convective storms is complicated due to adverse environment of flight and low concentration of large particles that are difficult to sample. This paper presents one of the first observations of simultaneous multiparameter radar observations and in situ samples of wet hail and graupel in convective storms. The observations are unique because of the excellent coordination between aircraft samples and radar scanning, as well as relatively large sample volumes of aircraft data. Multiparameter radar observations (namely reflectivity, differential reflectivity, linear depolarization ratio, copolar correlation coefficient, and specific differential phase) are documented in graupel and wet hail. The observations indicate that the linear depolarization ratio and copolar correlation measurements, in conjunction with reflectivity levels, can be used to distinguish between graupel and hail. A simple procedure is developed to estimate the average bulk density of graupel and wet hail, comparing radar and in situ observations.