江淮之间夏季雨滴谱特征分析

Analysis of microphysical characteristics of the raindrop spectrum over the area between the Yangtze River and the Huaihe River during summer

分析了2011—2013年夏季(6—8月)滁州地基雨滴谱观测资料,根据雨强及其随时间的变化将降水分成对流降水和层云降水,分析不同降水类型的雨滴谱特征。结果表明:滁州地区对流降水的质量加权直径Dm和标准化参数lg Nw的平均值分别为1.67 mm和3.91 mm-1·m-3,层云降水Dm和lg Nw的平均值分别为1.18 mm和3.57 mm-1·m-3,对流降水雨滴平均尺度更大。Nw相比Γ分布参数N0能更好地反映总数浓度Nt的大小。Γ分布3参数均随雨强的增大而减小,当雨强增长到一定程度时,μ(谱型)和Λ(斜率)趋于常数。研究了μ-Λ关系和Z(反射率因子)-R(雨强)关系。对流降水和层云降水的Z-R关系分别为Z=408R1.20和Z=301R1.21。新的Z-R关系和经典Z-R关系(Z=300R1.40)反演的雨强相比实际观测值均偏小,但新的Z-R关系反演的雨强与实际观测值更接近。

The data of the raindrop spectrum from a ground-based disdrometer at Chuzhou weather station during summers（June to August）of 2011-2013 were analyzed to investigate the characteristics of the raindrop spectrum of different precipitation types.According to the precipitation rate and its temporal variation,the precipitations were divided into the convective and stratiform precipitation.The results show that mass-weighted-averaged diameter（Dm）and normalized intercept parameter（lg Nw）were 1.67 mm and 3.91 mm-1·m-3 for convective precipitation and 1.18 mm and 3.57 mm-1·m-3 for stratiform precipitation,respectively,implying that the convective precipitation was composed of larger drop size than those of the stratiform precipitation.The total number concentration（Nt）has a better relationship with Nwcompared withΓparameter N0.The three parameters of theΓdistribution decreased as the increasing precipitation rate.The shape index（μ）remains constant when the rainfall intensity（R）is large enough.The relationships ofμ-Λand Z（radar reflectivity）-R（precipitation rate）were also discussed.The Z-Rrelationships were Z=408R1.20 and Z=301R1.21 for the convective precipitation and the stratiform precipitation,respectively.The rain rate calculated using both the new and old Z-Rrelations was smaller than the observed rain rate;however,the calculated rain rate using the newZ-Rrelation was closer to the observed rain rate.