Statistical Analysis on the Estimations of Solid Hydrometeors Growth Zones and Their Weather Conditions Using Radar Spectrum Width

Abstract. This study analyzes the correlation between hydrometeor type and radar spectrum width (σ_v) according to wind speed that can occur the atmospheric disturbances such as turbulence and wind shear. The σ_v zones shown as peak values were identified only in stratiform precipitation and they are highly related to the hydrometeor growth zones. Statistical analysis was performed for eight precipitation cases under various conditions (precipitation type, season), focusing on the Dendrite Growth Zone (DGZ) and the Needle Growth Zone (NGZ), where Dendrite (DN) and Needle (NE) type snowflakes are dominant, respectively. They were determined by the Growth Zone Determination Algorithm (GZDA) that was proposed in this study.

The intensity of the σ_v depends on atmospheric conditions (i.e., wind speed) and season (i.e., temperature). The high σ_v and negative relationship with the differential radar reflectivity (Z_DR) in the DGZ for all cases is consistent with the aerodynamic properties of DN. As the range of σv was larger than that of Z_DR, it was confirmed that the dependence of σ_v according to atmospheric conditions is significant. Contrastingly, the NGZ had a low σ_v and weak σ_v-Z_DR negative relationship with a narrow range of σ_v, which is consistent with the aerodynamic properties of NE. The lower cross-correlation coefficient (ρ_hv) in the DGZ than that in the NGZ implies that the irregularities (particle shape and aerodynamics features) of DN were more pronounced than those of NE.

Finally, as the altitudes of two growth zones were determined by temperature, the possibility of estimating sub-zero temperature by GZDA was confirmed.