基于S波段双偏振雷达和2DVD雨滴谱仪的华南前汛期强降水微物理特征研究

During the first rainy season, South China often experiences frequent occurrences of heavy rainfall, leading to severe meteorological disasters. The current lack of scientific understanding of the microphysics characteristics of heavy precipitation over southern China has seriously restricted its mechanism in-depth analysis and the improvement of numerical forecast. The polarimetric radar has unique advantages in obtaining the precipitation microphysics characteristics. However, there are complex nonlinear relationships between the radar observations and raindrop size distribution parameters, which also have obvious regional differences. It`s difficult to carry out the precipitation microphysics characteristics directly based on radar observations. In order to solve the above problems, this study takes the S-band polarimetric radar in Guangzhou as an example. For the first time, many high-precision 2DVD disdrometers are used during field campaign in southern China to obtain the representative characteristics of the raindrop spectrum. The raindrop spectrum characteristics are applied to build up constrained gamma (C-G) model raindrop size distribution retrieval scheme based on polarimetric radar observations. Then, the relationships between radar reflectivity factor (ZH) and differential reflectivity (ZDR) and three gamma raindrop spectrum distribution parameters will be established to obtain high accuracy spatial and temporal distribution characteristics of raindrop size distributions. Based on the raindrop size distribution retrieval results, the microphysics characteristics of precipitation are calculated and applied to the analysis of microphysics characteristics of heavy precipitation over southern China during the pre-summer rainy season. The characteristics and evolutions of three dimensional precipitation microphysical structures in different development stages of typical heavy rainfall systems will be obtained.

华南前汛期强降水频发，常导致严重气象灾害。当前对华南前汛期强降水微物理特征科学认识上的匮乏，严重制约了对其发生发展机理的深入研究和数值预报水平的提升。双偏振雷达在获取降水微物理特征上有独特优势，但雷达探测量与雨滴谱分布参数之间存在复杂非线性关系，且有明显地域差异性，难以直接用于降水微物理特征研究。针对上述问题，本研究以广州S波段双偏振雷达为例，首次在华南地区采用多台高精度2DVD雨滴谱仪开展观测试验，获取本地区具有代表性的雨滴谱特征。将雨滴谱特征应用到约束伽马（C-G）模型双偏振雷达反演雨滴谱方案中，建立雷达反射率因子（ZH）和差分反射率（ZDR）与伽马雨滴谱分布三个参数之间的关系，获取准确度较高的雨滴谱时空分布特征。基于双偏振雷达反演雨滴谱结果计算得到降水微物理特征量，将其应用到华南前汛期强降水微物理特征研究工作中，获取典型强降水天气系统不同发展阶段的三维降水微物理结构特征及其演变规律。

华南地区前汛期强降水频发，常导致严重气象灾害。目前对华南前汛期强降水的研究取得了一定的进展，但仍存在很多科学问题尚未解决，尤其是对强降水天气系统微物理结构特征及演变规律的科学认识上仍存在很大不足。相比于多普勒天气雷达，双偏振雷达新增探测量与降水粒子微物理特征存在联系，但这种关系是复杂非线性的，且有明显地域差异性。针对上述问题，本项目基于中国气象局龙门云物理野外科学试验基地多台2DVD雨滴谱仪首次在华南地区开展观测试验，得到降水粒子尺寸-轴比关系和尺寸-下落末速度关系。在此基础上，优化S波段双偏振雷达资料正演观测算子，提高模拟双偏振雷达量模拟精度。首次基于2DVD雨滴谱仪获取华南地区伽马雨滴谱分布谱形参数-斜率参数相关关系。采用约束伽马方法，通过S波段双偏振雷达探测量：ZHH和ZDR，构建双偏振雷达反演伽马雨滴谱三参数方案。经过飑线、暖区暴雨、季风降水等多个暴雨过程检验结果表明，S波段双偏振雷达雨滴谱反演结果与临近2DVD雨滴谱仪观测结果较为接近，相对误差小于10%，反演方案精度较高。该反演方案建立了双偏振雷达探测量与雨滴谱参数之间的关系，有力推动双偏振雷达探测资料在模式预报效果评估以及对流尺度资料同化等方面的研究和应用工作。基于上述反演方案，系统研究了华南前汛期2017年“5.7”和“6.22”两次典型强降水过程不同发展阶段的三维降水微物理结构特征及其演变规律。研究结果表明，“5.7”过程以暖云降水为主，冰水含量极低，具有明显低质心特点。雨滴有效粒径和数浓度均明显高于“6.22”过程。“6.22”特大暴雨过程的冰水含量要明显高于“5.7”特大暴雨过程，而最终降水强度却接近，这说明“6.22”过程中冰相过程有助于产生强降水。该方案已应用于广东省人影中心业务系统中，评估广东省人影飞机作业和人影火箭作业效果。依托本项目研究成果，共发表9篇学术论文，其中SCI(E)论文5篇。获得1项软件著作权。本项目共培养2人晋升高级职称，1人晋升中级职称，培养1名硕士研究生。