对流性降水雨滴谱特征及其与雷达反射率因子的对比分析

Comparative analysis on rain spectrum characteristics of deep convective cloud and its radar reflectivity

利用OTT Parsivel激光降水粒子谱仪观测的南京地区梅雨季节对流性降水过程的雨滴谱资料和江苏省气象台龙王山雷达观测资料,结合天气形势,对梅雨季节对流性降水过程的微物理参量、平均雨滴谱和速度谱分布特征进行分析;在对平均谱拟合时发现,Gamma分布对小滴数目的估计和大滴端形状的符合程度效果好于M-P分布和对数正态分布,并且拟合了Gamma分布参数μ和λ的二次项关系;建立了雷达反射率因子与雨强的相关关系,并将Parsive激光降水粒子谱仪观测计算的回波强度与雷达观测的回波强度作以比较,结果表明:对于此次暴雨过程,雷达观测到的回波强度有低估的现象,并且Parsivel粒子激光探测仪观测计算的回波强度越大,雷达低估的现象越为明显。回波修正后,用统计的Z-I关系式估算的降水量与Parsivel测得的降水量更为接近。

The data of rainstorm process during Meiyu season in Nanjing observed by the Parsivel la- ser precipitation particle spectrometer and s-band Doppler weather radar were used to analyze the charac- teristics of the microphysical parameters, average raindrop size distributions, and raindrop velocity distri- butions. To fit the observed raindrop size distributions, Gamma distribution is better than M-P and log- normal distribution, for estimate of the number of small rain drops and the shape of large rain drops side, then the quadratic relationship between Gamma distribution parameters μ and A was set up. We estab- lished the relationship between radar reflectivity factor and rainfall intensity, and compared echo intensity observed by radar and calculated from Parsivel, the results showed： for the rainstrom, the radar observa- tion could underestimate the echo intensity, and with echo intensity increase, the underestimation was more obvious. After amending, the estimated precipitation by Z-I relationship was closer to Parsivel measurement, it enhanced the accuracy of precipitation estimate by Doppler radar.