| Polarimetric radar is a very useful tool for remote sensing of storm microphysics. Multiparameter radar data have been used extensively in the interpretation of microphysical evolution of convective storms. However, the interpretation of polarimetric radar measurements become complicated in the case of winter precipitation where the hydrometeors can exist at different altitudes with varying sizes, shapes, orientations and bulk densities. Colorado State University operates a fully polarimetric, S-band Doppler radar (CSU-CHILL radar). The CSU-CHILL radar was used to collect coordinated data from winter precipitation. The measurement set include radar reflectivity factor at horizontal and vertical polarization (ZHH,VV), differential reflectivity (ZDR), specific differential propagation phase (phiDP), linear depolarization ratio ( LDR), and co-polar correlation between horizontal and vertical polarizations states (rhoHV).; During the winter of 1996--1997, multiparameter radar measurements using CSU-CHILL radar were collected over several snow storms in conjunction with in-situ observations. These radar data were used to study the microphysical characteristics of the different hydrometeors comprising these storms including intensity, habit, and bulk density. Microphysical structure and time evolution were also studied using these data. The in-situ observations include data obtained using a 2D-video disdrometer on the ground as well as airborne measurements collected by the Wyoming King Air (WKA) aircraft which was equipped with PMS FSSP, 1D-C, 2D-C, and 2D-P probes, as well as a full set of navigation, air motion, and thermodynamic instrumentation. The 2D-video disdrometer located on the ground was used to obtain two views of each precipitation particle entering the sensor area and its fallspeed. The 2D particle imaging probes mounted on the WKA were used to get images of particles passing through the sampling area along its track. These data were used to obtain the particle size distributions and evidence of particle type. A weighing type snow gauge located nearby also provided measurements of snow accumulation. One of the first results of winter precipitation using a combined study of multiparameter radar and in-situ measurements such as 2D-video disdrometer, and instrumented aircraft is presented. Data from several winter precipitation events are studied to provide microphysical interpretation of the radar signatures, and infer hydrometeors densities.; A model for radar backscatter, considering particle types, shapes, sizes, orientations, and densities is used, providing a framework for microphysical interpretation and for comparing the radar signatures and in-situ observations. Based on the intercomparison study, a procedure to estimate bulk density of ice particles is developed, demonstrating the application of multiparameter radar measurements in microphysical interpretation. |
