基于二维视频雨滴谱仪和双偏振雷达观测的华南定量降水估计研究

High resolution high precision radar quantitative precipitation estimation(RQPE) plays an important role in hydrology simulation and prediction、flood and disaster prevention and relief as well as nowcasting weather service, and has valuable implications for the society. Raindrop size distribution (DSD) is the basic characteristics of precipitation microphysics. It describes the distribution of falling particles as a function of diameter. The relationships between characteristics of raindrop’s shape, velocity and DSD and radar variables are the key of RQPE. This proposal plans to make use of observations from seven 2D video distrometers to analyze the characteristics of DSD over southern China according to different precipitation classes in different periods. Then the relationships between radar variables and precipitation rate are derived based on the DSD characteristics. With these localized relationships, the region-based hydrometeor classification based on fuzzy logic and QPE (RBQPE) and QPE based on specific attenuation of radar signal (RAQPE) are applied to improve the accuracy of the dual-pol radar QPE over Southern China. Experiment with DSD sample data and radar observations from Zhuhai and Guangzhou S-band dual-pol radar shows that the proposed DSD analysis, RBQPE, and RAQPE are feasible. The main content of this proposal includes: 1)the DSD characteristics of different precipitation types in different precipitation systems in different seasons over southern China; 2) relationship between dual-polarimetric radar varables and precipitation rate; 3)QPE computation based on relationship between dual-polarimetric varables and precipitation rate. This proposal is expected to give references and technic supports to upgrade of China Next Generation Weather Radar with dual-polarization capability in coming future.

高分辨率高精度雷达定量降水估计在水文模拟预报、防洪抗灾和气象短临预警预报方面具有重大科学意义和社会价值。降水雨滴谱是降水微物理的基本特征，描述降落雨滴的粒径分布特征。雨滴的形状、下落速度和谱分布等特征与雷达回波的相关关系是雷达定量降水估计的基础。本项目基于7部高精度二维视频雨滴谱仪和8部双偏振雷达观测，分析华南前汛期、后汛期、冷季内不同降水系统（飑线、台风、准静止锋及其他）的层云、对流、浅层等降水类型的雨滴谱特征，计算适用于华南不同时期不同降水系统的双偏振雷达变量和降水率的关系式，采用基于区域的水凝物模糊逻辑分类以及基于雷达信号衰减的双偏振雷达定量降水估计算法，研制华南高分辨率高精度的雷达定量降水估计产品。研究内容主要包括：1）不同时期内不同降水系统不同降水类型的雨滴谱特征；2）双偏振雷达变量和降水率的关系式；3）基于区域水凝物模糊逻辑分类和基于雷达信号衰减的双偏振雷达定量降水估计。

针对双偏振天气雷达在欧美日国家成为气象灾害监测和预报预警的重要观测手段这一背景，本项目的研究内容为：利用中国华南地区的高精度雨滴谱观测资料和双偏振天气雷达观测资料，研究：1）研究了华南冷季、前汛期（4-6月）、后汛期（7-10月）、不同季节的雨滴谱特征，以及台风、飑线的雨滴谱特征；2）给出了华南地区不同季节双偏振雷达变量和降水率的关系式；3）研发面向对象（即基于区域水凝物模糊逻辑分类）和基于雷达信号衰减的双偏振雷达定量降水估计算法；4）研究了粤港澳大湾区X波段双偏振相控阵天气雷达的衰减订正算法; 5)发展了基于物理约束和改进的变分法进行双偏振雷达的Φ_DP重构和非负KDP获取； 6)基于雷达观测和深度学习的短临降水预报模型. 研究结果表明：1）当降水率小于5 mm/h时，后汛期和前汛期降水的发生频率几乎一致,而随着降水率的增大（5-30 mm/h），后汛期降水的发生率略微高于前汛期, 但当降水率大于30 mm/h时，前汛期降水的发生率则高于汛期，说明华南地区的前汛期强降水的发生率略微高于降水；2）基于华南的雨滴谱观测数据计算出来的雷达变量和降水率的关系式明显不同于美国国家大气海洋管理局提供的常用的Z-R关系式；3）研发的基于区域水凝物模糊逻辑分类和基于雷达信号衰减的双偏振雷达定量降水估计算法明显提高了双偏振雷达定量降水估计的精度；4）研究的X波段双偏振相控阵天气雷达的衰减订正算法明显改进了珠三角X波段双偏振相控阵天气雷达降水定量降水估计精度; 5)基于雷达观测和深度学习的短临降水预报模型比当前气象部门主流的光流法和Unet预报模型具有更好的预报技巧。上述双偏振雷达定量降水估计算法、质控算法、短临预报模型在提高粤港澳大湾区防灾减灾应急服务水平具有重要的应用前景。

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