南京地区雨滴谱参数的详细统计分析及其在天气雷达探测中的应用

雨滴谱包含了降雨的丰富信息，不仅能反映雨滴群的微物理特性，也能反映降雨类型、降雨强度等宏观特性，并且在雷达气象领域也有重要的价值。论文对2015和2016年度南京地区32次降雨过程的雨滴谱资料进行了处理、并对多种雨滴参数进行了详细的统计和分析，拟合了层状云降雨、对流云降雨以及积层混合云降雨的雨滴谱Gamma分布参数。另外，还基于雨滴谱数据拟合了雷达反射率因子Z与降雨强度R的Z-R关系，计算了差分反射率Z_DR、相位常数K_DP以及衰减参数，并利用衰减参数进行了C波段雷达回波的衰减订正试验。结果表明:（1）层状云降雨的各微物理参数比较稳定，积雨云的变化剧烈；层云降雨和积层混合云降雨的中雨滴、积雨云降雨的大雨滴对雷达反射率因子的贡献最大。（2）积雨云降雨的滴谱最宽，层状云降雨的最窄。（3）利用依据雨滴谱数据拟合的三类降雨Z-R关系，可以一定程度地提高雷达估测降雨的精度。（4）利用基于雨滴谱数据拟合的衰减系数，有效地进行了C波段双偏振雷达回波强度的衰减订正，体现了统计参数和拟合参数准确性。

Comprehensive Statistical Analysis of Rain Drop Size Distribution Parameters and Their Application to Weather Radar Measurement in Nanjing

Rain drop size distribution (DSD) contains plenty of information, which reflects not only microphysical characteristics of the rainfall, but also macro-physical properties like rainfall type, rainfall intensity and so on, and has important applications in radar meteorology. In this study, 32 rainfall events data collected by a Parsivel laser spectrometer at Nanjing from 2015 to 2016 are pre-processed and detailed statistics and analysis are conducted. The Gamma-distribution functions of DSD have been fitted for stratiform, convective and mixed-phase rainfall. The Z-R relationships have been established based on the dataset. Polarimetric variables like differential reflectivity Z_DR, specific differential phase K_DP and attenuation parameters are calculated, and the attenuation correction of C-band radar reflectivity factor is tested and validated. The results are as follows. (1) Microphysical variables are less fluctuating for stratiform rainfall, but they vary significantly for cumulonimbus rainfall. Middle-size raindrops contribute more to radar reflectivity and rain rate for stratiform and mixed-phase rainfall, while big-size raindrops make more contributions for cumulonimbus rainfall. (2) The DSD spectral width is the broadest for cumulonimbus rainfall and the narrowest for stratiform rainfall. (3) The accuracy of rainfall estimate from radar measurements can be effectively improved using the fitted Z-R relationship compared to that using the default Z-R relationship. (4) Effective attenuation correction of C-band radar reflectivity factor based on the fitted parameters implies that the DSD statistics and fitting parameters are reliable.