Statistical Characteristics of Summer Season Raindrop Size Distribution in the Western and Central Tianshan Mountains in China

Abstract

 Characteristics of raindrop size distribution (DSD) in summer in the western (Nilek) and central (Urumqi) regions in the Tianshan Mountains of China are studied based on three years of second-generation OTT Particle Size Velocity (Parsivel²) disdrometer data. The FengYun-2G satellite remote sensing data and the ERA5 reanalysis product are used to reveal the dynamical characteristics associated with summer rainfall in Urumqi and Nilek. The DSD in Nilek is significantly different to that in Urumqi. The concentration of mid-size and large size drops is higher in Nilek than in Urumqi. The DSD characteristics for six rain rate classes and two rain types (convective and stratiform) are studied. It is found that the raindrops in Nilek overall have higher mass-weighted mean diameters (D_m) and lower the logarithm of normalized intercept parameters (log₁₀ N_w) than the raindrops in Urumqi, which is true for different rain rates and rain types. Convective clusters in Urumqi are similar to maritime clusters, whereas convective clusters in Nilek are more like continental clusters, according to a classification standard of convective clusters. The radar reflectivity, rain rate relations, and the shape and slope relations for rainfall in Urumqi and Nilek are obviously different. The DSD variability in the two regions may be attributed to differences in convective intensity that are closely related to the specific terrain of the Tianshan Mountains.