Microphysical Characteristics of Warm-Season Precipitation in Eastern Coastal China

Abstract

This study investigates the microphysical characteristics of warm-season precipitation with observations from the second generation Parsivel disdrometer OTT2 in Ningbo, situated in eastern coastal China. A comparative analysis is conducted on the raindrop size distribution (DSD) across various rain types and regions, with a focus on elucidating the relationships between different rain rate (R), raindrop sizes, concentrations, and radar reflectivity (Z). Moreover, this study meticulously analyzes the shape-slope (μ−Λ) relationship of raindrops during the warm season in this region. The results reveal that during warm-season convection in coastal eastern China, the mass-weighted mean diameter (D_m) and the logarithmic generalized intercept parameter (log₁₀ N_w) are 2.21 mm and 3.51, respectively. This indicates the presence of low-concentration large raindrops, distinguishing this region from other parts of China such as Guangdong, Hubei, Nanjing, and Beijing. Additionally, the enhancement of convective R is predominantly driven by the increase in raindrop size. Convective rainfall accounts for 67.0 % of the total precipitation, while stratiform contributes 11.1 %. Both types of rain display a unimodal distribution in number concentration and diameter, peaking at 0.3–0.6 mm. Additionally, both generally follow the three-parameter Gamma distribution, despite minor deviations in the occurrences of larger and smaller raindrops. The μ−Λ relationship in eastern coastal China is similar to that of the southern coastal regions, both being dominated by large raindrops. The Z–R relationship for warm-season convection is expressed as Z = 396.96R^1.34. These findings are vital for optimizing regional model cloud microphysics parameterization and improving the precision of local radar-based quantitative precipitation estimates.