Possibility of Solid Hydrometeor Growth Zone Identification Using Radar Spectrum Width

In this study, the correlation between simulated and measured radar velocity spectrum width ( σ v ) is investigated. The results show that the dendrites growth zones (DGZs) and needles growth zones (NGZs) mostly contain dendrites (DN) and needles (NE), respectively. Clear σ v zones (1.1 < σ v (m s −1 ) < 1.3 and 0.3 < σ v (m s −1 ) < 0.7 for the DGZ and NGZ, respectively) could be identified in the case studies (27 and 28 February 2016) near altitudes corresponding to temperatures of −15°C and −5°C, according to the Japan Meteorological Agency and mesoscale model reanalysis data. Oblate particles with diverse particle shapes were observed in the DGZ with σ V > 1.2 m s −1 , a differential reflectivity (Z DR ) higher than 0 dB, and a cross-correlation coefficient ( ρ hv ) less than 0.96. In contrast, prolate particles with relatively uniform shapes were observed in the NGZ with σ v < 0.6 m s −1 , a Z DR less than 0 dB, and ρ hv higher than 0.97. The simulation results show that the DN exhibited a larger σ v compared to the NE, and this observed σ v was strongly dependent on the wind fluctuations ( v ’) due to turbulence or wind shear. In contrast, the NE exhibited a significantly small σ v ∼ 0.55 m s −1 , which converges irrespective of v ’. In addition, a strong correlation between the measured σ v values at five radar elevation angles ( θ = 6.2°, 9.1°, 13.1°, 19°, and 80°) and those simulated in this study confirmed the significance of the analysis results.