中国东部地区降水雨滴谱的季节变化特征及其环境影响因子分析

Fully recognizing the variability of raindrop size distribution (DSD) is of great importance for understanding precipitation microphysics and its parameterization, improving radar quantiative precipitation estimation (QPE) and model forecasting. With the optimal use of observations from advanced disdrometers and other environmenal detection facilities, the objective of this proposal is to understanding the seasonal variations of raindrop size distribution in Eastern China, and further revealing their environmental impact factors. The high-precision 2D video disdrometer (2DVD) and vertically pointing micro rain radar (MRR) datasets are firstly used to investigate the seasonal variation of raindrop size distribution and the differences in related rainfall vertical structure. Based on the observed DSD characteristics, improved and/or newly-built DSD-derived relationships, including shape-slope relation of Gamma-DSD model, raindrop fall velocity-diameter relation, raindrop axis ratio relation, and QPE relations will be obtained for precipitation in this specific region. These relationships will further be applied for the retrieval of DSD and rainfall from dual-polarization/ multi-frequency radar observations, the construction of scattering matrix of raindrop, and the improvement of model paramterization. Moreover, the enviromental parameters, from both natural conditions and anthropogenic activities, are calculated from collocated observation along with disdrometers. Thse parameters are further used to quantitative analyze their impacts on the variation of DSDs and the dominant influence mechanisms. This study will also help to provide the theoretical and experimental support for the quantitative application of the sattelite-based dual-frequency precipitation radar and the ground-based national network of dual-polarization upgraded operational CINRAD radars in China in the future.

充分认识雨滴谱特征变化对于理解降水微物理过程、提高雷达定量降水估计、改进模式微物理参数化和预报精度具有重要的作用。本项目利用多种雨滴谱仪和环境观探测设备的联合观测资料，对我国东部地区降水微物理的季节变化特征及其环境影响因子进行研究。高精度二维视频雨滴谱仪2DVD和垂直指向微降雨雷达MRR的观测数据将首先用于揭示雨滴谱的季节变化特征及其对应的垂直结构差异；基于雨滴谱的变化特征，改进和建立本地化的雨滴谱导出关系和物理模型（包括Gamma分布函数的形状-斜率关系、雨滴降落末速度-粒径关系、轴长比关系、降水估计关系、QPE关系等），应用于雷达定量降水估计、雨滴谱反演，以及模式参数化方案的改进等；同时，利用环境变量的联合观测，揭示主导降水微物理特征变化的环境影响因子（包括自然条件和人为因素）及其影响机制。本项目研究也为未来我国的星载双频降水雷达及业务双偏振雷达网的资料定量应用提供理论和实验依据。

充分认识降水雨滴谱的变化特征，对于提高本地化雷达定量降水估计和模式微物理参数化描述的精度，以得到更精确的降水预报至关重要。降水雨滴谱特征在不同降水类型、不同气候区和不同地形下均具有很大的时空变化，且该特性受局地气溶胶等多种环境因素的调控，并与其降水微物理结构和过程的差异密切相关。为准确认识中国东部地区独特季风背景下的降水雨滴谱变化特征及其对应的降水系统内部相态、结构特征等的变化规律，揭示外部环境因素的主导影响及机制，开展本项目研究。首先，通过多种雨滴谱探测仪器、双偏振多普勒天气雷达、GPM降水卫星以及细颗粒物检测仪、风廓线雷达等的环境变量联合观测，构建了中国东部地区长时间高精度的降水雨滴谱和环境变量样本库；其次，开展了降水雨滴谱的不同季节、不同季风期以及季风推进过程中的变化特征研究。利用地面雨滴谱仪和GPM卫星资料揭示了不同季节的降水雨滴谱和垂直结构特征，系统分析了闽南前汛期爆发前后的雨滴谱变化特征、江淮梅雨期降水垂直结构的统计特征及梅雨锋面和暖区极端降水的差异，以及季风从前汛期至梅雨期向北推进过程中的微物理变化特征等；最后，结合雨滴谱和环境参数的长时间联合观测，开展了环境因素对雨滴谱变化特征的影响分析，揭示主导降水微物理特征变化的主要环境影响因子及其影响机制，在此基础上对基于环境变量的雨滴谱机器学习预测进行了可行性探讨。本研究全面而系统地揭示了我国东部地区不同季节/季风期的降水微物理变化特征及其主导过程和主导环境因素，改进和建立了本地化雨滴谱导出关系和物理模型，相关成果促进了对我国东部地区降水微物理特征和变化规律的认识，能够有效应用于本地化降水估计和预报能力提升，也为未来我国星载双频降水雷达、升级后的业务双偏振天气雷达网、已完成的全国降水现象仪观测网的资料定量应用，以及基于大数据、机器学习等的传统/新型数值预报模式研究提供理论和实验依据。