To Understand the characteristics of the solid precipitation particles (i.e. snow and graupel) using polarimetric radars, it is necessary to clarify the relationship between proparties of particles and the polarimetric parameters (Zh, Zdr, Kdp, ρ_hv). In this study, we examine the relationship polarimetric parameters obtained by a radar at Oshimizu, Ishikawa Prefecture to properties of solid precipitation particles (categories, diameters, shapes and number concentrations) observed by a ground-based imaging system at Kanazawa University during the winter of 2008-2009.

Particle categories are classified using complexities and number of holes obtained from each particle-image. ”Undetectable particles” are also categorized, because small particles cannot be separated using these indices. Categories (snow or graupel) and typical characteristics of predominant particles are determined using shapes, diameters and volumes. The target area is prescribed by expecting that particles fall into the ground-based observation system from an observation hight of the lowest PPI elevation angle (0.6 ) with considering wind direction and speed in the lower troposphere and particles fall velocity. We compare with mean values of poalrimetric parameters in the area and properties of particles.

We analysed data for periods: at 1900 JST-2100 JST on 13 Jan 2009, at 1300 JST-1500 JST on 15 Jan 2009 and at 2100 JST-2130 JST on 16 Feb 2009. In these piriods, we determined four graupel cases (G1-G4) and four snow cases (S1-S4). Graupel particles have conical or round shapes whose diameter are 3-6 mm. Snow particles are snowflakes whose diameter are 6-15 mm. During the graupel periods (G1-G4), polarimetric parameters Zh, Zdr, Kdp and ρ_hv ranged 19.9 - 31.2 dBZ, -0.6 - -0.1 dB, -0.3 - 0.1 =km and greater than 0.99, respectively. During the snow periods (S1-S4), values of four parameters are 14.9 - 27.2 dBZ, -0.5 - -0.2 dB, -0.2 - 0.3 =km, more than 0.99, respectively. Although diameters of graupel are smaller than those of snow particles, Zh during the graupel periods is greater than that during the snow periods. This should depend on a relationship particles density and reflectivity of electric wave. Others parameters (Zdr, Kdp, ρ_hv)are similar between the graupel and snow periods. Large Zh is obtained when graupel particles whose diameter or number concentration are great by the ground-based observation system. When graupel and snow particles are coexistent in a target area, Zh has lower value because of the existence of longitudinal graupel particles during the snow period. High Kdp value during the snow period, corresponds to the many undetectable particles, since Kdp is sensitive to noncircular particles.

A hydrometeor classification is conducted into two graupel cases. The existence of graupel cannot be identified in one of the graupel case. Value of ohters parameters (Zdr, Kdp,ρ_hv) are ranged in the categories of graupel. A lower range of Zh in the membership function should be extended to less than 30 dBZ to detect the existance of graupel in this case. are ranged in the categories of graupel. A lower range of Zh in the membership function should be extended to less than 30 dBZ to detect the existance of graupel in this case.