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.