雨滴谱是云及降水物理学中重要的研究对象,基于北京2015年8月7日的强降水雨滴谱观测数据,计算得到该过程的雨滴谱、质量加权直径、平均直径等雨滴 尺寸分布特征,由雨滴谱观测数据计算得到降水强度、液态水含量和雷达反射率,分析这些降水参数在此次降水过程中的变化特征。综合分析雨滴谱参数 和S波段天气雷达反射率表明此次降水过程具有飑线特征,可划分为前端的引导对流性降水、过渡降水和尾部层状降水三个阶段。最后讨论不同降水阶段 雨滴谱参数及降水参量的变化及其对雷达定量降水估测Z-R关系的影响。结果表明对流性降水阶段的雨滴数浓度(大于4600个/m3)、 质量加权直径(2.69 mm)、最大直径(6.3 mm)均远高于过渡和层状降水阶段,对流降水阶段和过渡阶段雨滴直径分布范围类似(标准差均大于0.3 mm), 层状降水分布较窄(标准差0.24)。不同降水阶段拟合得到的Z-R关系明显不同,拟合得到此次降水整个过程的Z-R指数经验关系系数a=674.91,指数b=1.39。

Raindrop size distribution (DSD) plays an important role in microphysics of clouds and precipitation. A case study about a heavy rainfall with squall line characteristic passing through Beijing is presented by analyzing the DSD observation data. The variability of DSD and induced rainfall parameters in different rain regimes, namely initial convective rain, transition and trailing stratiform, is investigated. Compared with the transition and trailing stratiform region, leading convective line is characterized by large raindrop concentrations(>4600 counts/m3), large mass-weighted mean diameter(2.69 mm), and maximum drop size(6.3 mm). Convective and transition regime have the similar DSD with standard deviations(>0.3 mm), wider than stratiform region(>0.24 mm). The empirical Z-R relationships are conspicuously different between different rain phases.