辽宁地区不同降水云系雨滴谱参数及其特征量研究

根据2013—2014年5—10月西安地区观测得到的雨滴谱数据，结合C波段新一代多普勒天气雷达的观测资料，对西安地区43次积层混合云降水的平均雨滴谱分布、微物理特征量及雷达反射率因子Z和雨强R的关系进行统计分析。
结果表明：积层混合云降水的平均雨滴谱呈单峰型，Gamma分布对降水大粒子的拟合明显优于M-P分布；积层混合云中雨滴数浓度最大值及对雨强贡献最大值均出现在雨滴直径小于1 mm的范围内；利用最小二乘法建立了西安地区积层混合云的Z-R关系Z=168R^1.43；当雨滴谱数据计算的回波强度小于（大于）30 dBz，雷达对回波强度有明显高估（低估）现象，针对此现象提出了积层混合云雷达回波的5档修正方案；利用Z=168R^1.43估算西安积层混合云降水个例的降雨量更接近实测降雨量，估算降雨量的相对误差从51.3%减小到25.4%。

Systematic variation of drop size and radar-rainfall relations

Based on the raindrop spectrum data observed in Xi'an, Shaanxi Province from 2013 to 2014, and combined with the observation data of the weather radar, the mean raindrop distribution, the microphysical characteristic quantity and Z-R relationship of 43 precipitation events of the mixed convective-stratiform clouds were statistically analyzed. The results show that the mean raindrop spectrum of the precipitation display a single peak, and the fitting of the Gamma distribution to the large precipitation particles is obviously better than that of the M-P distribution. The drop size corresponding to the peak value of raindrop number concentration and having the greatest contribution to rainfall intensity appeared at less than 1 mm in diameter in the raindrop spectrum. A Z-R relationship Z=168R^1.43 has been established by the least square method for the mixed convective-stratiform clouds in Xi'an area. When the echo intensity calculated from raindrop spectrum data is less than (greater than) 30 dBz, the radar observation can overestimate the echo intensity. With echo intensity decreasing, the radar echo intensity is obviously overestimated (underestimated).
A 5-grade revised scheme for the radar echo is proposed. The Z-R relationship Z=168R^1.43 was used to estimate the rainfall during the precipitation events of the mixed convective-stratiform clouds in Xi'an area. The estimated amount of precipitation is closer to the actually measured rainfall. The relative error of the estimated rainfall was reduced from 51.3% to 25.4%.